Mitigating Coffee Ring Effects for Efficient Upscaling of Flexible Organic Solar Cells

Abstract

As a roll‐to‐roll compatible technology, slot‐die coating has shown great potential for manufacturing industrial‐level organic solar cells (OSCs). However, in the slot‐die coatings process, coffee rings are often formed due to the slow film‐forming kinetics, leading to a significant loss of power conversion efficiency (PCE) in upscaling device area. Herein, the coffee rings are suppressed by introducing an airflow‐assisted slot‐die technique to obtain a suitable active layer morphology with improved flatness and homogeneity. Synergistically, optimization of airflow and substrate temperature conditions, the PCE of 1 cm2 flexible OSC devices reaches 13.69%. Moreover, large‐area flexible OSC modules with 30 cm2 achieve a PCE of 13.08%, maintaining 95% of 1 cm2 device, which is the minimum PCE loss from 1 cm2 to large‐area devices. Morphology characterization shows that airflow can suppress excessive molecular aggregation and obtain suitable phase separation. Therefore, this work provides an efficient method to fabricate high‐efficiency flexible large‐area OSC modules, which will promote OSC devices from lab to fab.