Rational Organic Subcell Engineering Enables Efficient Organic-Perovskite Tandem Solar Cells
Wenxu Liu, Yuxin Duan, Zhewei Zhang, Jiaxin Gao, Shaoxian Li, Zachary Fink, Xuefei Wu, Zaifei Ma, Akinori Saeki, Thomas P. Russell, Yao Liu
Abstract
Organic subcells are an essential component of organic-perovskite tandem solar cells, yet current choices are limited to those with low open-circuit voltages ( V OC s) and efficiencies. By designing and synthesizing benzo[d][1,2,3]triazole-substituted acceptors, LBz-F and LBz-Cl, which exhibit shallower frontier orbital energy levels and narrower optical bandgaps than the typical nonfullerene acceptor L8-BO, we overcome this limitation. LBz-F and LBz-Cl can form alloys with L8-BO in the active layer, broadening the absorption, optimizing charge carrier dynamics, and reducing energy losses of the devices, which results in improved short-circuit currents and fill factors without compromising a high V OC in the organic subcell. By combining PM6:L8-BO:LBz-F as the back cell with a wide bandgap (1.72 eV) perovskite front cell, efficiencies of 22.11% and 20.18% with high V OC s approaching 2.1 V are achieved for small and large area tandem devices, respectively, highlighting the effectiveness of rational organic subcell engineering for efficient, large-area organic-perovskite tandem solar cells.