Showing papers on "Energy conversion efficiency published in 2018"
TL;DR: Recent progress in addressing stability, how to allow mass production, and how to maintain uniformity of large-area films are reviewed, and the remaining challenges along the pathway to their commercialization are discussed.
Abstract: BACKGROUND Perovskite solar cells (PSCs) have attracted intensive attention because of their ever-increasing power conversion efficiency (PCE), low-cost materials constituents, and simple solution fabrication process. Initiated in 2009 with an efficiency of 3.8%, PSCs have now achieved a lab-scale power conversion efficiency of 23.3%, rivaling the performance of commercial multicrystalline silicon solar cells, as well as copper indium gallium selenide (CIGS) and cadmium telluride (CdTe) thin-film solar cells. Thousands of articles related to PSCs have been published each year since 2015, highlighting PSCs as a topic of intense interest in photovoltaics (PV) research. With high efficiencies achieved in lab devices, stability and remaining challenges in upscaling the manufacture of PSCs are two critical concerns that must be addressed on the path to PSC commercialization. ADVANCES We review recent progress in PSCs and discuss the remaining challenges along the pathway to their commercialization. Device configurations of PSCs (see the figure) include mesoscopic formal (n-i-p) and inverted (p-i-n) structures, planar formal and inverted structures, and the printable triple mesoscopic structures. PCEs of devices that use these structures have advanced rapidly in the case of small-area devices (~0.1 cm 2 ). PSCs are also attracting attention as top cells for the construction of tandem solar cells with existing mature PV technologies to increase efficiency beyond the Shockley-Queisser limit of single-junction devices. The stability of PSCs has attracted much well-deserved attention of late, and notable progress has been made in the past few years. PSCs have recently achieved exhibited lifetimes of 10,000 hours under 1 sun (1 kW/m 2 ) illumination with an ultraviolet filter at a stabilized temperature of 55°C and at short-circuit conditions for a printable triple mesoscopic PSCs. This irradiation is equivalent to the total irradiation of 10 years of outdoor use in most of Europe. However, within the PSC community, standard testing protocols require further development. In addition, transparency in reporting standards on stability tests needs to be improved; this can be achieved by providing both initial photovoltaic performance and normalization parameters. The upscaling of PSCs has also progressed steadily, leading to PSC mini-modules, standard-sized modules, and power systems. PV companies have set out to manufacture large-area PSC modules (see the figure), and a 110-m 2 perovskite PV system with screen-printed triple mesoscopic PSC modules was recently debuted. Studies of these increased-area modules and systems will promote the development of PSCs toward commercialization. PSC research is expanding to cover fundamental topics on materials and lab-sized cells, as well as to address issues of industrial-scale manufacturing and deployment. OUTLOOK The PV market has been continuously expanding in recent years, bringing opportunities for new PV technologies of which PSCs are promising candidates. It is imperative to achieve a low cost per watt, which means that both efficiency and lifetime need improvement relative to current parameters. The efficiency gap between lab cells and industrial modules has seen impressive reductions in crystalline silicon; PSCs must similarly enlarge module areas to the panel level and need to achieve lifetimes comparable to those of legacy PV technologies. Other improvements will need to include industry-scale electronic-grade films, recycling methods to address concerns regarding lead toxicity, and the adoption of standardized testing protocols to predict the operation lifetime of PSCs. Modules will need to endure light-induced degradation, potential-induced degradation, partial-shade stress, and mechanical shock. The field can benefit from lessons learned during the development of mature PV technologies as it strives to define, and overcome, the hurdles to PSC commercial impact.
1,160 citations
TL;DR: Tao et al. as discussed by the authors discuss the development of the key components for achieving high-performance evaporation, including solar absorbers and structures, thermal insulators and thermal concentrators.
