Promoting Thermodynamic and Kinetic Stabilities of FA-based Perovskite by an in Situ Bilayer Structure.

Xu, Alex Fan; Liu, Na; Xie, Fanlong; Song, Tinglu; Ma, Yue; Zhang, Pengxiang; Bai, Yang; Li, Yujing et al. · Nano Lett · 2020

basic_science · Level V

Where this comes from

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 (PyPbI<sub>3</sub>), 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 PyPbI<sub>3</sub>, 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.