Self-assembled hole-selective contact for efficient Sn-Pb perovskite solar cells and all-perovskite tandems
Jingwei Zhu, Xiaozhen Huang, Yi Luo, Wenbo Jiao, Yuliang Xu, Juncheng Wang, Zhiyu Gao, Kun Wei, Tianshu Ma, Jiayu You, Jialun Jin, Shenghan Wu, Zhihao Zhang, Wenqing Liang, Yang Wang, Shengqiang Ren, Changlei Wang, Cong Chen, Jinbao Zhang, Dewei Zhao
Abstract
Self-assembled monolayers (SAMs) have displayed unpredictable potential in efficient perovskite solar cells (PSCs). Yet most of SAMs are largely suitable for pure Pb-based devices, precisely developing promising hole-selective contacts (HSCs) for Sn-based PSCs and exploring the underlying general mechanism are fundamentally desired. Here, based on the prototypical donor-acceptor SAM MPA-BT-BA (BT), oligoether side chains with different length (i.e., methoxy, 2-methoxyethoxy, 2-(2-methoxyethoxy)ethoxy group) were custom-introduced on the benzothiadiazole unit to produce the target SAMs with acronyms MPA-MBT-BA (MBT), MPA-EBT-BA (EBT), and MPA-MEBT-BA (MEBT), respectively, and acting as HSCs for efficient Sn-Pb PSCs and all-perovskite tandems. The introduction of oligoether side chains enables HSCs effectively accelerate hole extraction, regulate the crystal growth and passivate surface defects of Sn-Pb perovskites. In particular, benefiting from the enhanced Sn-Pb perovskite film quality and the suppressed interfacial non-radiative recombination losses, EBT-tailored LBG devices yield a champion efficiency of 23.54%, enabling 28.61% efficient monolithic all-perovskite tandems with an impressive VOC of 2.155 V and excellent operational stability as well as 28.22%-efficiency 4-T tandems. The development of hole-selective contacts for Sn-based perovskite solar cells is highly desirable. Here, the authors report self-assembled monolayers with oligoether side chains on the benzothiadiazole unit and achieve an efficiency of 28.61% for operationally stable all-perovskite tandems.