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Showing papers by "Michael Grätzel published in 2016"


Journal ArticleDOI
TL;DR: In this paper, the triple cation perovskite photovoltaics with inorganic cesium were shown to be thermally more stable, contain less phase impurities and are less sensitive to processing conditions.
Abstract: Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and ∼18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.

3,470 citations


Journal ArticleDOI
14 Oct 2016-Science
TL;DR: This work shows that the small and oxidation-stable rubidium cation (Rb+) can be embedded into a “cation cascade” to create perovskite materials with excellent material properties and achieved stabilized efficiencies of up to 21.6% on small areas.
Abstract: All of the cations currently used in perovskite solar cells abide by the tolerance factor for incorporation into the lattice. We show that the small and oxidation-stable rubidium cation (Rb + ) can be embedded into a “cation cascade” to create perovskite materials with excellent material properties. We achieved stabilized efficiencies of up to 21.6% (average value, 20.2%) on small areas (and a stabilized 19.0% on a cell 0.5 square centimeters in area) as well as an electroluminescence of 3.8%. The open-circuit voltage of 1.24 volts at a band gap of 1.63 electron volts leads to a loss in potential of 0.39 volts, versus 0.4 volts for commercial silicon cells. Polymer-coated cells maintained 95% of their initial performance at 85°C for 500 hours under full illumination and maximum power point tracking.

3,034 citations


Journal ArticleDOI
TL;DR: A new metal halide perovskite photovoltaic cell that exhibits both very high solar-to-electric power-conversion efficiency and intense electroluminescence is reported on.
Abstract: We report on a new metal halide perovskite photovoltaic cell that exhibits both very high solar-to-electric power-conversion efficiency and intense electroluminescence. We produce the perovskite films in a single step from a solution containing a mixture of FAI, PbI2, MABr, and PbBr2 (where FA stands for formamidinium cations and MA stands for methylammonium cations). Using mesoporous TiO2 and Spiro-OMeTAD as electron- and hole-specific contacts, respectively, we fabricate perovskite solar cells that achieve a maximum power-conversion efficiency of 20.8% for a PbI2/FAI molar ratio of 1.05 in the precursor solution. Rietveld analysis of x-ray diffraction data reveals that the excess PbI2 content incorporated into such a film is about 3 weight percent. Time-resolved photoluminescence decay measurements show that the small excess of PbI2 suppresses nonradiative charge carrier recombination. This in turn augments the external electroluminescence quantum efficiency to values of about 0.5%, a record for perovskite photovoltaics approaching that of the best silicon solar cells. Correspondingly, the open-circuit photovoltage reaches 1.18 V under AM 1.5 sunlight.

1,659 citations


Journal ArticleDOI
TL;DR: In this article, an approach to prepare perovskite films of high electronic quality by using poly(methyl methacrylate) (PMMA) as a template to control nucleation and crystal growth is presented.
Abstract: The past several years have witnessed the rapid emergence of a class of solar cells based on mixed organic–inorganic halide perovskites. Today’s state-of-the-art perovskite solar cells (PSCs) employ various methods to enhance nucleation and improve the smoothness of the perovskite films formed via solution processing. However, the lack of precise control over the crystallization process creates a risk of forming unwanted defects, for example, pinholes and grain boundaries. Here, we introduce an approach to prepare perovskite films of high electronic quality by using poly(methyl methacrylate) (PMMA) as a template to control nucleation and crystal growth. We obtain shiny smooth perovskite films of excellent electronic quality, as manifested by a remarkably long photoluminescence lifetime. We realize stable PSCs with excellent reproducibility showing a power conversion efficiency (PCE) of up to 21.6% and a certified PCE of 21.02% under standard AM 1.5G reporting conditions. Controlling the crystallization process of perovskite films is crucial to obtaining high efficiency in perovskite solar cells. Bi et al. propose the use of poly(methyl methacrylate) as a template for the controlled nucleation and growth of perovskite crystals achieving efficiency of 21.6%.

