Abstract
The long-term stability of perovskite solar cells remains one of the most important challenges for the commercialization of this emerging photovoltaic technology. Here, we adopt a non-noble ...metal/metal oxide/polymer multiple-barrier to suppress the halide consumption and gaseous perovskite decomposition products release with the chemically inert bismuth electrode and Al
2
O
3
/parylene thin-film encapsulation, as well as the tightly closed system created by the multiple-barrier to jointly suppress the degradation of perovskite solar cells, allowing the corresponding decomposition reactions to reach benign equilibria. The resulting encapsulated formamidinium cesium-based perovskite solar cells with multiple-barrier maintain 90% of their initial efficiencies after continuous operation at 45 °C for 5200 h and 93% of their initial efficiency after continuous operation at 75 °C for 1000 h under 1 sun equivalent white-light LED illumination.
Perovskite solar cells (PSCs) are promising candidates for further photovoltaic technology. However, the instability issue remains a major obstacle hampering their commercialization. Since ...perovskites are sensitive to external stressors including elevated temperature, humidity, and light, and the decomposition of perovskite under these combined stressors could largely aggravate and accelerate PSCs degradation, the stability aging test under combined stressors has been recognized as the harshest and the most important requirements for PSCs stability evaluation. Herein, the degradation mechanisms of PSCs at elevated temperature, humidity, and light illumination conditions are analyzed. Further, the recent progress on improving the stability of PSCs under combined stressors including 85% relative humidity/85 °C damp heat aging test and light and elevated temperature induced degradation aging test is summarized. The predictions for the further development of effective strategies for improving the stability of PSCs are provided at the end of this review.
The recent progress on perovskite compositions, charge transfer materials, the interface modification layers, inert electrodes, and encapsulations for improving perovskite solar cells’ stability under 85% relative humidity/85 °C damp heat aging test and light and elevated temperature‐induced degradation aging test is summarized. The differences and key difficulties in passing these two kinds of harsh stability tests are specifically highlighted.
Cost-effective and stable CsPbBr3-based inorganic perovskite solar cells (PSCs) are regarded as promising candidates for next-generation photovoltaics. However, the large interfacial energy ...differences at the CsPbBr3/hole-transporting layer lead to serious charge recombination and poor charge extraction kinetics. Herein, we prepare a series of hole-transporting materials (HTMs) to improve hole extraction and to reduce electron–hole recombination at the CsPbBr3/HTM interface. In comparison with the power conversion efficiency (PCE) of 6.10% for an HTM-free device, the CsPbBr3 PSCs with polymeric HTMs such as polythiophene, polypyrrole and polyaniline yield efficiencies of 8.36%, 8.32% and 7.69%, respectively. Similarly, the inorganic PSC with organic small molecule BT-BTH achieves a PCE as high as 9.32% due to the improved hole conductivity. Moreover, the unencapsulated PSC with BT-BTH maintains 94% of its initial efficiency in 70% relative humidity over 80 days.
Organic ammonium salts have been widely used for defect passivation to suppress nonradiative charge recombination in perovskite solar cells (PSCs). However, they are prone to form undesirable ...in‐plane favored 2D perovskites with poor charge transport capability that hamper device performance. Herein, the defects passivation role of alkyldiammonium including 1.6‐hexamethylenediamine dihydriodide (HDAI2), 1,3‐propanediamine dihydriodide (PDAI2), and 1.4‐butanediamine dihydriodide (BDAI2) for formamidinium‐cesium perovskite is systematically investigated. With help of density functional theory (DFT) calculations, BDA with suitable size can synergistically passivate two defect sites on perovskite surfaces, showing the best defect passivation effect among the above three alkyldiammonium salts. Perovskite films based on BDAI2 modification are found to keep the 3D perovskite phase with considerably reduced trap‐state density, and enhanced carrier extraction. As a result, the BDAI2‐modified devices deliver impressive efficiencies of 23.1% and 20.9% for inverted PSCs on the rigid and flexible substrates, respectively. Moreover, the corresponding encapsulated rigid devices maintain 92% of the initial efficiency after operating under continuous 1‐sun illumination with the maximum power point tracking for 1000 h. Furthermore, the mechanical flexibility of the BDAI2‐modified flexible device is also improved due to the release of residual stress.
