Metal Oxides as Efficient Charge Transporters in Perovskite Solar Cells
TL;DR: In this paper, a comprehensive review on the synthesis and applications of metal oxides as electron and hole transporters in efficient perovskite solar cells with both mesoporous and planar architectures is presented.
Abstract: Over the past few years, hybrid halide perovskites have emerged as a highly promising class of materials for photovoltaic technology, and the power conversion efficiency of perovskite solar cells (PSCs) has accelerated at an unprecedented pace, reaching a record value of over 22%. In the context of PSC research, wide-bandgap semiconducting metal oxides have been extensively studied because of their exceptional performance for injection and extraction of photo-generated carriers. In this comprehensive review, we focus on the synthesis and applications of metal oxides as electron and hole transporters in efficient PSCs with both mesoporous and planar architectures. Metal oxides and their doped variants with proper energy band alignment with halide perovskites, in the form of nanostructured layers and compact thin films, can not only assist with charge transport but also improve the stability of PSCs under ambient conditions. Strategies for the implementation of metal oxides with tailored compositions and structures, and for the engineering of their interfaces with perovskites will be critical for the future development and commercialization of PSCs.
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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 .
388 citations
TL;DR: A unique outlook on the paths toward commercialization of PVKSCs from the interfacial engineering perspective is offered, relevant to both specialists and nonspecialists in the field through a brief introduction of the background of the field, current state-of-the-art evolution, and future research prospects.
Abstract: High-efficiency and low-cost perovskite solar cells (PVKSCs) are an ideal candidate for addressing the scalability challenge of solar-based renewable energy. The dynamically evolving research field of PVKSCs has made immense progress in solving inherent challenges and capitalizing on their unique structure-property-processing-performance traits. This review offers a unique outlook on the paths toward commercialization of PVKSCs from the interfacial engineering perspective, relevant to both specialists and nonspecialists in the field through a brief introduction of the background of the field, current state-of-the-art evolution, and future research prospects. The multifaceted role of interfaces in facilitating PVKSC development is explained. Beneficial impacts of diverse charge-transporting materials and interfacial modifications are summarized. In addition, the role of interfaces in improving efficiency and stability for all emerging areas of PVKSC design are also evaluated. The authors' integral contributions in this area are highlighted on all fronts. Finally, future research opportunities for interfacial material development and applications along with scalability-durability-sustainability considerations pivotal for facilitating laboratory to industry translation are presented.
301 citations
TL;DR: Two novel donor-acceptor-type SM-HTMs (MPA-BTI and MPA-BTTI) are devised, which synergistically integrate several design principles for high-performance HTMs, and exhibit comparable optoelectronic properties but distinct molecular configuration and film properties, enabling a remarkable efficiency of 21.17% in inverted PVSCs.
Abstract: Hole-transporting materials (HTMs) play a critical role in realizing efficient and stable perovskite solar cells (PVSCs). Considering their capability of enabling PVSCs with good device reproducibility and long-term stability, high-performance dopant-free small-molecule HTMs (SM-HTMs) are greatly desired. However, such dopant-free SM-HTMs are highly elusive, limiting the current record efficiencies of inverted PVSCs to around 19%. Here, two novel donor-acceptor-type SM-HTMs (MPA-BTI and MPA-BTTI) are devised, which synergistically integrate several design principles for high-performance HTMs, and exhibit comparable optoelectronic properties but distinct molecular configuration and film properties. Consequently, the dopant-free MPA-BTTI-based inverted PVSCs achieve a remarkable efficiency of 21.17% with negligible hysteresis and superior thermal stability and long-term stability under illumination, which breaks the long-time standing bottleneck in the development of dopant-free SM-HTMs for highly efficient inverted PVSCs. Such a breakthrough is attributed to the well-aligned energy levels, appropriate hole mobility, and most importantly, the excellent film morphology of the MPA-BTTI. The results underscore the effectiveness of the design tactics, providing a new avenue for developing high-performance dopant-free SM-HTMs in PVSCs.
246 citations
TL;DR: In this article, the authors outline similarities and differences between polycrystalline thin-film photovoltaic materials from both the materials and the industrial point of view and address the materials characteristics and device concepts for each technology, including a description of recent developments that have led to very high efficiency achievements.