1,626 citations


Journal ArticleDOI
01 Jul 2016-Science
TL;DR: A simple vacuum flash–assisted solution processing method is devised to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas, which enables the realization of highly efficient large-area PSCs for practical deployment.
Abstract: Metal halide perovskite solar cells (PSCs) currently attract enormous research interest because of their high solar-to-electric power conversion efficiency (PCE) and low fabrication costs, but their practical development is hampered by difficulties in achieving high performance with large-size devices. We devised a simple vacuum flash-assisted solution processing method to obtain shiny, smooth, crystalline perovskite films of high electronic quality over large areas. This enabled us to fabricate solar cells with an aperture area exceeding 1 square centimeter, a maximum efficiency of 20.5%, and a certified PCE of 19.6%. By contrast, the best certified PCE to date is 15.6% for PSCs of similar size. We demonstrate that the reproducibility of the method is excellent and that the cells show virtually no hysteresis. Our approach enables the realization of highly efficient large-area PSCs for practical deployment.

1,586 citations


Journal ArticleDOI
TL;DR: In this paper, the optoelectronic properties of mixed A-cation perovskites and the underlying reasons for their excellent performance and high stability were analyzed using first principle computations.
Abstract: ABX3-type organic lead halide perovskites currently attract broad attention as light harvesters for solar cells due to their high power conversion efficiency (PCE). Mixtures of formamidinium (FA) with methylammonium (MA) as A-cations show currently the best performance. Apart from offering better solar light harvesting in the near IR the addition of methylammonium stabilizes the perovskite phase of FAPbI3 which in pure form at room temperature converts to the yellow photovoltaically inactive δ-phase. We observe a similar phenomenon upon adding Cs+ cations to FAPbI3. CsPbI3 and FAPbI3 both form the undesirable yellow phase under ambient condition while the mixture forms the desired black pervoskite. Solar cells employing the composition Cs0.2FA0.8PbI2.84Br0.16 yield high average PCEs of over 17% exhibiting negligible hysteresis and excellent long term stability in ambient air. We elucidate here this remarkable behavior using first principle computations. These show that the remarkable stabilization of the perovskite phase by mixing the A-cations stems from entropic gains and the small internal energy input required for the formation of their solid solution. By contrast, the energy of formation of the delta-phase containing mixed cations is too large to be compensated by this configurational entropy increase. Our calculations reveal for the first time the optoelectronic properties of such mixed A-cation perovskites and the underlying reasons for their excellent performance and high stability.

1,032 citations


Journal ArticleDOI
TL;DR: Park et al. as discussed by the authors proposed a reproducible manufacturing method for perovskite solar cells, as well as routes to manage grain boundaries and interfacial charge transport to achieve long-term stability.
Abstract: Solar cells employing a halide perovskite with an organic cation now show power conversion efficiency of up to 22%. However, these cells are facing issues towards commercialization, such as the need to achieve long-term stability and the development of a manufacturing method for the reproducible fabrication of high-performance devices. Here, we propose a strategy to obtain stable and commercially viable perovskite solar cells. A reproducible manufacturing method is suggested, as well as routes to manage grain boundaries and interfacial charge transport. Electroluminescence is regarded as a metric to gauge theoretical efficiency. We highlight how optimizing the design of device architectures is important not only for achieving high efficiency but also for hysteresis-free and stable performance. We argue that reliable device characterization is needed to ensure the advance of this technology towards practical applications. We believe that perovskite-based devices can be competitive with silicon solar modules, and discuss issues related to the safe management of toxic material. Perovskite solar cells have emerged as a potential low-cost alternative to existing technologies. In this Perspective, Park et al. explore a strategy for the commercialisation of perovskite solar cells.

920 citations


Journal ArticleDOI
20 May 2016-ACS Nano
TL;DR: It is found that exposing PSCs to a temperature of 70 °C is enough to induce gold migration through the hole-transporting layer (HTL), spiro-MeOTAD, and into the perovskite material, which in turn severely affects the device performance metrics under working conditions.
Abstract: Perovskite solar cells (PSCs) have now achieved efficiencies in excess of 22%, but very little is known about their long-term stability under thermal stress. So far, stability reports have hinted at the importance of substituting the organic components, but little attention has been given to the metal contact. We investigated the stability of state-of-the-art PSCs with efficiencies exceeding 20%. Remarkably, we found that exposing PSCs to a temperature of 70 °C is enough to induce gold migration through the hole-transporting layer (HTL), spiro-MeOTAD, and into the perovskite material, which in turn severely affects the device performance metrics under working conditions. Importantly, we found that the main cause of irreversible degradation is not due to decomposition of the organic and hybrid perovskite layers. By introducing a Cr metal interlayer between the HTL and gold electrode, high-temperature-induced irreversible long-term losses are avoided. This key finding is essential in the quest for achieving...

