Promoting Thermodynamic and Kinetic Stabilities of FA-based Perovskite by an in Situ Bilayer Structure
Fan Xu, Na Liu, Fanlong Xie, Tinglu Song, Yue Ma, Pengxiang Zhang, Yang Bai, Yujing Li, Qi Chen, Gu Xu
Abstract
The commonly employed formamidinium (FA)-containing perovskite solar cells (PSCs) exhibit a severe phase instability problem, thereby limiting their commercial applications. Here, both phase stability and energy efficiency of FA-based PSCs were improved by treating the perovskite surface with pyrrolidinium hydroiodide (PyI) salts, resulting in a 1D perovskite structure (PyPbI3), stacked on the original 3D perovskite. By employing in situ XRD measurements, we revealed that the temperature-dependent phase transition activation barrier was enhanced after forming the 1D/3D structure, resulting in a prolonged transition time by 30–40-fold. From the first-principle calculations, we found the thermodynamic energy difference between two phases reduced from −0.16 to −0.04 eV after the stacking of 1D PyPbI3, offering additional lifetime improvement. Moreover, the champion 1D/3D bilayer PSC exhibits a boosted power conversion efficiency of 19.62%, versus 18.21% of the control. Such 1D/3D bilayer structure may be employed in PSCs to enhance their phase stability and photovoltaic performance.