Increasing the stability of perovskite solar cells with dibenzofulvene-based hole transporting materials

The hole transporting material (HTM) plays a critical role in the performance and stability of perovskite solar cells (PSCs). In PSCs with n-i-p architecture, Spiro-OMeTAD has been widely applied as HTM reaching the highest efficiency, however, its low stability slows down the long-term application of the devices. Thus, in order to enhance the performance of the devices, in this work we analyse, in n-i-p PSCs, three organic hole-transporting materials containing two and three amino redox centers bridged to a dibenzofulvene (DBF) backbone. The difference in the molecular structure of the three DBF-based HTMs lies in the substitution pattern on the exocyclic fulvene bond. Methodical studies of kinetics and morphology reveal that the nature of the substituent plays a vital role in the performance of the PSC, allowing to obtain an efficiency (16.08 %) comparable to reference Spiro-OMeTAD (17.75 %). In addition, the PSCs with DBF-based HTMs demonstrated better stability against the reference prepared with Spiro-OMeTAD under continuous illumination in ambient conditions (15 ± 2°C and 60 ± 5% RH), as well as under dark and low-humidity conditions. These results place our DBF-based organic molecules as promising HTMs to form part of highly efficient and long-term stability perovskite solar cell applications.