Role of interface properties in organic solar cells: from substrate engineering to bulk-heterojunction interfacial morphology

The performance of organic solar cells (OSCs) depends on a fine, carefully optimized bulk-heterojunction (BHJ) microstructure. The understanding and manipulation of BHJ morphology have been the focus of research in optoelectronic devices. In this article, recent advances in understanding and controlling the BHJ morphologyviasubstrate engineering and BHJ active layer processing are reviewed. From the chemical and physical surface structure of substrates, we reviewed the active layer morphology depending on the nature of the substrate and the deposition conditions, and it can also be controlled to change the blend-substrate interface by changing the surface properties of the substrate. We also reviewed the effect of solvent (co-solvent and solvent additive) and post-treatment (thermal annealing and solvent vapor annealing) on the evolution kinetics of the film, which helps to form the optimal percolation path and thus provides a simple way to improve photovoltaic performance. Since the interaction between intermolecules is weak, the sensitive assembly of molecules depends on fining miscibility between the components in the BHJ active layer. Starting from the processing conditions of the substrate and the active layer can greatly control the morphology of BHJ, and provide future research directions for OSCs.