Homogenizing hole-selective contacts for centimeter-square flexible perovskite/Cu(In,Ga)Se <sub>2</sub> tandems
Jingjing Zhou, Enbing Bi, Weizhong Tian, Shaochen Zhang, Caner Değer, İlhan Yavuz, Jiahui Shen, Libing Yao, Xuechun Sun, Jichuang Shen, Ke Zhao, Runda Li, Jiazhe Xu, Qingqing Liu, Xiaonan Wang, Qinggui Li, Yixin Luo, Pengju Shi, X.B. Zhang, Yuan Tian, Donger Jin, Lü Jin, Sisi Wang, Jingyi Sun, Chongyan Lian, Tie Guo, Jingjing Xue, Rui Wang
Abstract
(CIGS) tandems offer a path to high-efficiency and lightweight photovoltaics. However, simultaneously achieving high efficiency and mechanical durability remains a challenge. A contributing factor is the interfacial inhomogeneity arising from molecular aggregation in planar carbazole-based hole-selective contacts (HSCs) on flexible substrates. Here, we develop a strategy of spatial steric hindrance that transforms planar carbazole core into a three-dimensional π-conjugated skeleton. This molecular reconfiguration suppresses intermolecular π-π stacking, yielding homogenized selective contacts and high-quality perovskite films. When integrated into flexible monolithic perovskite/CIGS tandem devices, this strategy enabled a champion stabilized power conversion efficiency (PCE) of 26.2% (certified 25.5%) for a 0.091-square centimeter device and 25.3% (certified 24.3%) for a centimeter-scale device, both representing high certified efficiencies reported to date for flexible two-terminal tandems. These devices demonstrated remarkable mechanical robustness, retaining their initial PCE after 10,000 bending cycles at a 10-millimeter radius, highlighting the potential of molecular-level interfacial engineering to realize high-efficiency, stable, and scalable flexible photovoltaics.