Stability Issues on Perovskite Solar Cells
TL;DR: In this paper, the authors discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of pervskite solar cell, which is a promising next generation photovoltaic technology.
Abstract: Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide (HC(NH2)2PbI3) show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell.
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TL;DR: In this article, the authors demonstrate that ionic defects, migrating on timescales significantly longer (above 103 s) than what has so far been explored (from 10−1 to 102 s), abate the initial efficiency by 10−15% after several hours of operation at the maximum power point.
Abstract: Perovskites have been demonstrated in solar cells with a power conversion efficiency of well above 20%, which makes them one of the strongest contenders for next generation photovoltaics. While there are no concerns about their efficiency, very little is known about their stability under illumination and load. Ionic defects and their migration in the perovskite crystal lattice are some of the most alarming sources of degradation, which can potentially prevent the commercialization of perovskite solar cells (PSCs). In this work, we provide direct evidence of electric field-induced ionic defect migration and we isolate their effect on the long-term performance of state-of-the-art devices. Supported by modelling, we demonstrate that ionic defects, migrating on timescales significantly longer (above 103 s) than what has so far been explored (from 10−1 to 102 s), abate the initial efficiency by 10–15% after several hours of operation at the maximum power point. Though these losses are not negligible, we prove that the initial efficiency is fully recovered when leaving the device in the dark for a comparable amount of time. We verified this behaviour over several cycles resembling day/night phases, thus probing the stability of PSCs under native working conditions. This unusual behaviour reveals that research and industrial standards currently in use to assess the performance and the stability of solar cells need to be adjusted for PSCs. Our work paves the way for much needed new testing protocols and figures of merit specifically designed for PSCs.
487 citations
TL;DR: The assembly of CsPbBr3 QD/AlOx inorganic nanocomposites, by using atomic layer deposition (ALD) for the growth of the amorphous alumina matrix (AlOx), is described as a novel protection scheme for such QDs.
Abstract: Herein, the assembly of CsPbBr3 QD/AlOx inorganic nanocomposite, using atomic layer deposition (ALD) for the growth of the amorphous alumina matrix (AlOx), is proven as a novel protection scheme for this new class of QDs. The nucleation and growth process of AlOx on the QD surface was thoroughly investigated by a miscellanea of techniques which highlighed the importance of the interaction between the ALD precursor and the QD surface to uniformely coat the QDs while preserving the optoelectronic properties. These nanocomposites show an exceptional stability against exposure to air (for at least 45 days), irradiation under simulated solar spectrum (for at least 8h), to thermal treatment (at least up to 200oC in air), and finally against immersion in water. The method was extended to assembly CsPbBrxI3-x QD/AlOx and CsPbI3 QD/AlOx nanocomposites which were more stable compared to the pristine QD films.
362 citations
TL;DR: A thorough overview of state of the art of stability of perovskite solar cells and important degradation issues involved in this technology are discussed in this paper. But the degradation mechanisms resulting from thermal and chemical instabilities, phase transformations, exposure to visible and UV light, moisture and oxygen and most importantly sealing issues are thoroughly analyzed.
Abstract: This work provides a thorough overview of state of the art of stability of perovskite solar cells (PSCs) and covers important degradation issues involved in this technology. Degradation factors, which are reported in the literature affecting the stability of PSCs, are discussed. Several degradation mechanisms resulting from thermal and chemical instabilities, phase transformations, exposure to visible and UV light, moisture and oxygen and most importantly sealing issues are thoroughly analyzed. Methods are suggested to study most of these degradation mechanisms in a systematic way. In addition, environmental assessment of PSCs is briefly covered. Alternative materials and their preparation methods are screened with respect to stability of the device. Overall, this work contributes in developing better understanding of the degradation mechanisms and help in improving overall stability of the PSCs.
342 citations
Cites background from "Stability Issues on Perovskite Sola..."
..., are very significant for improving the thermal stability of the PSCs [172], [183], [184]....