BDA can make full use of the two ammonium cations for passivation and strengthen the absorption of BDA onto the VFA defect as well as enhance the formation energy of VFA, and thereby anchor the perovskite surfaces, so as to improve the photovoltaic performance of rigid and flexible devices.
Inverted perovskite solar cells (PSCs) based on formamidinium-cesium (FACs) perovskites with nickel oxide as hole transport layer (HTL) have attracted much attention due to their good stability. ...However, their open-circuit voltage (VOC) and efficiencies lag far behind those of inverted PSCs based on organic HTLs. Here, we introduce an organic dye coumarin 343 (C343) as a molecular additive into the perovskite to reduce VOC loss and improve the efficiency of nickel oxide-based inverted PSCs. We demonstrate that the strong coordination between the carboxyl groups in C343 and under-coordinated Pb2+ not only optimizes perovskite crystal growth during perovskite formation, but also reduces the defects densities within perovskite films. As a result, our C343 doped PSCs achieve an optimal efficiency of 20.9% (certified 20.2%), which is one of the highest efficiencies for FACs perovskite and nickel oxide based inverted PSCs reported so far. Moreover, the utilization of C343 also benefits devices’ stability, making the devices maintain over 94% and 95% of the initial PCE after aging at 85 °C for 500 h in N2 glovebox and operation under continuous 1 sun illumination with the maximum power point (MPP) tracking at the temperature around 65 °C in ambient air for 500 h, respectively.
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•Coumarin 343 can optimize perovskite crystal growth and passivate defects by its coordination with uncoordinated Pb2+ ions.•Coumarin 343 is demonstrated to improve the thermal stability and operational stability of the devices.•PCEs up to 20.94% (certified 20.2%) are achieved for nickel oxide-based formamidinium-cesium perovskite solar cells.
Perovskite solar cells (PSCs) require both high efficiency and reliable long-term stability for commercialization. As important as the perovskite layer, charge transport layers and their contact with ...the adjacent perovskite layer also play crucial roles in the efficiency and stability of PSCs. Herein, we report the use of pyridine anchoring group functionalized poly(triarylamine) (p-PY) as the hole transport layer at buried interfaces between the conductive oxide substrate and formamidinium-cesium perovskite layer to enhance the efficiency and stability of inverted PSCs. The p-PY based device exhibited a record efficiency of 22.8% (certified efficiency of 22.3%) and maintained 97.5% of the initial efficiency after operation under 1 sun equivalent white-light light-emitting diode array illumination with maximum power point tracking at 45 °C for 1000 h, and 94% and 81% of the initial efficiencies after harsh thermal aging at 85 °C for 500 h and at 120 °C for 200 h, respectively.
Herein, we report the use of pyridine anchoring group functionalized poly(triarylamine) (p-PY) as a hole transport layer at buried interfaces between the ITO and formamidinium-cesium perovskite layer to enhance the efficiency and stability of inverted PSCs.
In perovskite solar cells, the formation of residual/excess lead iodide (PbI
2
) in the perovskite film is detrimental to device stability. However, the understanding of the effect of residual/excess ...PbI
2
and its distribution on perovskite degradation is still insufficient. Herein, we verify that the existence of residual PbI
2
near the buried interface largely deteriorates perovskite stability. By using a pre-embedding mixed A-cation halide strategy, the residual unstable PbI
2
near the buried interface is transformed into a more stable 3D perovskite for stability improvement. Moreover, this strategy could balance the lattice strain of the formamidinium-based perovskite near the buried interface, suppress the detrimental α to δ phase transition and improve perovskite phase stability. As a result, promising power conversion efficiencies of 24.26% and 20.97% are obtained for perovskite solar cells and modules, respectively. In addition, the solar cells maintain 94.7% of their initial efficiencies after operating for 1000 hours under one sun illumination.
