Theretofore Highest Efficiency in Vacuum-Deposited Organic Solar Cells Originating From Triarylamine-Based...

Vacuum-deposited organic solar cells (v-OSCs) are alternative candidates for photovoltaics technologies. Their advantages include well-defined molecular structures, high purity of materials, excellent batch-to-batch reproducibility, and solution-free fabrication process that enables good compatibility with underlying perovskite layer for tandem devices. Triarylamine-based small-molecule donors are commonly used in v-OSCs, however, their power conversion efficiencies (PCEs) are constrained by low short-circuit current density (J_sc). Moreover, to match with the photocurrent of perovskite subcell, enhancing J_sc of v-OSCs is highly demanded. Herein, four small-molecule donors (named PT, PF, BT, and BF) based on triarylamine electron-donating moieties are designed. Compared with linear analogues PT and PF, BT and BF with fused-ring building blocks including benzothiophene and benzofuran exhibit smaller bandgaps, lower highest occupied molecular orbital (HOMO) energy levels, and higher hole mobilities. Consequently, v-OSCs based on BT and BF exhibit surprisingly high J_sc values (17.91 and 18.13 mA cm^-2, respectively), representing the highest reported J_sc for v-OSCs. Moreover, the J_sc enhancement leads to improved PCEs of devices based on BT and BF (10.53% and 10.11%, respectively). Remarkably, the PCE of 10.53% for the BT-based device represents the best PCE reported for v-OSCs. This work opens a promising avenue to develop high-performance small-molecule donors for v-OSCs.