Advances in Side‐Chain Engineering of Triarylamine and Thienyl‐Based Hole Transport Materials for Perovskite Solar Cells

Recent advancements in perovskite solar cells (PSCs) have marked a transformative milestone in photovoltaics, offering innovative and cost‐effective solutions for efficient energy generation. However, challenges related to stability have impeded their commercialization. To address these challenges, researchers have focused on approaches like interfacial and structural engineering, particularly in the development of efficient hole transport materials (HTMs). Additionally, side‐chain engineering of HTMs plays a key role in improving hole mobility and stability, further boosting the overall performance of PSCs. This review highlights how side‐chain engineering in triarylamine‐based HTMs and thienyl derivatives enhance π–π stacking, resulting in deeper highest occupied molecular orbital (HOMO) energy levels and improved intermolecular interactions. Triarylamine‐based HTMs with electron‐donating substituents show improved interfacial interactions with the perovskite (PVK) absorber, passivating defects and reducing recombination losses. Similarly, polymeric thienyl derivatives with optimized supramolecular ordering demonstrate enhanced charge mobility and stability due to rigid polymer stacking. The incorporation of fluorine and sulfur‐enriched molecules in the structure broadens light absorption spectra. Moreover, fine‐tuning molecular weight and modifying donor–π–acceptor architectures significantly enhance mechanical, electrical, and optical properties. This review provides insights into developing novel HTMs through side‐chain engineering to overcome stability issues and accelerate the commercialization of PSCs.