Since the utilization of clean energy is the cornerstone of social sustainable development, the harvest of solar energy has received extensive attention. Among all the light harvesting devices, perovskite solar cells (PSC) stand out in the photovoltaic field due to their good photovoltaic properties, low cost, and easy processing. After decades of efforts, the power conversion efficiency of PSC has reached the standard of commercialization. At present, the main obstacle to its further development is the unsatisfactory stability under external stress.
Recently, Prof. ZHOU Huiqiong's research group from National Center for Nanoscience and Technology (NCSNT) of the Chinese Academy of Sciences (CAS) has developed a strain relaxation strategy to study the effect of residual strain on properties of quasi-two-dimensional (2D) perovskites. The related research results were published online in Angew. Chem. Int. Ed.
The introduction of hydrophobic spacer cations makes quasi-2D perovskites more stable compared to traditional 3D perovskites, but the stability of perovskite remains unsatisfactory. Residual strain is closely related to the crystallographic properties, which in turn can significantly affect the photovoltaic properties and stability of perovskites. The residual strain in quasi-2D perovskite with mixed spacer cations is investigated by X-ray diffraction and AFM. It’s found that there is severe tensile strain along the out-of-plane direction in pristine perovskite film, leading to poor crystallinity and insufficient stability issue. With appropriate composition of spacer cations, the tensile strain is effectively released. In addition, the XRD peaks shift and peak of the GIWAXS integral curve shift indicates the decreased lattice constant, which confirms the release of tensile strain. Benefiting from the released tensile strain, the crystallinity and carrier dynamics are improved, resulting in enhanced device performance and, more importantly, the increased stability under maximum power point tracking, 85℃, 85 relative humidity and temperature cycling between 85℃ and -40℃. In summary, optimizing the spacer cations could regulate the residual strain in quasi-2D perovskite, further improving the intrinsic stability of perovskites. This work provides a feasible strategy for further regulating the photovoltaic properties and improving the stability of perovskite-based photovoltaic devices.
CHENG Qian is the first author of the current work and Prof. ZHOU Huiqiong is the corresponding author. This work is financially supported by National Key Research and Development Program of China, the National Natural Science Foundation of China, the CAS Instrument Development Project and the Strategic Priority Research Program of Chinese Academy of Sciences.
Figure. Schematic illustration of strain relaxation in quasi-2D perovskite. (Imaged by CHENG et al.)
National Center for Nanoscience and Technology (NCNST)