In recent years, the record efficiency of perovskite solar cells (PSCs) has been updated from 9.7% to 20.1%. However, there has been very little study of the issue of stability, which restricts the ...outdoor application of PSCs. The issues of the degradation of perovskite and the stability of PSC devices should be urgently addressed to achieve good reproducibility and long lifetimes for PSCs with high conversion efficiency. Without studies on stability, exciting achievements cannot be transferred from the laboratory to industry and outdoor applications. In order to improve their stability, a basic understanding of the degradation process of PSCs in different conditions should be acquired
via
thorough study. This review summarizes recent studies of the relationship of the chemical stability of PSCs with their environment (oxygen and moisture, UV light, solution process, temperature) and corresponding possible solutions.
The understanding of how the chemical stability of PSCs is affected by oxygen and moisture, UV light, the solution process, and temperature was reviewed.
Perovskite solar cells (PSCs) have recently demonstrated high efficiencies of over 22%, but the thermal stability is still a major challenge for commercialization. In this work, the thermal ...degradation process of the inverted structured PSCs induced by the silver electrode is thoroughly investigated. Elemental depth profiles indicate that iodide and methylammonium ions diffuse through the electron‐trasnporting layer and accumulate at the Ag inner surface. The driving force of forming AgI then facilitates the ions extraction. Variations on the morphology and current mapping of the MAPbI3 thin films upon thermal treatment reveal that the loss of ions occurs at the grain boundaries and leads to the reconstruction of grain domains. Consequently, the deteriorated MAPbI3 thin film, the poor electron extraction, and the generation of AgI barrier result in the degradation of efficiencies. These direct evidences provide in‐depth understanding of the effect of thermal stress on the devices, offering both experimental support and theoretical guidance for the improvement on the thermal stability of the inverted PSCs.
Silver‐electrode‐induced thermal degradation of the inverted perovskite solar cells is investigated with direct evidences. The diffusion of iodide and methylamine ions is directly observed in the elemental depth profile during thermal treatment only when the Ag electrode is introduced. The loss of ions leads to the reconstruction of the grain boundaries and forming thick PbI2 gaps between crystal grains.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The highly developed crystallization process with respect to perovskite thin films is favorable for efficient solar cells. Here, an innovative intermolecular self-assembly approach was employed to ...retard the crystallization of PbI2 in dimethylformamide (DMF) by additional solvent of dimethyl sulfoxide (DMSO), which was proved to be capable of coordinating with PbI2 by coordinate covalent bond. The obtained PbI2(DMSO) x (0 ≤ x ≤ 1.86) complexes tend to be closely packed by means of intermolecular self-assembly. Afterward, an intramolecular exchange of DMSO with CH3NH3I (MAI) enabled the complexes to deform their shape and finally to reorganize to be an ultraflat and dense thin film of CH3NH3PbI3. The controllable grain morphology of perovskite thin film allows obtaining a power conversion efficiency (PCE) above 17% and a stabilized power output above 16% within 240 s by controlling DMSO species in the complex–precursor system (CPS). The present study gives a reproductive and facile strategy toward high quality of perovskite thin films and efficient solar cells.
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IJS, KILJ, NUK, PNG, UL, UM
The perovskite solar cell has emerged rapidly in the field of photovoltaics as it combines the merits of low cost, high efficiency, and excellent mechanical flexibility for versatile applications. ...However, there are significant concerns regarding its operational stability and mechanical robustness. Most of the previously reported approaches to address these concerns entail separate engineering of perovskite and charge-transporting layers. Herein we present a holistic design of perovskite and charge-transporting layers by synthesizing an interpenetrating perovskite/electron-transporting-layer interface. This interface is reaction-formed between a tin dioxide layer containing excess organic halide and a perovskite layer containing excess lead halide. Perovskite solar cells with such interfaces deliver efficiencies up to 22.2% and 20.1% for rigid and flexible versions, respectively. Long-term (1000 h) operational stability is demonstrated and the flexible devices show high endurance against mechanical-bending (2500 cycles) fatigue. Mechanistic insights into the relationship between the interpenetrating interface structure and performance enhancement are provided based on comprehensive, advanced, microscopic characterizations. This study highlights interface integrity as an important factor for designing efficient, operationally-stable, and mechanically-robust solar cells.
Organic–inorganic hybrid perovskite solar cells are found to be sensitive to moisture, oxygen, UV light, light soaking, heat, electric field, etc. Among all these factors, thermal stability is one of ...the most challenging concerns affecting PSCs stability, since it is hard to avoid a temperature increase for solar cells during operation. In this work, we systematically studied the thermal stability of Cs x MA 1−x PbI 3 film and solar cells. The introduction of Cs into the precursor solution would inevitably accelerate the film deposition rate, resulting in decreased grain size and more Cs atoms in the film than in the precursors. The study on thermal stability illustrated that perovskite degradation was highly related to the amount of oxygen in the air. A small amount of Cs doping ( x = 0.09) was beneficial for better thermal stability. In addition, Cs doping also enhanced the device performance. The improvement of short-circuit currents came from the increased film thickness, which was due to the faster deposition rate for Cs doped samples. Besides, Cs doping was vital to suppress the trap states in the film since the trap states were related to halide deficiency during thermal annealing. At last, the final performance of Cs 0.09 MA 0.91 PbI 3 reached 18.1%, with a J SC of 22.57 mA cm −2 , V OC of 1.06 V, FF of 0.76.
