Dopant-Free Polymeric Hole Transport Materials with a DA'D-A Backbone for Efficient and Stable Inverted Perovskite Solar Cells

["Dopant-free hole transport layers (HTLs) play a crucial role in achieving high-efficiency and stable perovskite solar cells (PSCs). However, only a limited number of these HTLs have demonstrated power conversion efficiencies (PCEs) surpassing 21%. Herein, the design and synthesis of two polymeric HTLs with a novel DA'D-A backbone are presented. The incorporation of two A units (benzothiazole and imide functionalized aromatics) in the polymer imparts a rigid backbone, high mobility, appropriate film morphology, excellent thermal stability, and a deeper highest occupied molecular orbital energy level, crucial for achieving a more suitable energy-level alignment between HTL and perovskite layer. Notably, the champion PSC based on our HTLs exhibits a remarkable PCE of 22.02% with minimal hysteresis and excellent thermal stability, surpassing the performance of devices based on the benchmark polymeric HTL PTAA under identical conditions. These findings underscore the immense potential of our DA'D-A backbone strategy in developing high-performance dopant-free polymer HTLs for enhancing the PCE of PSCs.","Integration of benzothiazole and imide functionalized aromatics for enhanced mobility, thermal resilience, and energy level alignment is studied. An inverted perovskite solar cell exhibiting an exceptional 22.02% efficiency and excellent stability is unveiled.image (c) 2023 WILEY-VCH GmbH"]