Abstract: As a ubiquitous solar-thermal energy conversion process, solar-driven evaporation has attracted tremendous research attention owing to its high conversion efficiency of solar energy and transformative industrial potential. In recent years, solar-driven interfacial evaporation by localization of solar-thermal energy conversion to the air/liquid interface has been proposed as a promising alternative to conventional bulk heating-based evaporation, potentially reducing thermal losses and improving energy conversion efficiency. In this Review, we discuss the development of the key components for achieving high-performance evaporation, including solar absorbers, evaporation structures, thermal insulators and thermal concentrators, and discuss how they improve the performance of the solar-driven interfacial evaporation system. We describe the possibilities for applying this efficient solar-driven interfacial evaporation process for energy conversion applications. The exciting opportunities and challenges in both fundamental research and practical implementation of the solar-driven interfacial evaporation process are also discussed. The thermal properties of solar energy can be exploited for many applications, including evaporation. Tao et al. review recent developments in the field of solar-driven interfacial evaporation, which have enabled higher-performance structures by localizing energy conversion to the air/liquid interface.
1,139 citations
TL;DR: An optimized two-step deposition process allows the formation of uniform layers of metal halide perovskites on textured silicon layers, enabling tandem silicon/perovskite solar cells with improved optical design and efficiency.
Abstract: Tandem devices combining perovskite and silicon solar cells are promising candidates to achieve power conversion efficiencies above 30% at reasonable costs. State-of-the-art monolithic two-terminal perovskite/silicon tandem devices have so far featured silicon bottom cells that are polished on their front side to be compatible with the perovskite fabrication process. This concession leads to higher potential production costs, higher reflection losses and non-ideal light trapping. To tackle this issue, we developed a top cell deposition process that achieves the conformal growth of multiple compounds with controlled optoelectronic properties directly on the micrometre-sized pyramids of textured monocrystalline silicon. Tandem devices featuring a silicon heterojunction cell and a nanocrystalline silicon recombination junction demonstrate a certified steady-state efficiency of 25.2%. Our optical design yields a current density of 19.5 mA cm−2 thanks to the silicon pyramidal texture and suggests a path for the realization of 30% monolithic perovskite/silicon tandem devices.
990 citations
TL;DR: Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability and success in suppressing hysteresis and record efficiency for planars-type devices using EDTA-complexed tin oxide (SnO2) electron-transport layer.
Abstract: Even though the mesoporous-type perovskite solar cell (PSC) is known for high efficiency, its planar-type counterpart exhibits lower efficiency and hysteretic response. Herein, we report success in suppressing hysteresis and record efficiency for planar-type devices using EDTA-complexed tin oxide (SnO2) electron-transport layer. The Fermi level of EDTA-complexed SnO2 is better matched with the conduction band of perovskite, leading to high open-circuit voltage. Its electron mobility is about three times larger than that of the SnO2. The record power conversion efficiency of planar-type PSCs with EDTA-complexed SnO2 increases to 21.60% (certified at 21.52% by Newport) with negligible hysteresis. Meanwhile, the low-temperature processed EDTA-complexed SnO2 enables 18.28% efficiency for a flexible device. Moreover, the unsealed PSCs with EDTA-complexed SnO2 degrade only by 8% exposed in an ambient atmosphere after 2880 h, and only by 14% after 120 h under irradiation at 100 mW cm−2. The development of high efficiency planar-type perovskite solar cell has been lagging behind the mesoporous-type counterpart. Here Yang et al. modify the oxide based electron transporting layer with organic acid and obtain planar-type cells with high certified efficiency of 21.5% and decent stability.
972 citations
792 citations
TL;DR: Wang et al. as discussed by the authors designed a novel type of plasmonic material, which is made by uniformly decorating fine metal nanoparticles into the 3D mesoporous matrix of natural wood.
Abstract: Plasmonic metal nanoparticles are a category of plasmonic materials that can efficiently convert light into heat under illumination, which can be applied in the field of solar steam generation. Here, this study designs a novel type of plasmonic material, which is made by uniformly decorating fine metal nanoparticles into the 3D mesoporous matrix of natural wood (plasmonic wood). The plasmonic wood exhibits high light absorption ability (≈99%) over a broad wavelength range from 200 to 2500 nm due to the plasmonic effect of metal nanoparticles and the waveguide effect of microchannels in the wood matrix. The 3D mesoporous wood with numerous low-tortuosity microchannels and nanochannels can transport water up from the bottom of the device effectively due to the capillary effect. As a result, the 3D aligned porous architecture can achieve a high solar conversion efficiency of 85% under ten-sun illumination (10 kW m−2). The plasmonic wood also exhibits superior stability for solar steam generation, without any degradation after being evaluated for 144 h. Its high conversion efficiency and excellent cycling stability demonstrate the potential of newly developed plasmonic wood to solar energy-based water desalination.