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...The thermal instability of PSC may originate from either intrinsic instability of perovskite film or HTM layer [172]....
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TL;DR: In this paper, the authors provide an overview of state-of-the-art progress on the integrated solar cell devices based on DSSC and PSC, such as DSSCs/LIB, DSSc/PESC, PSC/PSC, SSC/SSC, OSC/SC, PSSC/SC/OSC, DSC/NG, NSC/NSC, PSC/NSCS, and PESC/ELC, for energy harvesting and storage.
Abstract: The sharp increase of research passion in the new-generation solar cells in recent years has resulted in a new trend in combining multiple types of energy devices in a single device. In view of the enhanced and/or diversified function of integrated devices, as compared with conventional devices with limited performance or sole applicability, many integrated power packs have been widely developed by combining different devices, such as a silicon solar cell (SSC), Cu(In,Ga)(Sn,Se)2 (CIGS), organic solar cell (OSC), dye-sensitized solar cell (DSSC), perovskite solar cell (PSC), lithium-ion battery (LIB), nanogenerator (NG), supercapacitor (SC), photoelectrosynthetic cell (PESC), and electrolysis cell (ELC), into one unit. In this Review, with a particular emphasis on their recent advances, we cover the integrated solar cell device research in a broad sense and provide an overview of state-of-the-art progress on the integrated solar cell devices based on DSSC and PSC, such as DSSC/LIB, DSSC/SC, DSSC/NG, DSSC/LIB/NG, PSC/OSC, PSC/CIGS, PSC/PSC, PSC/SSC, SSC/SC, PSC/SC, OSC/SC, DSSC/PESC, PSC/PESC, and PSC/ELC, for energy harvesting and storage that are significantly important for self-powering systems and portable/wearable electronics. Finally, the challenges and future outlooks in this promising photovoltaic (PV) field are featured on the basis of current development.
339 citations
TL;DR: Using direct calorimetric measurement of heats of formation, MAPbI3 is shown to be thermodynamically unstable with respect to decomposition to lead iodide and methylammonium iodide, thus limiting its long-term use in devices.
Abstract: Hybrid perovskites, especially methylammonium lead iodide (MAPbI3), exhibit excellent solar power conversion efficiencies. However, their application is plagued by poor chemical and structural stability. Using direct calorimetric measurement of heats of formation, MAPbI3 is shown to be thermodynamically unstable with respect to decomposition to lead iodide and methylammonium iodide, even in the absence of ambient air or light or heat-induced defects, thus limiting its long-term use in devices. The formation enthalpy from binary halide components becomes less favorable in the order MAPbCl3, MAPbBr3, MAPbI3, with only the chloride having a negative heat of formation. Optimizing the geometric match of constituents as measured by the Goldschmidt tolerance factor provides a potentially quantifiable thermodynamic guide for seeking chemical substitutions to enhance stability.
314 citations
Cites background from "Stability Issues on Perovskite Sola..."
...A review by Zhao and Park (11) describes several aspects of MAPbI3 degradation including photostability, thermal stability, and stability in the presence of ambient air (O2/H2O)....
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...Zhao X, Park NG (2015) Stability issues on perovskite solar cells....
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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
"Stability Issues on Perovskite Sola..." refers methods in this paper
...The basic structure of solid-state PSC comes from the solid-state DSSC employing organic hole transport material (HTM) of 2,2′,7,7′-tetrakis(N,N-dimethoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) [5]....
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...PSCs based on liquid electrolytes were reported by Miyasaka et al. in 2009 [1], and by Park et al. in 2011 [2], where methylammonium lead halide (MAPbX3, MA = CH3NH3, X = I or Br) was used as an inorganic sensitizer similar to the organic sensitizer like N719 in dye-sensitized solar cell (DSSC) [3]....
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...in 2011 [2], where methylammonium lead halide (MAPbX3, MA = CH3NH3, X = I or Br) was used as an inorganic sensitizer similar to the organic sensitizer like N719 in dye-sensitized solar cell (DSSC) [3]....
