Efficient wide-bandgap perovskite photovoltaics with homogeneous halogen-phase distribution

Wide-bandgap (WBG) perovskite solar cells (PSCs) are employed as top cells of tandem cells to exceed single-junction efficiency limits, but they exhibit severe open-circuit voltage (VOC) loss with increasing bromine content. Here we identify inhomogeneous halogen-phase distribution during film formation as the root cause hindering efficient carrier extraction. We propose forming a homogeneous halogen-phase distribution via a double-layer structure (D-2P) based on 2-(9H-carbazol-9-yl)ethyl phosphonic acid that provides nucleation sites for perovskite crystallization. Density functional theory (DFT) shows D-2P reduces formation energies of both Br- and I-based phases and enables bottom-up templated crystallization. The homogeneous perovskite phase improves carrier extraction and reduces Shockley-Read-Hall recombination, yielding a high VOC of 1.32 V. A D-2P-treated WBG device (1.75 eV) achieves a record PCE of 20.80% (certified 20.70%), the highest reported for WBG (>1.74 eV) PSCs.

Rui Wang, Xiaoyu Liu, Shan Yan, Ni Meng, Xinmin Zhao, Yu Chen, Hongxiang Li, Saif M. H. Qaid, Shaopeng Yang, Mingjian Yuan, Tingwei He