Hole-Transporting Materials Incorporating Carbazole into Spiro-Core for Highly Efficient Perovskite Solar Cells

Hole-transporting materials (HTMs) play a significant role in hole transport and extraction for perovskite solar cells (PeSCs). As an important type of HTMs, the spiro-architecture-based material is widely used as small organic HTM in PeSCs with good photovoltaic performances. The skeletal modification of spiro-based HTMs is a critical way of modifying energy level and hole mobility. Thus, many spiro alternatives are developed to optimize the spiro-type HTMs. Herein, a novel carbazole-based single-spiro-HTM named SCZF-5 is designed and prepared for efficient PeSCs. In addition, another single-spiro HTM SAF-5 with reported 10-phenyl-10H-spiro[acridine-9,9 '-fluorene] (SAF) core is also synthesized for comparison. Through varying from SAF core to SCZF core as well as comparing with the classic 9,9 '-spiro-bifluorene, it is found that the new HTM SCZF-5 exhibits more impressive power conversion efficiency (PCE) of 20.10% than SAF-5 (13.93%) and the commercial HTM spiro-OMeTAD (19.11%). On the other hand, the SCZF-5-based device also has better durability in lifetime testing, indicating the newly designed SCZF by integrating carbazole into the spiro concept has good potential for developing effective HTMs.