914 citations


Journal ArticleDOI
TL;DR: An overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials.
Abstract: The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials.

733 citations


Journal ArticleDOI
14 Oct 2016-Science
TL;DR: It is shown that rapid light–induced free-radical polymerization at ambient temperature produces multifunctional fluorinated photopolymer coatings that confer luminescent and easy-cleaning features on the front side of the devices, while concurrently forming a strongly hydrophobic barrier toward environmental moisture on the back contact side.
Abstract: Organometal halide perovskite solar cells have demonstrated high conversion efficiency but poor long-term stability against ultraviolet irradiation and water. We show that rapid light-induced free-radical polymerization at ambient temperature produces multifunctional fluorinated photopolymer coatings that confer luminescent and easy-cleaning features on the front side of the devices, while concurrently forming a strongly hydrophobic barrier toward environmental moisture on the back contact side. The luminescent photopolymers re-emit ultraviolet light in the visible range, boosting perovskite solar cells efficiency to nearly 19% under standard illumination. Coated devices reproducibly retain their full functional performance during prolonged operation, even after a series of severe aging tests carried out for more than 6 months.

716 citations


Journal ArticleDOI
TL;DR: In this paper, a simple solution-processed technological approach for depositing SnO2 layers in planar PSCs yields a high stabilized power conversion efficiency close to 21%, exhibiting stable performance under real operating conditions for over 60 hours.
Abstract: Perovskite solar cells (PSCs) are one of the most promising lab-scale technologies to deliver inexpensive solar electricity. Low-temperature planar PSCs are particularly suited for large-scale manufacturing. Here, we propose a simple, solution-processed technological approach for depositing SnO2 layers. The use of these layers in planar PSCs yields a high stabilized power conversion efficiency close to 21%, exhibiting stable performance under real operating conditions for over 60 hours. In addition, this method yielded remarkable voltages of 1214 mV at a band gap of 1.62 eV (approaching the thermodynamic limit of 1.32 V) confirming the high selectivity of the solution-processed layers. PSCs aged under 1 sun illumination and maximum power point tracking showed a final PCE of 20.7% after ageing and dark storage, which is slightly higher than the original efficiency. This approach represents an advancement in the understanding of the role of electron selective layers on the efficiency and stability of PSCs. Therefore, the newly proposed approach constitutes a simple, scalable method paving the way for industrialization of perovskite solar cells.

Journal ArticleDOI
TL;DR: In this article, the authors explored the perovskites in a compositional space and derived the absorption and the emission behavior as well as the crystallographic properties of the pervskites.
Abstract: Lead halide perovskites have attracted considerable interest as photoabsorbers in PV-applications over the last few years. The most studied perovskite material achieving high photovoltaic performance has been methyl ammonium lead iodide, CH3NH3PbI3. Recently the highest solar cell efficiencies have, however, been achieved with mixed perovskites where iodide and methyl ammonium partially have been replaced by bromide and formamidinium. In this work, the mixed perovskites were explored in a systematic way by manufacturing devices where both iodide and methyl ammonium were gradually replaced by bromide and formamidinium. The absorption and the emission behavior as well as the crystallographic properties were explored for the perovskites in this compositional space. The band gaps as well as the crystallographic structures were extracted. Small changes in the composition of the perovskite were found to have a large impact on the properties of the materials and the device performance. In the investigated compositional space, cell efficiencies, for example, vary from a few percent up to 20.7%. From the perspective of applications, exchanging iodide with bromide is especially interesting as it allows tuning of the band gap from 1.5 to 2.3 eV. This is highly beneficial for tandem applications, and an empirical expression for the band gap as a function of composition was determined. Exchanging a small amount of iodide with bromide is found to be highly beneficial, whereas a larger amount of bromide in the perovskite was found to cause intense sub band gap photoemission with detrimental results for the device performance. This could be caused by the formation of a small amount of an iodide rich phase with a lower band gap, even though such a phase was not observed in diffraction experiments. This shows that stabilizing the mixed perovskites will be an important task in order to get the bromide rich perovskites, which has a higher band gap, to reach the same high performance obtained with the best compositions.

