Inter-diffused ordered bulk heterojunction organic photovoltaics: optimized morphology for efficient exciton dissociation and charge transport

Effective control of the morphology can enhance the performance of organic photovoltaics. The morphology of an active layer needs to have a large interfacial area between donors and acceptors for efficient exciton dissociation and continuous, direct charge transport paths to electrodes for high charge transport efficiency. These two requirements are usually contradictory. Here, we propose a morphology that meets these requirements nearly simultaneously, called an inter-diffused ordered bulk heterojunction (IDOBHJ). This novel structure exhibited 9% higher performance based on the Monte Carlo simulation than an optimized disordered bulk heterojunction. The main reasons for superior performance were attributed to the comparable short circuit current density and a higher fill factor. We also implemented the IDOBHJ morphology by the experimental nanoimprint technique combined with thermal annealing process to confirm simulation results. Our experimental results are indeed consistent with the theoretical analysis.