Customizing a Coordinative Crab Molecule BCP-3N with Multifunctionality for High-Performance Inverted Perovskite Solar Cells

Defects at the perovskite grain boundaries and the interfaces between perovskite and charge transport layers in perovskite solar cells (PSCs) are a curse of nonradiative recombination losses and device degradation channels. Herein, the custom design and synthesis of a multifunctional small molecule (N ²,N ⁹-bis(3-(dimethylamino)propyl)-4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxamide (BCP-3N) featured by the π-conjugated phenanthroline and an array of lone-pair electron donor atoms from the carbonyl and amine groups are reported. The BCP-3N is used as a Lewis base to multidentate passivate the undercoordinated Pb²⁺ ions forming an ultrathin tunnel layer, in synergy with ethanol as a green antisolvent to simultaneously orient the growth of perovskite, resulting in a significantly reduced defect density in perovskite films. With BCP-3N, a significant increase in open-circuit voltage (V _oc = 1.12 V) is achieved of inverted (p–i–n structure) PSCs, along with a record power conversion efficiency of ≈21% among alcohol antisolvent processed cells. Also, attested are a much higher illumination and humidity stability of the BCP-3N-based device. Combined experimental and theoretical studies have uncovered the multifunctional roles of BCP-3N in stabilizing high-quality Cs–FA–MA triple-cation mixed perovskites under light, bias, and humidity stresses, enlightening the molecular design for PSCs.