Optimising 2D Formamidinium Perovskites for Stable and Efficient Solar Cells

Perovskite solar cells (PSCs) have made remarkable strides in achieving high power conversion efficiency, but their commercialization is still challenged by stability issues. Formamidinium (FA)-based two-dimensional (2D) perovskites have emerged as highly promising candidates due to the outstanding optoelectronic characteristics exhibited by inherent FA-based perovskites and enhanced environmental stability provided by 2D structures. The efficiency and stability of FA-based 2D PSCs are still relatively low.

In the first work using one-step deposition method. We tuned the Pb-I octahedral twisting and lattice distortion by organic spacer cation engineering to stabilise the FA-based 2D perovskite lattice. We further modulated the crystallization kinetics with a molecular-type Selenourea (SU) additive to inhibit the in-plane growth of quantum wells in 2D perovskites. The optimized FA-based 2D PSCs achieved a record-high power conversion efficiency (PCE) of 20.03% and exhibited less than 1% efficiency degradation after operating at maximum power point for 1000 hours.[1]

In the second work, we developed an additive-stabilized spacer-cation-preponed two-step deposition method to achieve the out-of-plane orientation and grain sizes larger than 5 µm in 2D perovskites. The optimized 2D PSCs achieved a high PCE of 21.16% and a short-circuit current of 23.71 mA cm⁻², among the highest in 2D PSCs. The PSCs demonstrate remarkable stability, with a PCE decrease of less than 5% after exposure to 65±10% humidity for 1100 hours, operation at 85°C for 1077 hours, or continuous illumination for 1045 hours.[2]

References
[1]. Zeng, Kong, Liang, Li, Lvtao, Su, Wang, Peng, Ye, Chen, Gao, Huang, Zheng, and Yang, Advanced Materials  35, 2306051, 2023.
[2]. Zeng, Su, Kong, Li, Liang, Zhang, Wang, Zhang, Lvtao, Liu, Gao, Huang, Yang, and Zheng, Energy & Environmental Science 17, 8284 2024.