Modulation of Vertical Component Distribution for Large-Area Thick-Film Organic Solar Cells

Thick active layers in organic solar cells (OSCs) have a great promise of enhancing light absorption and providing pinhole-free films for large-scale fabrication. Since charge carriers in thick films need a longer transporting path in the vertical direction to the electrode than in thin films, modulation of the active layer morphology in thick films is highly required for effective charge transport. Herein, thin-film (approximate to 110 nm) and thick-film (approximate to 300 nm) OSCs based on a PM6:IT-4 F film are fabricated by blade coating with various additive contents. It is found that the optimized thick-film device needs more additives than the optimized thin-film device. The addition of more additives in thick-films promotes vertical component distribution and enhances the crystallization, resulting in efficient charge transport with reduced charge recombination and electron (or hole) accumulation within the thick active layer. These results are also confirmed by PM6:Y6-based devices, in which optimized thin-film and thick-film devices exhibit power conversion efficiency (PCE) of 16.69% and 14.91% at the additive contents of 0.3% and 0.6%, respectively. Encouragingly, thick-film device with 0.6% additive has a narrow distribution of PCE values, and high PCEs of 13.94% and 13.05% are obtained for the large-area (1 cm(2)) rigid and flexible thick-film OSCs, showing great application prospect.

Automated summary

The study shows that adding more additives in thick-film organic solar cells can promote charge transport and enhance crystallinity, thereby reducing charge recombination and electron (or hole) accumulation within the active layer.