623 citations
613 citations
TL;DR: Yan et al. as mentioned in this paper used heat treatment to reduce non-radiative recombination within the heterojunction region, which is a major cause of limiting voltage output and overall performance.
Abstract: Sulfide kesterite Cu2ZnSnS4 provides an attractive low-cost, environmentally benign and stable photovoltaic material, yet the record power conversion efficiency for such solar cells has been stagnant at around 9% for years. Severe non-radiative recombination within the heterojunction region is a major cause limiting voltage output and overall performance. Here we report a certified 11% efficiency Cu2ZnSnS4 solar cell with a high 730 mV open-circuit voltage using heat treatment to reduce heterojunction recombination. This heat treatment facilitates elemental inter-diffusion, directly inducing Cd atoms to occupy Zn or Cu lattice sites, and promotes Na accumulation accompanied by local Cu deficiency within the heterojunction region. Consequently, new phases are formed near the hetero-interface and more favourable conduction band alignment is obtained, contributing to reduced non-radiative recombination. Using this approach, we also demonstrate a certified centimetre-scale (1.11 cm2) 10% efficiency Cu2ZnSnS4 photovoltaic device; the first kesterite cell (including selenium-containing) of standard centimetre-size to exceed 10%. The emerging kesterite Cu2ZnSnS4 solar cell offers a potential low-cost, non-toxic, materially abundant platform for next-generation photovoltaics, yet its efficiency has been mired below 10%. Yan et al. now use post-heat treatment of the heterojunction to show device efficiencies that surpass 10%.
586 citations
TL;DR: Correlated, in situ structural and device characterizations reveal that light-induced lattice expansion benefits the performances of a mixed-cation pure-halide planar device, boosting the power conversion efficiency from 18.5 to 20.5%.
Abstract: Light-induced structural dynamics plays a vital role in the physical properties, device performance, and stability of hybrid perovskite–based optoelectronic devices. We report that continuous light illumination leads to a uniform lattice expansion in hybrid perovskite thin films, which is critical for obtaining high-efficiency photovoltaic devices. Correlated, in situ structural and device characterizations reveal that light-induced lattice expansion benefits the performances of a mixed-cation pure-halide planar device, boosting the power conversion efficiency from 18.5 to 20.5%. The lattice expansion leads to the relaxation of local lattice strain, which lowers the energetic barriers at the perovskite-contact interfaces, thus improving the open circuit voltage and fill factor. The light-induced lattice expansion did not compromise the stability of these high-efficiency photovoltaic devices under continuous operation at full-spectrum 1-sun (100 milliwatts per square centimeter) illumination for more than 1500 hours.
522 citations
TL;DR: Using combinatory photoactive blends is a promising approach to achieve high power conversion efficiency in ternary organic photovoltaics as discussed by the authors, however, the fundamental challenge of how to manipulate th
Abstract: Using combinatory photoactive blends is a promising approach to achieve high power conversion efficiency in ternary organic photovoltaics However, the fundamental challenge of how to manipulate th
520 citations
TL;DR: Wang et al. show a controlled drying process to make phase stable and highly efficient solar cells with power conversion efficiency of 15.7%, which is the highest efficiency reported for inorganic perovskite solar cells up to now.
Abstract: Inorganic halide perovskites such as cesium lead halide are promising due to their excellent thermal stability. Cesium lead iodide (CsPbI3) has a bandgap of 1.73 eV and is very suitable for making efficient tandem solar cells, either with low-bandgap perovskite or silicon. However, the phase instability of CsPbI3 is hindering the further optimization of device performance. Here, we show that high quality and stable α-phase CsPbI3 film is obtained via solvent-controlled growth of the precursor film in a dry environment. A 15.7% power conversion efficiency of CsPbI3 solar cells is achieved, which is the highest efficiency reported for inorganic perovskite solar cells up to now. And more importantly, the devices can tolerate continuous light soaking for more than 500 h without efficiency drop.
TL;DR: In this article, the photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance, and the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management.