Journal ArticleDOI
TL;DR: In this paper, an 18% efficient monolithic silicon/perovskite tandem solar cells were constructed by combining optical optimization of the device architecture including light trapping approaches. But the design of the tandem cell is limited by the photocurrent generated in the silicon bottom cell that is reduced due to reflectance losses.
Abstract: Tandem solar cells combining silicon and perovskite absorbers have the potential to outperform state-of-the-art high efficiency silicon single junction devices. However, the practical fabrication of monolithic silicon/perovskite tandem solar cells is challenging as material properties and processing requirements such as temperature restrict the device design. Here, we fabricate an 18% efficient monolithic tandem cell formed by a silicon heterojunction bottom- and a perovskite top-cell enabling a very high open circuit voltage of 1.78 V. The monolithic integration was realized via low temperature processing of the semitransparent perovskite sub-cell where an energetically aligned electron selective contact was fabricated by atomic layer deposition of tin oxide. The hole selective, transparent top contact was formed by a stack of the organic hole transport material spiro-OMeTAD, molybdenum oxide and sputtered indium tin oxide. The tandem cell design is currently limited by the photocurrent generated in the silicon bottom cell that is reduced due to reflectance losses. Based on optical modelling and first experiments, we show that these losses can be significantly reduced by combining optical optimization of the device architecture including light trapping approaches.

Journal ArticleDOI
TL;DR: A new synthetic method to grow Cu2O nanowire arrays on conductive fluorine-doped tin oxide substrates with well-controlled phase and excellent electronic and photonic properties is developed and an innovative blocking layer strategy is introduced to enable high performance.
Abstract: Due to its abundance, scalability, and nontoxicity, Cu2O has attracted extensive attention toward solar energy conversion, and it is the best performing metal oxide material. Until now, the high efficiency devices are all planar in structure, and their photocurrent densities still fall well below the theoretical value of 14.5 mA cm(-2) due to the incompatible light absorption and charge carrier diffusion lengths. Nanowire structures have been considered as a rational and promising approach to solve this issue, but due to various challenges, performance improvements through the use of nanowires have rarely been achieved. In this work, we develop a new synthetic method to grow Cu2O nanowire arrays on conductive fluorine-doped tin oxide substrates with well-controlled phase and excellent electronic and photonic properties. Also, we introduce an innovative blocking layer strategy to enable high performance. Further, through material engineering by combining a conformal nanoscale p-n junction, durable protective overlayer, and uniform catalyst decoration, we have successfully fabricated Cu2O nanowire array photocathodes for hydrogen generation from solar water splitting delivering unprecedentedly high photocurrent densities of 10 mA cm(-2) and stable operation beyond 50 h, establishing a new benchmark for metal oxide based photoelectrodes.

Journal ArticleDOI
TL;DR: The synthesis of two-dimensional (2D) Cu-based hybrid perovskites is presented and their optoelectronic properties studied to investigate their potential application in solar cells and light-emitting devices, providing a new environmental-friendly alternative to Pb.
Abstract: Despite their extremely good performance in solar cells with efficiencies approaching 20% and the emerging application for light-emitting devices, organic–inorganic lead halide perovskites suffer from high content of toxic, polluting, and bioaccumulative Pb, which may eventually hamper their commercialization. Here, we present the synthesis of two-dimensional (2D) Cu-based hybrid perovskites and study their optoelectronic properties to investigate their potential application in solar cells and light-emitting devices, providing a new environmental-friendly alternative to Pb. The series (CH3NH3)2CuClxBr4–x was studied in detail, with the role of Cl found to be essential for stabilization. By exploiting the additional Cu d–d transitions and appropriately tuning the Br/Cl ratio, which affects ligand-to-metal charge transfer transitions, the optical absorption in this series of compounds can be extended to the near-infrared for optimal spectral overlap with the solar irradiance. In situ formation of Cu+ ions w...