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IJS, KILJ, NUK, UL, UM, UPUK
Lighting accounts for one-fifth of global electricity consumption
. Single materials with efficient and stable white-light emission are ideal for lighting applications, but photon emission covering ...the entire visible spectrum is difficult to achieve using a single material. Metal halide perovskites have outstanding emission properties
; however, the best-performing materials of this type contain lead and have unsatisfactory stability. Here we report a lead-free double perovskite that exhibits efficient and stable white-light emission via self-trapped excitons that originate from the Jahn-Teller distortion of the AgCl
octahedron in the excited state. By alloying sodium cations into Cs
AgInCl
, we break the dark transition (the inversion-symmetry-induced parity-forbidden transition) by manipulating the parity of the wavefunction of the self-trapped exciton and reduce the electronic dimensionality of the semiconductor
. This leads to an increase in photoluminescence efficiency by three orders of magnitude compared to pure Cs
AgInCl
. The optimally alloyed Cs
(Ag
Na
)InCl
with 0.04 per cent bismuth doping emits warm-white light with 86 ± 5 per cent quantum efficiency and works for over 1,000 hours. We anticipate that these results will stimulate research on single-emitter-based white-light-emitting phosphors and diodes for next-generation lighting and display technologies.
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KISLJ, NUK, SBMB, UL, UM, UPUK
The interface modification of perovskite thin films has shown great potential to boost the performance of perovskite solar cells during the last few years. Here we demonstrate that cesium chloride ...(CsCl) as crystal seeds can markedly enhance the coverage of the CH3NH3PbI3-xClx absorber layer on TiO2 in planar heterojunction solar cells, thus boosting the power conversion efficiency (PCE) to 16.8%, with a fill factor (FF) of 0.79. Also, the introduction of CsCl significantly improved the stability of CH3NH3PbI3-xClx under ultra violet (UV) irradiation, which has been verified by XRD, XPS and SEM measurements. The CsCl-treated devices maintained 70% of the original PCE after a prolonged intensive UV irradiation of 200 min while the untreated devices being almost exhausted. Furthermore, we proposed the mechanism concerning CsCl as the modification layer to improve the UV-induced stability issue of perovskite solar cells.
Recently, the stability of organic–inorganic perovskite thin films under thermal, photo, and moisture stresses has become a major concern for further commercialization due to the high volatility of ...the organic cations in the prototype perovskite composition (CH3NH3PbI3). All inorganic cesium (Cs) based perovskite is an alternative to avoid the release or decomposition of organic cations. Moreover, substituting Pb with Sn in the organic–inorganic lead halide perovskites has been demonstrated to narrow the bandgap to 1.2–1.4 eV for high‐performance perovskite solar cells. In this work, a series of CsPb1−xSnxIBr2 perovskite alloys via one‐step antisolvent method is demonstrated. These perovskite films present tunable bandgaps from 2.04 to 1.64 eV. Consequently, the CsPb0.75Sn0.25IBr2 with homogeneous and densely crystallized morphology shows a remarkable power conversion efficiency of 11.53% and a high Voc of 1.21 V with a much improved phase stability and illumination stability. This work provides a possibility for designing and synthesizing novel inorganic halide perovskites as the next generation of photovoltaic materials.
The authors demonstrate CsPb1−xSnxIBr2 alloys that could be used as wide‐band gap absorbers for perovskite solar cells. The CsPb1−xSnxIBr2 films show tunable bandgaps from 2.04 eV to 1.64 eV. A remarkable power conversion efficiency of 11.53% and a high open‐circuit voltage of 1.21 V are achieved by the CsPb0.75Sn0.25IBr2 derived device, meanwhile with improved phase stability and photo‐stability under illumination.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Organic-inorganic hybrid photodetectors attract considerable attention because they can combine the advantages of both organic and inorganic systems. Here, a perovskite compound with a broad ...absorption spectrum and high power conversion efficiency is used as a photosensitive layer in an organic/inorganic hybrid heterojunction photodetector with a high and fast response. The high sensitivity exceeding 10(4) is obtained at bias of 0-4 V. Using a tandem organic light-emitting diode (OLED) as the light source, we fabricated an optocoupler device. The optocoupler achieved a maximum photoresponsivity of 1.0 A W(-1) at 341.3 μWcm(-2) at an input voltage of 6 V. The device also exhibits rapid response times of τ(rise) ~ 20 μs and τ(fall) ~ 17 μs; as well as a high current transfer ratio (CTR) of 28.2%. After applying an amplification circuit, the CTR of the optocoupler increases to 263.3%, which is comparable with that of commercial inorganic optocouplers. The developed hybrid optocoupler thus shows great promise for use in photonics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Solar cells based on organic inorganic hybrid metal halide perovskites have exhibited a rapid increase of power conversion efficiency (PCE). Perovskite solar cells involving mixed cations, especially ...recently reported Cs doping, have shown huge potential to improve PCE as well as device stability. However, when doping Cs into CH3NH3PbI3 (MAPbI3) and HC(NH2)23PbI3 (FAPbI3), CsPbI3 could segregate from the perovskite phase, affecting the performance negatively. In addition, despite improved charge transfer was predicted for oriented film along / directions, the fabrication is still on the way and rarely reported. Herein, an ultra-smooth perovskite film oriented along / directions is created for the first time, with a homogeneous tetragonal phase of (MAPbI3)1−x(CsPbBr3)x. The preferentially precipitated heavily Cs-doped perovskite, and the lowered surface energy of (112) and (200) planes, verified by DFT calculations, are responsible for the orientation. The improved charge transfer and suppressed trap states in the oriented film substantially improved the performance. Upon an optimal doping ratio of 0.1, a PCE of 17.6% was achieved, together with remarkable improvements in stability under UV irradiance and in ambient atmosphere.
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•Ultra-smooth perovskite films oriented along / directions is fabricated.•Preferentially precipitated Cs-doped perovskite is responsible for the orientation.•The special orientation improved the charge transfer and suppressed the trap states.•We achieved a PCE of 17.6%, with improvements in stability under UV irradiance.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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