Abstract Commercialization is widely believed to be achievable for metal halide perovskite solar cells with high efficiency and low fabrication cost. However, stability remains a key obstacle for them to compete with established photovoltaic technologies. The photovoltaic community relies on the International Electrotechnical Commission (IEC) standard for the minimum stability assessment for any commercialized solar cell. In this review, we summarize the main degradation mechanisms of perovskite solar cells and key results for achieving sufficient stability to meet IEC standards. We also summarize limitations for evaluating solar cell stability and commercialization potential within the framework of the current IEC standard, and discuss the importance of outdoor testing. 

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Degradation pathways in perovskite solar cells and how to meet international standards

Perovskite solar cells attract widespread attention due to their impressive power conversion efficiencies, high absorption coefficients, tunable bandgap, and straightforward manufacturing protocols. However, in the process of further development and optimization toward mass production, the long‐term stability stands as one of the most urgent challenges that need to be overcome. Given the excellent thermal stability and high structural designability, ionic liquids (ILs) are relatively green room‐temperature molten salts that have been widely applied to perovskite photovoltaic devices with promising results in view of improved stability and enhanced device performance. In this review, the reasons and mechanisms of instability of such devices under external and internal factors are analyzed. The current strategies of ILs engineering for improved stability of the devices are classified and summarized, including the IL‐assisted perovskite film evolution and IL‐modified photophysical properties of the perovskite photoactive layer and the related stability and photovoltaic performance of the devices. The challenges that stand as obstacles toward further development of perovskite solar cells based on IL engineering and their prospects are also discussed.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/sstr.202200048

Recent Progress in Ionic Liquids for Stability Engineering of Perovskite Solar Cells

Metal halides have been demonstrated to be promising candidates for X-ray detectors. However, its large leakage current caused by the severe ion migration and intrinsic defect substantially degrades device performance. In this work, an asymmetric BA2CsPb2I7-CsPbI3 planar heterojunction X-ray detector is designed to suppress the leakage current. Both experimental and theoretical calculations demonstrate that: 1) enlarged ion migration energy (0.80 eV) and conductivity mutation at the interface ensure stable baseline and suppress leakage current; 2) CsPbI3 ensures effective absorption of X-ray, while BA2CsPb2I7 induces larger bulk resistance, which is expected to achieve higher photocurrent and lower dark current. Finally, the obtained X-ray detector exhibits negligible baseline drift, faster response, and smaller leakage current compared to the CsPbI3 counterparts. Specifically, the device exhibits a detection limit of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.092 ~\mu $ </tex-math></inline-formula> Gy <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{air}$ </tex-math></inline-formula> /s, and the CsPbI3-based device was <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.63 ~\mu $ </tex-math></inline-formula> Gy <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{air}$ </tex-math></inline-formula> /s. 

Asymmetric Metal Halide Film With Suppressed Leakage Current for High Sensitive X-Ray Detection and Imaging

https://doi.org/10.1016/j.jmat.2022.08.001

Thermoelectric properties of high-entropy rare-earth cobaltates

Multifunctional alkylamines enable defect passivation and energy level alignment for efficient and stable inverted CsPbI3 perovskite solar cells

Longevity is a key constraint for hybrid perovskite based photovoltaics. Here it is demonstrated that ion migration‐induced degradation can be eliminated by incorporation of multifunctional poly(ionic‐liquid)s (PILs) additives, resulting in ultrastable perovskite solar cells (PVSCs). The presence of PILs suffices to construct an “ionic polymer network,” providing the functionalities of defect passivation and ion immobilization by concurrently forming a physical barrier and chemical bonding. Compared with the defect passivation effect for the imidazolium‐based PIL (PIL‐Im) case, the quaternary ammonium‐based PIL (PIL‐Am) shows a higher interaction energy with the perovskite due to the stronger electronic coupling ascribed to the additional complexation, which endows the corresponding perovskite with higher migration energy for iodide ions. As a result, the power conversion efficiency (PCE) of anion‐cation‐mixed hybrid n‐i‐p PVSCs with PIL‐Am is remarkably improved from 20.26% to 22.22%. Specifically, the PILs‐modified device perfectly retains its dark current characteristics upon a cooling (−40 °C)–heating (85 °C) process. The unencapsulated PIL‐Am stabilized PVSC maintains 80% of the initial PCE under AM 1.5G light soaking for nearly 1500 h. The corresponding device also displays pronounced stability under thermal stress or realistic operation conditions.

Uncovering the Mechanism of Poly(ionic‐liquid)s Multiple Inhibition of Ion Migration for Efficient and Stable Perovskite Solar Cells

In this work, a novel high-entropy n -type thermoelectric material Sr 0.9 La 0.1 (Zr 0.25 Sn 0.25 Ti 0.25 Hf 0.25 )O 3 with pure perovskite phase was prepared using a conventional solid state processing route. The results of TEM and XPS show that various types of crystal defects and lattice distortions, such as oxygen vacancies, edge dislocations, in-phase rotations of octahedron and antiparallel cation displacements coexist in this high-entropy ceramic. At 873 K, the high-entropy ceramics showed both a low thermal conductivity (1.89 W/m/K) and a high Seebeck coefficient (393 μV/K). This work highlights a way to obtain high-performance perovskite-type oxide thermoelectric materials through high-entropy composition design. 

A novel high-entropy perovskite ceramics Sr0.9La0.1(Zr0.25Sn0.25Ti0.25Hf0.25)O3 with low thermal conductivity and high Seebeck coefficient

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Lingyun Gong

Papers

Uncovering the Mechanism of Poly(ionic‐liquid)s Multiple Inhibition of Ion Migration for Efficient and Stable Perovskite Solar Cells

A novel high-entropy perovskite ceramics Sr0.9La0.1(Zr0.25Sn0.25Ti0.25Hf0.25)O3 with low thermal conductivity and high Seebeck coefficient

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual Triplet Sensitization Strategy for Efficient and Stable Triplet-Triplet Annihilation Up-Conversion Perovskite Solar Cells

Effect of La3+, Ag+ and Bi3+ doping on thermoelectric properties of SrTiO3: First-principles investigation