Journal ArticleDOI
TL;DR: Investigation of the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials provides new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices.
Abstract: Emission characteristics of metal halide perovskites play a key role in the current widespread investigations into their potential uses in optoelectronics and photonics However, a fundamental understanding of the molecular origin of the unusual blueshift of the bandgap and dual emission in perovskites is still lacking In this direction, we investigated the extraordinary photoluminescence behavior of three representatives of this important class of photonic materials, that is, CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3, which emerged from our thorough studies of the effects of temperature on their bandgap and emission decay dynamics using time-integrated and time-resolved photoluminescence spectroscopy The low-temperature (<100 K) photoluminescence of CH3NH3PbI3 and CH3NH3PbBr3 reveals two distinct emission peaks, whereas that of CH(NH2)2PbBr3 shows a single emission peak Furthermore, irrespective of perovskite composition, the bandgap exhibits an unusual blueshift by raising the temperature from 15 to 300 K Density functional theory and classical molecular dynamics simulations allow for assigning the additional photoluminescence peak to the presence of molecularly disordered orthorhombic domains and also rationalize that the unusual blueshift of the bandgap with increasing temperature is due to the stabilization of the valence band maximum Our findings provide new insights into the salient emission properties of perovskite materials, which define their performance in solar cells and light-emitting devices

Journal ArticleDOI
TL;DR: This study incorporates N-doped graphene nanosheets in the perovskite layer, which simultaneously induces an improved morphology and surface passivation at the perOVskite/spiro interface, resulting in enhancement in all photovoltaic parameters.
Abstract: Controlling the morphology and surface passivation in perovskite solar cells is paramount in obtaining optimal optoelectronic properties. This study incorporates N-doped graphene nanosheets in the perovskite layer, which simultaneously induces an improved morphology and surface passivation at the perovskite/spiro interface, resulting in enhancement in all photovoltaic parameters.

Journal ArticleDOI
TL;DR: Potentiodynamic and spectroelectrochemical measurements point toward a similar mechanism for the catalyst in the bound and unbound form, whereas no significant production of CO was observed from the scaffold in the absence of a molecular catalyst.
Abstract: Sunlight-driven CO2 reduction is a promising way to close the anthropogenic carbon cycle. Integrating light harvester and electrocatalyst functions into a single photoelectrode, which converts solar energy and CO2 directly into reduced carbon species, is under extensive investigation. The immobilization of rhenium-containing CO2 reduction catalysts on the surface of a protected Cu2O-based photocathode allows for the design of a photofunctional unit combining the advantages of molecular catalysts with inorganic photoabsorbers. To achieve large current densities, a nanostructured TiO2 scaffold, processed at low temperature, was deposited on the surface of protected Cu2O photocathodes. This led to a 40-fold enhancement of the catalytic photocurrent as compared to planar devices, resulting in the sunlight-driven evolution of CO at large current densities and with high selectivity. Potentiodynamic and spectroelectrochemical measurements point toward a similar mechanism for the catalyst in the bound and unbound...

Journal ArticleDOI
TL;DR: A systematic analysis of the interplay among structural features, optoelectronic performance, and ionic movement behavior for FA0.83 MA0.17 Pb(I 0.83 Br0. 17 )3 PSCs is presented, which yield high power conversion efficiencies up to 20.8%.
Abstract: Hybrid organic-inorganic perovskite materials have risen up as leading components for light-harvesting applications. However, to date many questions are still open concerning the operation of perovskite solar cells (PSCs). A systematic analysis of the interplay among structural features, optoelectronic performance, and ionic movement behavior for FA0.83 MA0.17 Pb(I0.83 Br0.17 )3 PSCs is presented, which yield high power conversion efficiencies up to 20.8%.

Journal ArticleDOI
TL;DR: A new aliphatic fluorinated amphiphilic additive is added to CH3 NH3 PbI3 perovskite to tune the morphology and enhance the environmental stability without sacrificing the performance of the devices.
Abstract: A new aliphatic fluorinated amphiphilic additive is added to CH3 NH3 PbI3 perovskite to tune the morphology and enhance the environmental stability without sacrificing the performance of the devices. Judicious screening of the perovskite precursor solution realizes a power conversion efficiency of 18.0% for mesoporous perovskite solar cells as a result of improved surface coverage. A slower degradation in ambient air is observed with this modified perovskite.

