Molecular tuning and strategic functionalization of dopant-free hole transport materials for enhanced stability and efficiency in perovskite solar cells

Abstract

The development of high-performance and stable hole transport materials (HTMs) is crucial for advancing perovskite solar cells (PSCs) toward commercialization. In this study, two novel dopant-free HTMs, denoted as SP-09 and SP-10, are designed and synthesized via a straightforward two-step C–N cross-coupling reaction. These materials incorporate strategic molecular modifications to enhance charge transport, thermal stability, and moisture resistance. Structural analysis reveals that the incorporation of methoxy (–OCH₃) into SP-09 and methylthio (–SCH₃) into SP-10 functional groups significantly modulates their electronic interactions with the perovskite layer, leading to improved energy level alignment and charge extraction efficiency, as confirmed by electrochemical and spectroscopic studies. PSCs employing SP-10 HTM demonstrate a notable enhancement in PCE to 22.1%, surpassing both SP-09 (20.8%) and the benchmark spiro-OMeTAD (20.5%). Furthermore, stability assessments under continuous illumination and ambient conditions indicate superior long-term operational durability for SP-10, retaining over 93% and 82% of its initial efficiency after 500 hours and 180 days (over 4300 hours), respectively, whereas spiro-OMeTAD suffers from substantial degradation. Notably, SP-09 and SP-10 offer a more cost-effective alternative to spiro-OMeTAD, enhancing the economic viability of PSC production. This study highlights the potential of rational molecular design in developing next-generation dopant-free HTMs, offering a viable pathway toward efficient and stable optoelectronic devices.