Additive engineering for high-performance P3HT:non-fused ring electron acceptor organic solar cell

In this study, we address the challenge of improving the power conversion efficiency (PCE) of P3HT-based organic solar cells (OSCs) by modulating the phase separation morphology. We synthesize a non-fused ring electron acceptor (NFREA), MOT, with an ultra-narrow bandgap and absorption up to 1000 nm, and pair it with P3HT to prepare OSCs. We find that solvent additives with similar structures can induce different phase separation and morphology in the P3HT:MOT blend, leading to distinct exciton dissociation and device performance. Among the additives tested, 1-methoxynaphthalene (1-MN) induces better phase separation of P3HT:MOT blend, resulting in a PCE of 6.98%, which is higher than that of devices processed with 1-chloronaphthalene (1-CN) and 1-phenylnaphthalene (1-PN) additives. Detailed photoelectric properties and exciton dissociation process analysis indicate that the higher performance processed by 1-MN is attributed to the preferable morphology induced by the phase separation. Our work not only reports a new NFREA to pair with P3HT but also develops a simple additive engineering strategy for regulating the morphology in P3HT-based OSCs.