Abstract: Solar energy is a major source of renewable energy with the potential to meet the energy demand and to support the sustainable development of the world. The efficient harvesting and conversion of solar energy is one of the key factors to maximize the utilization of solar energy. In general, solar energy can be harnessed and converted into various kinds of energy, including electricity, fuels and thermal energy, through photovoltaic, photochemical and photothermal processes, respectively. Among these technologies, photothermal conversion is a direct conversion process that has attained the highest achievable conversion efficiency. The photothermal effect has been used as a novel strategy to augment vaporization and catalysis performance. In this review, we look into the basis of the photothermal conversion process, the design of efficient photothermal conversion materials in terms of both light harvesting and thermal management, a fundamental understanding of various system schemes, and the recent progress in photothermal evaporation and catalysis applications. This review aims to afford researchers with a better understanding of the photothermal effect and provide a guide for the rational design and development of highly efficient photothermal materials in energy and environmental fields.
01 Jun 2018
TL;DR: Luo et al. as mentioned in this paper reported a photocathode with a coaxial nanowire structure implementing a Cu2O/Ga2O3-buried p-n junction that achieves an external quantum yield for hydrogen generation close to 80%.
Abstract: Although large research efforts have been devoted to photoelectrochemical (PEC) water splitting in the past several decades, the lack of efficient, stable and Earth-abundant photoelectrodes remains a bottleneck for practical application. Here, we report a photocathode with a coaxial nanowire structure implementing a Cu2O/Ga2O3-buried p–n junction that achieves efficient light harvesting across the whole visible region to over 600 nm, reaching an external quantum yield for hydrogen generation close to 80%. With a photocurrent onset over +1 V against the reversible hydrogen electrode and a photocurrent density of ~10 mA cm−2 at 0 V versus the reversible hydrogen electrode, our electrode constitutes the best oxide photocathode for catalytic generation of hydrogen from sunlight known today. Conformal coating via atomic-layer deposition of a TiO2 protection layer enables stable operation exceeding 100 h. Using NiMo as the hydrogen evolution catalyst, an all Earth-abundant Cu2O photocathode was achieved with stable operation in a weak alkaline electrolyte. To show the practical impact of this photocathode, we constructed an all-oxide unassisted solar water splitting tandem device using state-of-the-art BiVO4 as the photoanode, achieving ~3% solar-to-hydrogen conversion efficiency. The generation of hydrogen fuel from water and visible light requires photoelectrodes that are inexpensive, stable and highly active. Now, Luo, Gratzel and co-workers report Cu2O photocathodes that reach these goals. Incorporation into an unassisted solar water splitting device gives ~3% solar-to-hydrogen conversion efficiency.
TL;DR: In this article, a method to reproduce stable and high power conversion efficiency (PCE) of a triple cation perovskite prepared using a one-step solution deposition and low-temperature annealing fully conducted in controlled ambient humidity conditions was explored.
Abstract: Perovskite solar cells have evolved to have compatible high efficiency and stability by employing mixed cation/halide type perovskite crystals as pinhole-free large grain absorbers. The cesium (Cs)–formamidium–methylammonium triple cation-based perovskite device fabricated in a glove box enables reproducible high-voltage performance. This study explores the method to reproduce stable and high power conversion efficiency (PCE) of a triple cation perovskite prepared using a one-step solution deposition and low-temperature annealing fully conducted in controlled ambient humidity conditions. Optimizing the perovskite grain size by Cs concentration and solution processes, a route is created to obtain highly uniform, pinhole-free large grain perovskite films that work with reproducible PCE up to 20.8% and high preservation stability without cell encapsulation for more than 18 weeks. This study further investigates the light intensity characteristics of open-circuit voltage (Voc) of small (5 × 5 mm2, PCE > 20%) and large (10 × 10 mm2, PCE of 18%) devices. Intensity dependence of Voc shows an ideality factor in the range of 1.7-1.9 for both devices, implying that the triple cation perovskite involves trap-assisted recombination loss at the hetero junction interfaces that influences Voc. Despite relatively high ideality factor, perovskite device is capable of supplying high power conversion efficiency under low light intensity (0.01 Sun) whereas maintaining Voc over 0.9 V.
TL;DR: A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells with high efficiency and improved stability, and upon interfacial modification with graphene quantum dots it achieved a power conversion efficiency as high as 9.72 % under standard solar illumination conditions.
