Design and evaluation of hole transporting molecules for flexible perovskite solar cells: Enhancing efficiency and...

Flexible perovskite solar cells (PSCs) are emerging as a promising photovoltaic technology for portable and wearable electronics, offering excellent power conversion efficiencies (PCEs) and ease of processing. In this work, we present five newly designed foldable hole transport materials (HTMs), labeled C1M1-C1M5, engineered by thiophene-bridged acceptor modifications of the reference CM molecule. Using density functional theory (DFT), we explore the structural, electronic, optical, and photovoltaic properties of these molecules. The results show that the newly designed HTMs exhibit narrow band gaps (1.65-2.32 eV), significantly lower than the CM reference (3.75 eV). Notably, the extended conjugation length of the molecules contributes to their red-shifted absorption (up to 832 nm), enhanced dipole moments (ranging from 6.37 to 19.14 D), and improved exciton dissociation, particularly for C1M5, with an exciton binding energy of 0.22 eV. Furthermore, the charge transport characteristics were found to be promising, with C1M4 exhibiting the highest charge transmission (λe = 0.036577, λh = 0.050162), where electron transport was slightly more favorable than hole transport. In conclusion, these newly engineered HTMs are highly promising for next-generation solar devices due to their excellent solution processability, efficient light harvesting, and charge transport capabilities.