High Open Circuit Voltage for Perovskite Solar Cells with S,Si-Heteropentacene-Based Hole Conductors

High photovoltage in perovskite solar cells (PSCs) can be achieved by designing new hole transporting materials (HTMs) with relatively deeper energy levels of the highest occupied molecular orbital (HOMO). Here, we report on the synthesis of a new heteroacene-based HTM (HTM-1) and demonstrate its potential in the fabrication of FAPbBr(3) [FA = CH(NH2)(2)] PSCs yielding V-OC as high as 1.55 V, a record value for this light harvester. The energetic position of the frontier orbitals of HTM-1 was estimated using electrochemical measurements, and the charge transport across the interfaces was studied using steady-state and time-resolved photoluminescence. When spiro-OMeTAD (HOMO = -5.1 eV) is replaced with HTM-1 (HOMO = -5.3 eV), the V-OC increases from 1.51 to 1.55 V, whereas the J(SC) value decreases from 7.0 to 5.7 mA cm(-2). The similar trade-off between J(SC) and V-OC is observed for efficient iodide-based PSCs, suggesting that there is a critical energy level for the HOMO below which overall photovoltaic performance will suffer. After probing at a maximum power point under full-sun illumination at 60 degrees C for a duration of 120 h, the FAPbBr(3) PSCs based on HTM-1 retained approximate to 95 % of their initial efficiency, which demonstrates their robust operational stability.