Abstract: All-inorganic perovskite solar cells with high efficiency and improved stability are promising for commercialization. A multistep solution-processing method was developed to fabricate high-purity inorganic CsPbBr3 perovskite films for use in efficient solar cells. By tuning the number of deposition cycles (n) of a CsBr solution, the phase conversion from CsPb2 Br5 (n ≤3), to CsPbBr3 (n=4), and Cs4 PbBr6 (n≥5) was optimized to achieve vertical- and monolayer-aligned grains. Upon interfacial modification with graphene quantum dots, the all-inorganic perovskite solar cell (without a hole-transporting layer) achieved a power conversion efficiency (PCE) as high as 9.72 % under standard solar illumination conditions. Under challenging conditions, such as 90 % relative humidity (RH) at 25 °C or 80 °C at zero humidity, the optimized device retained 87 % PCE over 130 days or 95 % over 40 days, compared to the initial efficiency.
TL;DR: In this article, the authors characterize both external and internal photoluminescence quantum efficiency and quasi-Fermi-level splitting of surface-treated hybrid perovskite (CH3NH3PbI3) thin films.
Abstract: Reducing non-radiative recombination in semiconducting materials is a prerequisite for achieving the highest performance in light-emitting and photovoltaic applications. Here, we characterize both external and internal photoluminescence quantum efficiency and quasi-Fermi-level splitting of surface-treated hybrid perovskite (CH3NH3PbI3) thin films. With respect to the material bandgap, these passivated films exhibit the highest quasi-Fermi-level splitting measured to date, reaching 97.1 ± 0.7% of the radiative limit, approaching that of the highest performing GaAs solar cells. We confirm these values with independent measurements of internal photoluminescence quantum efficiency of 91.9 ± 2.7% under 1 Sun illumination intensity, setting a new benchmark for these materials. These results suggest hybrid perovskite solar cells are inherently capable of further increases in power conversion efficiency if surface passivation can be combined with optimized charge carrier selective interfaces. Surface treatment is shown to yield passivated perovskite films with very high quasi-Fermi level splitting and internal photoluminescence quantum efficiency, indicating that further improvements in the performance of perovskite optoelectronics should be feasible.
TL;DR: It is demonstrated that polythiophene, deposited on the top of CsPbI2 Br, can significantly reduce electron-hole recombination within the perovskite, which is due to the electronic passivation of surface defect states, and the interfacial properties are improved by a simple annealing process.
Abstract: Cesium-based trihalide perovskites have been demonstrated as promising light absorbers for photovoltaic applications due to their superb composition stability. However, the large energy losses (Eloss ) observed in inorganic perovskite solar cells has become a major hindrance impairing the ultimate efficiency. Here, an effective and reproducible method of modifying the interface between a CsPbI2 Br absorber and polythiophene hole-acceptor to minimize the Eloss is reported. It is demonstrated that polythiophene, deposited on the top of CsPbI2 Br, can significantly reduce electron-hole recombination within the perovskite, which is due to the electronic passivation of surface defect states. In addition, the interfacial properties are improved by a simple annealing process, leading to significantly reduced energy disorder in polythiophene and enhanced hole-injection into the hole-acceptor. Consequently, one of the highest power conversion efficiency (PCE) of 12.02% from a reverse scan in inorganic mixed-halide perovskite solar cells is obtained. Modifying the perovskite films with annealing polythiophene enables an open-circuit voltage (VOC ) of up to 1.32 V and Eloss of down to 0.5 eV, which both are the optimal values reported among cesium-lead mixed-halide perovskite solar cells to date. This method provides a new route to further improve the efficiency of perovskite solar cells by minimizing the Eloss .
TL;DR: In this article, the authors focus on the recent developments in water splitting techniques using photoelectrochemical (PEC) based nanomaterials as well as different strategies to improve hydrogen evolution.
TL;DR: In this work, a new nonfullerene acceptor of DF-PCIC is synthesized with an unfused-ring core containing two cyclopentadithiophene moieties and one 2,5-difluorobenzene (DFB) group, providing new idea for the design of new non fullereneacceptors applicable in commercial OSCs in the future.
