Intensification of Vertical Phase Separation for Efficient Polymer Solar Cell via Piecewise Spray Assisted by a Solvent Driving Force

Piecewise spray has the advantage of controlling the component distribution, i.e., constructing vertical phase-separated active layers, to improve the charge generation efficiency of large-scale polymer solar cells. However, it brings a connection problem because of the drastic difference in the donor/acceptor ratio of continuous coatings using the conventional solvent. Assisted by 1,3,5-trimethylbenzene-based solvent engineering, a solvent driving force is formed, resulting in a continuous interface for piecewise spray-coated active layers. The blend film forms a bicontinuous interpenetrating network in the active layer and provides efficient percolation pathways for charge carrier transport, resulting in a considerable improvement in the photovoltaic performance. When the donor/acceptor ratio is 1:2 in the first coating and 2:1 in the second coating, and the thickness of each coating is 90 nm, the performance of the PBDB-T-2Cl:IT4F photovoltaic device shows a notable conversion efficiency of 12.29% with a high short-circuit current density of 21.55 mA cm(-2). Importantly, this piecewise spray technique can be used for large-scale module fabrication.