Asymmetric Conjugated Molecule Co-Deposition for High-Performance HTL-Free Carbon-Based Perovskite Solar Cells

Planar hole-transport-layer (HTL)-free carbon-based perovskite solar cells (C-PSCs) show great promise due to their chemical stability and cost-effectiveness. However, the power conversion efficiency (PCE) of HTL-free C-PSCs remains limited by severe interfacial nonradiative recombination and inefficient charge extraction. Herein, we designed an asymmetric D-A-D'-A' conjugated molecule 2BCz-BD and employed a co-deposition strategy by incorporating 2BCz-BD into the perovskite precursor solution during film fabrication. The coordination ability of 2BCz-BD regulates perovskite crystallization and passivates surface defects, thereby suppressing interfacial non-radiative recombination. The favored p-type semiconducting characters also optimize energy-level alignment to enhance charge extraction. Additionally, the large dipole moment of 2BCz-BD induces an ordered orientation on the perovskite surface, serving as a template for controlled carbon electrode deposition and enabling high-quality electrode fabrication. As a result, small-area (0.062 cm²) and large-area (1.004 cm²) devices achieved remarkable PCEs of 23.24% and 22.09%, respectively. The unencapsulated devices retained over 90.4% of their initial PCE after 3100 h of operation.