Dicyanovinylene and Thiazolo[5,4‑d]thiazole Core Containing D–A–D Type Hole-Transporting Materials for Spiro-OMeTAD-Free Perovskite Solar Cell Applications with Superior Atmospheric Stability

In perovskite solar cell (PSC) devices, hole-transporting materials (HTMs) are vital components affecting the charge separation and playing an important role in achieving high efficiencies. These may also protect active light-absorbing layers from degradation. The current best-in-class HTM Spiro-OMeTAD is prohibitively expensive for large-scale applications, and hence, design of novel cost-effective HTMs yielding comparable device performance is essential. In this paper, we report synthesis of donor–acceptor–donor (D–A–D) type hole-transporting materials (TTz-1 and TPDCN) featuring the dicyanovinylene and thiazolo­[5,4-d]­thiazole cores and evaluate their performance via integrating them in perovskite solar cells (PSCs). The results suggest that both the HTMs are easy to synthesize and demonstrate favorable structural characteristics for device integration. Detailed analysis reveals that the molecules show appropriate energy level alignment with methylammonium lead iodide (CH₃NH₃PbI₃) perovskite and possess good thermal stability and high hole mobility. Planar PSC devices fabricated using TTz-1 as an HTM yielded a power conversion efficiency (PCE) of 11.37%, while devices using TPDCN show a PCE of 10.11%, comparable to the PCE of 11.62% obtained in control samples based on Spiro-OMeTAD. In addition, stability analysis of the devices shows that devices fabricated using TTz-1 and TPDCN exhibit superior atmospheric stability as compared to those based on Spiro-OMeTAD. These results suggest that the reported HTM architectures are promising leads for designing new HTMs for perovskite solar cells owing to their simple and scalable synthesis and tunability.