Abstract: Already, several technologies of polycrystalline thin‐film photovoltaic materials have achieved certified record small‐cell power conversion efficiencies exceeding 22%. They are CdTe, Cu(In,Ga)(S,Se)2 (CIGS), and metal halide perovskite (PSC), each named after the light-absorbing semiconductor material. Thin-film solar cells and modules require very little active material due to their very high absorption coefficient. Efficient production methods with low materials waste, moderate temperatures, attractive cost structures, and favorable energy payback times will play a strong role in market development as thin-film technologies reach full maturity, including mass production and the standardization of production machineries. In fact, the first two technologies have already been developed up to the industrial scale with a market share of several GW. In this review article, we outline similarities and differences between these high‐efficiency thin‐film technologies from both the materials and the industrial point of view. We address the materials characteristics and device concepts for each technology, including a description of recent developments that have led to very high efficiency achievements. We provide an overview of the CIGS industry players and their current status. The newcomer PSC has demonstrated its potential in the laboratory, and initial efforts in industrial production are underway. A large number of laboratories are experimenting through a wide range of options in order to optimize not only the efficiency but also stability, environmental aspects, and manufacturability of PSC. Its high efficiency and its high bandgap make PSC particularly attractive for tandem applications. An overview of all these topics is included here along with a list of materials configurations.
157 citations
01 May 2019
TL;DR: In this article, a comprehensive review summarizes the recent progress in the fabrication of NiOx films and their application in organometallic halide perovskite solar cells (PSCs).
Abstract: Organic–inorganic halide perovskite solar cells (PSCs) have achieved great success in recent years with a demonstrated power conversion efficiency (PCE) increasing rapidly from 3.8% to 22.3% for single junction devices. Most high-performance PSCs consist of a perovskite absorber sandwiched between an electron transport layer (ETL) and a hole transport layer (HTL), which extracts electrons (holes) and blocks holes (electrons) from the absorber efficiently. Inorganic hole transport materials have extracted extensive attention due to their higher mobility and better stability. Particularly, the excellent hole selective transport property of nickel oxide (NiOx) has been highlighted by its recent application in organometallic halide PSCs, due to the favorable band alignment formed between the halide perovskite absorber and NiOx HTL. This comprehensive review summarizes the recent progress in the fabrication of NiOx films and their application in PSCs. Special attention is paid to the optoelectronic properties of NiOx films, which strongly depend on the synthesis methods and post-treatment conditions, as well as the resulting photovoltaic device performance. Surface modification and doping strategies that are used to improve the optoelectronic properties of NiOx films and the resulting device performance are discussed with emphasis. Finally, a short perspective of NiOx-based PSCs is also provided.
140 citations
References
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TL;DR: In this article, the authors describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency.
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
26,457 citations
TL;DR: Two organolead halide perovskite nanocrystals were found to efficiently sensitize TiO(2) for visible-light conversion in photoelectrochemical cells, which exhibit strong band-gap absorptions as semiconductors.
Abstract: Two organolead halide perovskite nanocrystals, CH3NH3PbBr3 and CH3NH3PbI3, were found to efficiently sensitize TiO2 for visible-light conversion in photoelectrochemical cells. When self-assembled on mesoporous TiO2 films, the nanocrystalline perovskites exhibit strong band-gap absorptions as semiconductors. The CH3NH3PbI3-based photocell with spectral sensitivity of up to 800 nm yielded a solar energy conversion efficiency of 3.8%. The CH3NH3PbBr3-based cell showed a high photovoltage of 0.96 V with an external quantum conversion efficiency of 65%.
16,634 citations
TL;DR: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature.
Abstract: The semiconductor ZnO has gained substantial interest in the research community in part because of its large exciton binding energy (60meV) which could lead to lasing action based on exciton recombination even above room temperature. Even though research focusing on ZnO goes back many decades, the renewed interest is fueled by availability of high-quality substrates and reports of p-type conduction and ferromagnetic behavior when doped with transitions metals, both of which remain controversial. It is this renewed interest in ZnO which forms the basis of this review. As mentioned already, ZnO is not new to the semiconductor field, with studies of its lattice parameter dating back to 1935 by Bunn [Proc. Phys. Soc. London 47, 836 (1935)], studies of its vibrational properties with Raman scattering in 1966 by Damen et al. [Phys. Rev. 142, 570 (1966)], detailed optical studies in 1954 by Mollwo [Z. Angew. Phys. 6, 257 (1954)], and its growth by chemical-vapor transport in 1970 by Galli and Coker [Appl. Phys. ...
10,260 citations
TL;DR: In this paper, the carrier collection efficiency and energy conversion efficiency of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives.
Abstract: The carrier collection efficiency (ηc) and energy conversion efficiency (ηe) of polymer photovoltaic cells were improved by blending of the semiconducting polymer with C60 or its functionalized derivatives. Composite films of poly(2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) and fullerenes exhibit ηc of about 29 percent of electrons per photon and ηe of about 2.9 percent, efficiencies that are better by more than two orders of magnitude than those that have been achieved with devices made with pure MEH-PPV. The efficient charge separation results from photoinduced electron transfer from the MEH-PPV (as donor) to C60 (as acceptor); the high collection efficiency results from a bicontinuous network of internal donor-acceptor heterojunctions.
9,611 citations
9,432 citations