Polycrystalline Polymer Donor as Pre-Aggregate Toward Ordered Molecular Aggregation for 19.3% Efficiency Binary Organic Solar Cells.

Organic semiconductors are generally featured with low structure order in solid state films, which leads to low charge transport mobility and strong charge recombination in their photovoltaic devices. In this work, we report a "polycrystal-induced aggregation" strategy to order the polymer donor (PM6) and non-fullerene acceptor (L8-BO) molecules during solution casting with the assistance of PM6 polycrystals that were incubated through a vapor diffusion method, toward improved solar cell efficiency with either thin or thick photoactive layers. These PM6 polycrystals were redissolved in chloroform to prepare PM6 pre-aggregates (PM6-PA), and further incorporated into the conventional PM6:L8-BO blend solutions, which was found to prolong the molecular organization process and enhance the aggregation of both PM6 and L8-BO components. As the results, with the assistance of 10% PM6-PA, PM6:L8-BO solar cell devices obtained power conversion efficiencies (PCEs) from 18.0% and 16.2% to 19.3% and 17.2% with a 100 and 300 nm -thick photoactive layer respectively. This article is protected by copyright. All rights reserved.