Abstract: Most nonfullerene acceptors developed so far for high-performance organic solar cells (OSCs) are designed in planar molecular geometry containing a fused-ring core. In this work, a new nonfullerene acceptor of DF-PCIC is synthesized with an unfused-ring core containing two cyclopentadithiophene (CPDT) moieties and one 2,5-difluorobenzene (DFB) group. A nearly planar geometry is realized through the F···H noncovalent interaction between CPDT and DFB for DF-PCIC. After proper optimizations, the OSCs with DF-PCIC as the acceptor and the polymer PBDB-T as the donor yield the best power conversion efficiency (PCE) of 10.14% with a high fill factor of 0.72. To the best of our knowledge, this efficiency is among the highest values for the OSCs with nonfullerene acceptors owning unfused-ring cores. Furthermore, no obvious morphological changes are observed for the thermally treated PBDB-T:DF-PCIC blended films, and the relevant devices can keep ≈70% of the original PCEs upon thermal treatment at 180 °C for 12 h. This tolerance of such a high temperature for so long time is rarely reported for fullerene-free OSCs, which might be due to the unique unfused-ring core of DF-PCIC. Therefore, the work provides new idea for the design of new nonfullerene acceptors applicable in commercial OSCs in the future.
TL;DR: Two cheliform non-fullerene acceptors, DTPC-IC andDTPC-DFIC, based on a highly electron-rich core, dithienopicenocarbazole (DTPC), are synthesized, showing ultra-narrow bandgaps and strong electron-donating capability.
Abstract: Two cheliform non-fullerene acceptors, DTPC-IC and DTPC-DFIC, based on a highly electron-rich core, dithienopicenocarbazole (DTPC), are synthesized, showing ultra-narrow bandgaps (as low as 1.21 eV). The two-dimensional nitrogen-containing conjugated DTPC possesses strong electron-donating capability, which induces intense intramolecular charge transfer and intermolecular π–π stacking in derived acceptors. The solar cell based on DTPC-DFIC and a spectrally complementary polymer donor, PTB7-Th, showed a high power conversion efficiency of 10.21% and an extremely low energy loss of 0.45 eV, which is the lowest among reported efficient OSCs.
TL;DR: In this work, a SnO2 /ZnO bilayered electron transporting layer (ETL) aimed to achieve low energy loss and large open-circuit voltage (Voc) for high-efficiency all-inorganic CsPbI2 Br perovskite solar cells (PVSCs) is introduced.
Abstract: In this work, a SnO2 /ZnO bilayered electron transporting layer (ETL) aimed to achieve low energy loss and large open-circuit voltage (Voc ) for high-efficiency all-inorganic CsPbI2 Br perovskite solar cells (PVSCs) is introduced. The high-quality CsPbI2 Br film with regular crystal grains and full coverage can be realized on the SnO2 /ZnO surface. The higher-lying conduction band minimum of ZnO facilitates desirable cascade energy level alignment between the perovskite and SnO2 /ZnO bilayered ETL with superior electron extraction capability, resulting in a suppressed interfacial trap-assisted recombination with lower charge recombination rate and greater charge extraction efficiency. The as-optimized all-inorganic PVSC delivers a high Voc of 1.23 V and power conversion efficiency (PCE) of 14.6%, which is one of the best efficiencies reported for the Cs-based all-inorganic PVSCs to date. More importantly, decent thermal stability with only 20% PCE loss is demonstrated for the SnO2 /ZnO-based CsPbI2 Br PVSCs after being heated at 85 °C for 300 h. These findings provide important interface design insights that will be crucial to further improve the efficiency of all-inorganic PVSCs in the future.
TL;DR: The physics of band alignment, the chemistry of surface modification and the behavior of photoexcited charge transfer at the interface during PV and PEC processes will be discussed and possible strategies to improve their performance are discussed.
Abstract: Graphene and two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant interest due to their unique properties that cannot be obtained in their bulk counterparts. These atomically thin 2D materials have demonstrated strong light–matter interactions, tunable optical bandgap structures and unique structural and electrical properties, rendering possible the high conversion efficiency of solar energy with a minimal amount of active absorber material. The isolated 2D monolayer can be stacked into arbitrary van der Waals (vdWs) heterostructures without the need to consider lattice matching. Several combinations of 2D/3D and 2D/2D materials have been assembled to create vdWs heterojunctions for photovoltaic (PV) and photoelectrochemical (PEC) energy conversion. However, the complex, less-constrained, and more environmentally vulnerable interface in a vdWs heterojunction is different from that of a conventional, epitaxially grown heterojunction, engendering new challenges for surface and interface engineering. In this review, the physics of band alignment, the chemistry of surface modification and the behavior of photoexcited charge transfer at the interface during PV and PEC processes will be discussed. We will present a survey of the recent progress and challenges of 2D/3D and 2D/2D vdWs heterojunctions, with emphasis on their applicability to PV and PEC devices. Finally, we will discuss emerging issues yet to be explored for 2D materials to achieve high solar energy conversion efficiency and possible strategies to improve their performance.