A pre-embedding mixed A-cation halide strategy is developed to eliminate the residual unstable PbI
2
and lattice strain near the buried interface of the perovskite layer for the stability improvement of formamidinium-based perovskite solar cells.
Perovskite solar cells (PSCs) have attracted great attention due to their rapidly improved power conversion efficiency (PCE), which is up to 25.5%, comparable to commercial Si-based solar cells. ...Currently, stability is one of the key obstacles to their commercialization. Compared with organic-inorganic PSCs with volatile organic components, all-inorganic PSCs exhibit excellent thermal stability, and thus have attracted more and more attention in recent years. Among them, PSCs based on CsPbI
3
perovskite are the most eye-catching because of its ideal bandgap (1.73 eV) and excellent light absorption. Here, we systematically review strategies to improve the efficiency and stability of CsPbI
3
PSCs from their early days to recent advances. The improvement mechanisms are discussed from the aspects of film formation technology, additive engineering, dimensionality engineering, doping engineering and quantum dot technology. In the end, the future development direction and obstacles of CsPbI
3
PSCs are also discussed.
Additive engineering, dimensionality engineering, doping engineering and quantum dot technology can effectively improve the efficiency and stability of the most eye-catching all-inorganic CsPbI
3
based PSCs.
•A finely-controlled CVD deposition of hydrophobic Parylene C polymer is conducted to form the interlayer in inverted PSCs.•Parylene polymer can also serve as a wide-bandgap and insulated tunneling ...layer to inhibit interfacial charge recombination and benefit the charge transfer and the chloride group chemically react with the undercoordinated lead centers and decrease the defects of the device.•The Parylene C modified devices yield impressive long-term stability and reproducibility, both of which are important features urgently required by the industrialization of PSCs.
Perovskite solar cells (PSCs) have been shining in the photovoltaic industry, but their fragile stability impedes their commercialization seriously. Here we adopt an ultra-thin film of a functional hydrophobic polymer, polychloro-p-dimethyl benzene (Parylene C), which can largely improve the operational lifetime of PSCs as a surface finish. Chemical vapor deposition (CVD) under vacuum is adopted to modify the ultra-thin parylene film, which is thin adequately to afford tunnel contact but is also sufficiently shielding to protect the perovskite layer. Besides, it is demonstrated that the Parylene C film can reduce the perovskite surface defects by interacting with the uncoordinated Pb center and act as an effective hole-hindering barrier in the middle of perovskite and PCBM for decreasing charge recombination. As a result, PSC using a ∼4 nm Parylene C layer exhibits a remarkably increased open-circuit and fill factor and a substantially enhanced efficiency of 21.7 % from pristine 19.4 %. Moreover, the Parylene C-based PSCs have attained long-term thermal and operational stabilities with good reproducibility. Without encapsulation, the degradation was limited to 11 % after 500 h of aging under ambient atmosphere/dark, 85 °C/N2, or constant illumination/ N2 conditions. This work lays a solid foundation for further stability by CVD interface modification.
Abstract
The performance of perovskite solar cells (PSCs) is negatively affected by iodine (I
2
) impurities generated from the oxidation of iodide ions in the perovskite precursor powder, solution, ...and perovskite films. In this study, the use of potassium formate (HCOOK) as a reductant to minimize the presence of detrimental I
2
impurities is presented. It is demonstrated that HCOOK can effectively reduce I
2
back to I
−
in the precursor solution as well as in the devices under external conditions. Furthermore, the introduced formate anion (HCOO
−
) and alkali metal cation (K
+
) can reduce the defect density within the perovskite film by modulating perovskite growth and passivating electronic defects, significantly prolonging the carrier lifetime and reducing the
J–V
hysteresis. Consequently, the maximum efficiency of the HCOOK‐doped planar n–i–p PSCs reaches 23.8%. After 1000 h of operation at maximum power point tracking under continuous 1 sun illumination, the corresponding encapsulated devices retain 94% of their initial efficiency.