Journal ArticleDOI
TL;DR: In this article, a spiro[fluorene-9,9′-xanthene] based molecular hole-transporting materials (X59) was developed via two-step synthesis from commercial precursors for perovskite solar cells.

Journal ArticleDOI
TL;DR: Two copper bipyridyl complexes are presented as new redox couples for DSCs and the high photovoltaic performance of Cu-based redox mediators underlines the significant potential of the new red ox mediators and points to a new research and development direction for D SCs.
Abstract: Redox mediators play a major role determining the photocurrent and the photovoltage in dye-sensitized solar cells (DSCs). To maintain the photocurrent, the reduction of oxidized dye by the redox mediator should be significantly faster than the electron back transfer between TiO2 and the oxidized dye. The driving force for dye regeneration with the redox mediator should be sufficiently low to provide high photovoltages. With the introduction of our new copper complexes as promising redox mediators in DSCs both criteria are satisfied to enhance power conversion efficiencies. In this study, two copper bipyridyl complexes, Cu(II/I)(dmby)2TFSI2/1 (0.97 V vs SHE, dmby = 6,6′-dimethyl-2,2′-bipyridine) and Cu(II/I)(tmby)2TFSI2/1 (0.87 V vs SHE, tmby = 4,4′,6,6′-tetramethyl-2,2′-bipyridine), are presented as new redox couples for DSCs. They are compared to previously reported Cu(II/I)(dmp)2TFSI2/1 (0.93 V vs SHE, dmp = bis(2,9-dimethyl-1,10-phenanthroline). Due to the small reorganization energy between Cu(I) and ...

Journal ArticleDOI
TL;DR: The family of solution-processed tin-based perovskites is demonstrated as a new and superior near-infrared gain medium due to the large electron-hole bimolecular recombination associated with tin and the reduced trap density with SnF2 treatment.
Abstract: The family of solution-processed tin-based perovskites is demonstrated as a new and superior near-infrared gain medium. Due to the large electron-hole bimolecular recombination associated with tin and the reduced trap density with SnF2 treatment, these lead-free "green" perovskites yield stable coherent light emission extending to ≈1 μm at strikingly low thresholds.

Journal ArticleDOI
TL;DR: In this article, the ionic liquid driven crystallization was exploited to produce a planar perovskite solar cell with a stabilized power output of 19.5% for the first time.
Abstract: Ionic liquids can retard the perovskite crystallization with the aim to form compact films with larger and more uniformly distributed grain size. The ionic liquid driven crystallization is exploited to prepared a record planar perovskite solar cell with stabilized power output of 19.5%.

Journal ArticleDOI
TL;DR: In this paper, the influence of monovalent cation halide additives on the optical, excitonic, and electrical properties of CH3NH3PbI3 perovskite is reported.
Abstract: The influence of monovalent cation halide additives on the optical, excitonic, and electrical properties of CH3NH3PbI3 perovskite is reported. Monovalent cation halide with similar ionic radii to Pb2+, including Cu+, Na+, and Ag+, have been added to explore the possibility of doping. Significant reduction of sub-bandgap optical absorption and lower energetic disorder along with a shift in the Fermi level of the perovskite in the presence of these cations has been observed. The bulk hole mobility of the additive-based perovskites as estimated using the space charge limited current method exhibits an increase of up to an order of magnitude compared to the pristine perovskites with a significant decrease in the activation energy. Consequentially, enhancement in the photovoltaic parameters of additive-based solar cells is achieved. An increase in open circuit voltage for AgI (approximate to 1.02 vs 0.95 V for the pristine) and photocurrent density for NaI- and CuBr-based solar cells (approximate to 23 vs 21 mA cm(-2) for the pristine) has been observed. This enhanced photovoltaic performance can be attributed to the formation of uniform and continuous perovskite film, better conversion, and loading of perovskite, as well as the enhancement in the bulk charge transport along with a minimization of disorder, pointing towards possible surface passivation.

