Efficient regulation of active layer morphology and interfacial charge-transfer process by porphyrin-based additive in organic solar cells

Active layer morphology and interfacial charge-transfer (CT) properties in organic solar cells (OSCs) greatly affect device performance but are difficult to control. Here, a porphyrin derivative meso- tetrakis(3,5-bis (trifluoromethyl)phenyl)porphyrin (TBTPP) is applied as additive in OSCs to tune the morphology and interfacial CT process of donor PM6 and acceptor Y6 blend. In combination with molecular dynamics (MD), density functional theory (DFT), and time-dependent DFT (TD-DFT), we systematically investigate the active layer morphology and interfacial properties of PM6/Y6 and PM6/Y6/TBTPP. The theoretical calculations confirm that TBTPP can significantly regulate active layer morphology and interfacial CT characteristics. The results decipher that blend PM6/Y6/TBTPP features much stronger intermolecular interactions than PM6/Y6 and more phase separation interfaces. Moreover, after adding TBTPP, the percentage of CT states increases from 53% to 73%, and the net charge-transferred amount of almost all CT states enlarges. Under the TBTPP-addition condition, the charge separation degree of 60% excitons is improved. This research demonstrates that the introduction of TBTPP is of great significance for developing high-performance OSCs because it possesses the dual efficacy of regulating morphology and simultaneously improving CT properties.