Low‐Cost Perovskite Solar Cells Employing Dimethoxydiphenylamine‐Substituted Bistricyclic Aromatic Enes as Hole Transport Materials

The synthesis, characterization and photovoltaic performance of series of novel molecular hole transport materials (HTMs) based on bistricyclic aromatic enes (BAEs) are presented. The new derivatives were obtained following a simple and straightforward procedure from inexpensive starting reagents mimicking the synthetically challenging 9,9'-spirobifluorene moiety of the well-studied spiro-OMeTAD. The novel HTMs were tested in mixed cations and anions perovskite solar cells (PSCs) yielding a power conversion efficiency (PCE) of 19.2 % under standard global 100 mW cm^-2 AM1.5G illumination using 9-{2,7-bis[bis(4-methoxyphenyl)amino]-9H-fluoren-9-ylidene}-N² ,N² ,N⁷ ,N⁷ -tetrakis(4-methoxyphenyl)-9H-thioxanthene-2,7-diamine (coded as KR374). The power conversion efficiency data confirms the easily attainable heteromerous fluorenylidenethioxanthene structure as valuable core for low-cost and highly efficient HTM design and paves the way towards cost-effective PSC technology.