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...Han’s group fabricated a mesoscopic TiO2/ZrO2/MAPbI3 solar cell with carbon black/spheroidal graphite electrode like monolithic DSSC [37]....
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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: A low-cost, solution-processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight is reported.
Abstract: The energy costs associated with separating tightly bound excitons (photoinduced electron-hole pairs) and extracting free charges from highly disordered low-mobility networks represent fundamental losses for many low-cost photovoltaic technologies. We report a low-cost, solution-processable solar cell, based on a highly crystalline perovskite absorber with intense visible to near-infrared absorptivity, that has a power conversion efficiency of 10.9% in a single-junction device under simulated full sunlight. This "meso-superstructured solar cell" exhibits exceptionally few fundamental energy losses; it can generate open-circuit photovoltages of more than 1.1 volts, despite the relatively narrow absorber band gap of 1.55 electron volts. The functionality arises from the use of mesoporous alumina as an inert scaffold that structures the absorber and forces electrons to reside in and be transported through the perovskite.
9,158 citations
TL;DR: A sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film that greatly increases the reproducibility of their performance and allows the fabrication of solid-state mesoscopic solar cells with unprecedented power conversion efficiencies and high stability.
Abstract: Following pioneering work, solution-processable organic-inorganic hybrid perovskites-such as CH3NH3PbX3 (X = Cl, Br, I)-have attracted attention as light-harvesting materials for mesoscopic solar cells. So far, the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using a mixture of PbX2 and CH3NH3X in a common solvent. However, the uncontrolled precipitation of the perovskite produces large morphological variations, resulting in a wide spread of photovoltaic performance in the resulting devices, which hampers the prospects for practical applications. Here we describe a sequential deposition method for the formation of the perovskite pigment within the porous metal oxide film. PbI2 is first introduced from solution into a nanoporous titanium dioxide film and subsequently transformed into the perovskite by exposing it to a solution of CH3NH3I. We find that the conversion occurs within the nanoporous host as soon as the two components come into contact, permitting much better control over the perovskite morphology than is possible with the previously employed route. Using this technique for the fabrication of solid-state mesoscopic solar cells greatly increases the reproducibility of their performance and allows us to achieve a power conversion efficiency of approximately 15 per cent (measured under standard AM1.5G test conditions on solar zenith angle, solar light intensity and cell temperature). This two-step method should provide new opportunities for the fabrication of solution-processed photovoltaic cells with unprecedented power conversion efficiencies and high stability equal to or even greater than those of today's best thin-film photovoltaic devices.
8,427 citations
"Stability Issues on Perovskite Sola..." refers background in this paper
...Almost at the same time, both Snaith’s group and Grätzel’s group achieved an efficiency of ~15% [7,8]....
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TL;DR: It is shown that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.
Abstract: Many different photovoltaic technologies are being developed for large-scale solar energy conversion. The wafer-based first-generation photovoltaic devices have been followed by thin-film solid semiconductor absorber layers sandwiched between two charge-selective contacts and nanostructured (or mesostructured) solar cells that rely on a distributed heterojunction to generate charge and to transport positive and negative charges in spatially separated phases. Although many materials have been used in nanostructured devices, the goal of attaining high-efficiency thin-film solar cells in such a way has yet to be achieved. Organometal halide perovskites have recently emerged as a promising material for high-efficiency nanostructured devices. Here we show that nanostructuring is not necessary to achieve high efficiencies with this material: a simple planar heterojunction solar cell incorporating vapour-deposited perovskite as the absorbing layer can have solar-to-electrical power conversion efficiencies of over 15 per cent (as measured under simulated full sunlight). This demonstrates that perovskite absorbers can function at the highest efficiencies in simplified device architectures, without the need for complex nanostructures.
7,018 citations
"Stability Issues on Perovskite Sola..." refers background in this paper
...Almost at the same time, both Snaith’s group and Grätzel’s group achieved an efficiency of ~15% [7,8]....
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