TL;DR: Bi12 O17 Cl2 superfine nanotubes with a bilayer thickness of the tube wall are designed to achieve structural distortion for the creation of surface oxygen defects, thus accelerating the carrier migration and facilitating CO2 activation.
Abstract: Solar-driven reduction of CO2 , which converts inexhaustible solar energy into value-added fuels, has been recognized as a promising sustainable energy conversion technology However, the overall conversion efficiency is significantly limited by the inefficient charge separation and sluggish interfacial reaction dynamics, which resulted from a lack of sufficient active sites Herein, Bi12 O17 Cl2 superfine nanotubes with a bilayer thickness of the tube wall are designed to achieve structural distortion for the creation of surface oxygen defects, thus accelerating the carrier migration and facilitating CO2 activation Without cocatalyst and sacrificing reagent, Bi12 O17 Cl2 nanotubes deliver high selectivity CO evolution rate of 486 μmol g-1 h-1 in water (168 times than of bulk Bi12 O17 Cl2 ), while maintaining stability even after 12 h of testing This paves the way to design efficient photocatalysts with collaborative optimizing charge separation and CO2 activation towards CO2 photoreduction
TL;DR: In this paper, a CsPbI2+xBr1−x perovskite solar cell with a graded bandgap was explored using CpbBrI2 and CpBI3 quantum dots as component cells.
TL;DR: This work demonstrates that the newly developed sulfur and nitrogen codoped NIR CDs are highly efficient in photothermal therapy (PTT) in mouse models (conversion efficiency of 59%) and can be readily visualized by photoluminescence and photoacoustic imaging.
Abstract: Carbon dots that exhibit near-infrared fluorescence (NIR CDs) are considered emerging nanomaterials for advanced biomedical applications with low toxicity and superior photostability and targeting compared to currently used photoluminescence agents. Despite progress in the synthesis of NIR CDs, there remains a key obstacle to using them as an in vivo theranostic agent. This work demonstrates that the newly developed sulfur and nitrogen codoped NIR CDs are highly efficient in photothermal therapy (PTT) in mouse models (conversion efficiency of 59%) and can be readily visualized by photoluminescence and photoacoustic imaging. The real theranostic potential of NIR CDs is enhanced by their unique biodistribution and targeting. Contrary to all other nanomaterials that have been tested in biomedicine, they are excreted through the body’s renal filtration system. Moreover, after intravenous injection, NIR CDs are accumulated in tumor tissue via passive targeting, without any active species such as antibodies. Due to their accumulation in tumor tissue without the need for intratumor injection, high photothermal conversion, excellent optical and photoacoustic imaging performance, and renal excretion, the developed CDs are suitable for transfer to clinical biomedical practice. ‘Carbon dot’ nanoparticles composed largely of carbon, but doped with sulfur and nitrogen, accumulate within cancer cells and absorb near-infrared laser light to generate cell-killing heat. The procedure was developed and tested by researchers in China and the Czech Republic, led by Songnan Qu at the Changchung Institute of Optics, Fine Mechanics and Physics. The nanoparticles accumulated passively in tumors after intravenous injection into mice, with no specific targeting methods required. Tumors were effectively eradicated by the highly efficient conversion of the light energy into heat. The nanoparticles are biocompatible and are eventually excreted harmlessly in urine. In addition to the potential for treating cancer, diagnosis can also be assisted using the particles’ fluorescent properties. This combination of therapy and diagnosis – ‘theranostics’ – can now be further developed and explored for use in patients.
TL;DR: In this paper, an advanced dye-sensitized solar cells (DSCs) architecture is presented, which achieves efficiencies of 13.1% under air mass 1.5 global, 100 mW cm −2 solar radiation, and power conversion efficiency of 32% under a standard Osram 930 Warm White fluorescent tube light at 1,000 lux intensity.
