Facilely Synthesized spiro[fluorene-9,9′-phenanthren-10′-one] in Donor–Acceptor–Donor Hole-Transporting Materials for Perovskite Solar Cells

We have demonstrated two novel donor–acceptor–donor (D–A–D) hole-transport material (HTM) with spiro[fluorene-9,9′-phenanthren-10′-one] as the core structure, which can be synthesized through a low-cost process in high yield. Compared to the incorporation of the conventional HTM of commonly used 2,2′,7,7′-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (Spiro-OMeTAD), the synthesis process is greatly simplified for the presented D–A–D materials, including a minimum number of purification processes. This results in an increased production yield (>55 %) and suppressed production cost (<30 $ g⁻¹), in addition to high power conversion efficiency (PCE) in perovskite solar cells (PSCs). The PCE of a PSC using our D–A–D HTM reaches 16.06 %, similar to that of Spiro-OMeTAD (16.08 %), which is attributed to comparable hole mobility and charge-transfer efficiency. D–A–D HTMs also provide better moisture resistivity to prolong the lifetime of PSCs under ambient conditions relative to their Spiro-OMeTAD counterparts. The proposed new type of D–A–D HTM has shown promising performance as an alternative HTM for PSCs and can be synthesized with high production throughput.