Journal ArticleDOI
TL;DR: In this paper, a high efficiency perovskite solar cell with a hybrid hole-transporting material counter electrode based on a thin single-walled carbon nanotube (SWCNT) film and a drop-cast 2,2,7,-7,7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) hole transporting material (HTM) was demonstrated.
Abstract: We demonstrate a high efficiency perovskite solar cell with a hybrid hole-transporting material-counter electrode based on a thin single-walled carbon nanotube (SWCNT) film and a drop-cast 2,2,7,-7-tetrakis(N,N-di-p-methoxyphenylamine)-9,9′-spirobifluorene (Spiro-OMeTAD) hole-transporting material (HTM). The average efficiency of the solar cells was 13.6%, with the record cell yielding 15.5% efficiency. The efficiency of the reference solar cells with spin-coated Spiro-OMeTAD hole-transporting materials (HTMs) and an evaporated gold counter electrode was 17.7% (record 18.8%), that of the cells with only a SWCNT counter electrode (CE) without additional HTM was 9.1% (record 11%) and that of the cells with gold deposited directly on the perovskite layer was 5% (record 6.3%). Our results show that it is possible to manufacture high efficiency perovskite solar cells with thin film (thickness less than 1 μm) completely carbon-based HTM-CEs using industrially upscalable manufacturing methods, such as press-transferred CEs and drop-cast HTMs.

Journal ArticleDOI
TL;DR: The nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices are mapped and a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer is combined with Kelvin probe force microscopy to provide unprecedented understanding of the nanoscales perovSKite composition.
Abstract: Compositional engineering of a mixed cation/mixed halide perovskite in the form of (FAPbI3)0.85(MAPbBr3)0.15 is one of the most effective strategies to obtain record-efficiency perovskite solar cells. However, the perovskite self-organization upon crystallization and the final elemental distribution, which are paramount for device optimization, are still poorly understood. Here we map the nanoscale charge carrier and elemental distribution of mixed perovskite films yielding 20% efficient devices. Combining a novel in-house-developed high-resolution helium ion microscope coupled with a secondary ion mass spectrometer (HIM-SIMS) with Kelvin probe force microscopy (KPFM), we demonstrate that part of the mixed perovskite film intrinsically segregates into iodide-rich perovskite nanodomains on a length scale of up to a few hundred nanometers. Thus, the homogeneity of the film is disrupted, leading to a variation in the optical properties at the micrometer scale. Our results provide unprecedented understanding ...

Journal ArticleDOI
TL;DR: In this article, the authors present a Web of Science Record created on 2016-10-18, modified on 2017-05-12, with the purpose of obtaining a record.
Abstract: Reference EPFL-ARTICLE-222354doi:10.1002/aenm.201600401View record in Web of Science Record created on 2016-10-18, modified on 2017-05-12

Journal ArticleDOI
TL;DR: In this article, a block-copolymer templated chemical solution deposition is used to prepare mesoporous Nd-doped TiO2 electrodes for perovskite-based solar cells.
Abstract: Block-copolymer templated chemical solution deposition is used to prepare mesoporous Nd-doped TiO2 electrodes for perovskite-based solar cells. X-ray diffraction and photothermal deflection spectroscopy show substitutional incorporation into the TiO2 crystal lattice for low Nd concentration, and increasing interstitial doping for higher concentrations. Substitutional Nd-doping leads to an increase in stability and performance of perovskite solar cells by eliminating defects and thus increasing electron transport and reducing charge recombination in the mesoporous TiO2. The optimized doping concentration of 0.3% Nd enables the preparation of perovskite solar cells with stabilized power conversion effi ciency of > 18%.

Journal ArticleDOI
TL;DR: A new method of producing high-quality perovskite films via sequential deposition is presented, introducing a PbX2 capping layer that is endowed with a network of interconnected nanopores.
Abstract: A new method of producing high-quality perovskite films via sequential deposition is presented, introducing a PbX2 capping layer that is endowed with a network of interconnected nanopores. The mesoporous lead halide architecture provides a powerful tool to accomplish rapid and complete transformation of lead halide into the perovskite for high-efficiency solar cells.