D-A-π-A-D-type Dopant-free Hole Transport Material for Low-Cost, Efficient, and Stable Perovskite Solar Cells

The development of low-cost and efficient hole transport materials (HTMs) is important for the commercialization of perovskite solar cells (PSCs). Comparing with the widely studied D-A-D and D-π-D linear-type small molecule HTMs, DTB-FL with a D-A-π-A-D molecular design is proposed, featuring facile synthesis and excellent opto-electronic properties. Moreover, the HTM with efficient surface passivation effects and proper energy level alignment at the hole extraction interface effectively inhibits recombination loss and improves the charge collection property.  As a result, the champion efficiencies of 21.5% and 19.6% for active areas of 0.09 and 1.0 cm², respectively, with superior operational stability are achieved by using DTB-FL HTM. In addition, DTB-FL can also be used as efficient HTM for all-inorganic PSCs, producing an impressive PCE of 17.0%with a high V_oc of 1.30 V. These results underscore the promising potential of the D-A-π-A-D molecular design in preparing low-cost dopant-free HTMs toward stable and efficient PSCs.