Optimized bicontinuous interpenetrating network morphology formed by gradual chlorination to boost photovoltaic performance

Bicontinuous interpenetrating network morphology formed spontaneously in a bulk-heterojunction (BHJ) photoactive layer is highly desirable for organic solar cells (OSCs). Herein, we report the synthesis of a series of chlorine-free and chlorinated polymer donors, PBDP-H, PBDP-Cl and PBDP-2Cl to systematically investigate the relationships between molecular structure, morphology, and photovoltaic performance after the gradual introduction of Cl atoms. We developed a fully evolved nanoscale bicontinuous interpenetrating network morphology from PBDP-H:BTIC-BO-4Cl to PBDP-Cl:BTIC-BO-4Cl to PBDP-2Cl:BTIC-BO-4Cl as active layer blend films. Benefiting from the favorable morphology, PBDP-2Cl based organic solar cell devices were found to exhibit efficient exciton separation, faster charge transport property, more balanced charge mobilities and suppressive bimolecular recombination. An outstanding power conversion efficiency (PCE) of 13.34% with enhanced synchronous V-OC, J(SC) and FF is achieved in PBDP-2Cl:BTIC-BO-4Cl-based OCS devices, which is much higher than that of PBDP-Cl (9.84%) and PBDP-H (6.66%) based devices. These results indicate that the favorable nanoscale bicontinuous interpenetrating network morphology can be precisely manipulated by a gradual chlorination strategy to enhance photovoltaic performance.