TL;DR: Dye R6 displays a brilliant sapphire color in a sensitized TiO2 mesoporous film with a Co(II/III) tris(bipyridyl)-based redox electrolyte and achieves an impressive power conversion efficiency and shows a remarkable photostability.
Abstract: We report a blue dye, coded as R6, which features a polycyclic aromatic hydrocarbon, 9,19-dihydrobenzo[1′,10′]phenanthro[3′,4′:4,5]thieno[3,2-b]benzo[1,10]phenanthro[3,4-d]thiophene, coupled with a diarylamine electron donor and 4-(7-ethynylbenzo[c][1,2,5]thiadiazol-4-yl)benzoic acid acceptor. Dye R6 displays a brilliant sapphire color in a sensitized TiO2 mesoporous film with a Co(II/III) tris(bipyridyl)-based redox electrolyte. The R6 based dye-sensitized solar cell achieves an impressive power conversion efficiency of 12.6% under standard air mass 1.5 global, 100 mW cm–2, and shows a remarkable photostability.
TL;DR: Efficient and water-stable quasi-2D perovskite solar cells with a peak PCE of 18.20% by using 3-bromobenzylammonium iodide are demonstrated and can work well as light-emitting diodes (LEDs), exhibiting an external quantum efficiency of 3.85% and a long operational lifetime of ≈96 h at a high current density in air.
Abstract: Quasi-2D layered organometal halide perovskites have recently emerged as promising candidates for solar cells, because of their intrinsic stability compared to 3D analogs. However, relatively low power conversion efficiency (PCE) limits the application of 2D layered perovskites in photovoltaics, due to large energy band gap, high exciton binding energy, and poor interlayer charge transport. Here, efficient and water-stable quasi-2D perovskite solar cells with a peak PCE of 18.20% by using 3-bromobenzylammonium iodide are demonstrated. The unencapsulated devices sustain over 82% of their initial efficiency after 2400 h under relative humidity of ≈40%, and show almost unchanged photovoltaic parameters after immersion into water for 60 s. The robust performance of perovskite solar cells results from the quasi-2D perovskite films with hydrophobic nature and a high degree of electronic order and high crystallinity, which consists of both ordered large-bandgap perovskites with the vertical growth in the bottom region and oriented small-bandgap components in the top region. Moreover, due to the suppressed nonradiative recombination, the unencapsulated photovoltaic devices can work well as light-emitting diodes (LEDs), exhibiting an external quantum efficiency of 3.85% and a long operational lifetime of ≈96 h at a high current density of 200 mA cm-2 in air.
TL;DR: An inorganic-perovskite/organic four-terminal tandem solar cell based on a semitransparent inorganic CsPbBr3 perovskITE solar cell (pero-SC) as the top cell and an OSC as bottom cell is constructed, avoiding the instability problem of UV light on the bottom OSC and leading to the highest reported PCE.
Abstract: Organic solar cells (OSCs) can be unstable under ultraviolet (UV) irradiation. To address this issue and enhance the power conversion efficiency (PCE), an inorganic-perovskite/organic four-terminal tandem solar cell (TSC) based on a semitransparent inorganic CsPbBr3 perovskite solar cell (pero-SC) as the top cell and an OSC as bottom cell is constructed. The high-quality CsPbBr3 photoactive layer of the planar pero-SC is prepared with a dual-source vacuum coevaporation method, using stoichiometric precursors of CsBr and PbBr2 with a low evaporation rate. The resultant opaque planar pero-SC exhibits an ultrahigh open-circuit voltage of 1.44 V and the highest reported PCE of 7.78% for a CsPbBr3 -based planar pero-SC. Importantly, the devices show no degradation after 120 h UV light illumination. The related semitransparent pero-SC can almost completely filter UV light and well maintain photovoltaic performance; it additionally shows an extremely high average visible transmittance. When it is used to construct a TSC, the top pero-SC acting as a UV filter can utilize UV light for photoelectric conversion, avoiding the instability problem of UV light on the bottom OSC that can meet the industrial standards of UV-light stability for solar cells, and leading to the highest reported PCE of 14.03% for the inorganic-perovskite/organic TSC.