Energy Transfer Induced by TADF Polymer Enables the Recycling of Excitons in Perovskite Solar Cells
Yuanyuan Meng, Jiasen Zhang, Chang Liu, Kanghui Zheng, Lisha Xie, Shixiao Bu, Bin Han, Ruikun Cao, Xu Yin, Cuirong Liu, Ziyi Ge
Abstract
Abstract Formamidinium lead triiodide (FAPbI 3 ) has been demonstrated as the most efficient perovskite system to date, due to its excellent thermal stability and an ideal bandgap approaching the Shockley‐Queisser limit. Whereas, there are intrinsic quantum confinement effects in FAPbI 3 , which lead to unwanted non‐radiative recombination. Additionally, the black α‐phase of FAPbI 3 is unstable under room temperature due to the significant residual tensile stress in the film. To simultaneously address the above issues, a thermally‐activated delayed fluorescence polymer P1 is designed in the study to modify the FAPbI 3 film. Owing to the spectral overlap between the photoluminescence of P1 and absorption of the above‐bandgap quantum wells of FAPbI 3 , the Förster energy transfer occurs at the P1/FAPbI 3 interface, which further triggers the Dexter energy transfer within FAPbI 3 . The exciton “recycling” can thus be realized, which reduces the non‐radiative recombination losses in perovskite solar cells (PSCs). Moreover, P1 is found to introduce compressive stress into FAPbI 3 , which relieves the tensile stress in perovskite. Consequently, the PSCs with P1 treatment achieve an outstanding power conversion efficiency (PCE) of 23.51%. Moreover, with the alleviation of stress in the perovskite film, flexible PSCs (f‐PSCs) also deliver a high PCE of 21.40%.