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.