Multiple-Birth-Acceptor: Easily-Synthesized Mixture for Easily-Fabricated Quaternary Organic Solar Cells with Beyond 20% Efficiency.

Abstract

Ternary strategy has been proved very effective to improve the power conversion efficiency (PCE) of organic solar cells (OSCs). However, quaternary OSCs (QOSCs), containing four components in the active layer, have been rarely reported due to the complexity of material synthesis and optimization of active layer composition. Here, we developed a simple method to fabricate high-performance QOSCs by using "multiple-birth-acceptor" (MBA), a mixture of three molecules synthesized simultaneously. These A-DA'D-A type MBAs (MBA31, MBA11, MBA13, and MBA19) were synthesized by reacting one DA'D-type central segment (BTP-2CHO) with two A terminal units (γ-IC-Cl and IC-2Cl) with different feed ratios (γ-IC-Cl: IC-2Cl = 3:1, 1:1, 1:3, and 1:9). Without the need to isolate individual components, these MBAs can be utilized directly as electron acceptor to fabricate QOSCs. Compared with binary and ternary devices, QOSCs based on PM6: MBAs exhibit dramatically improved PCEs. Further device optimization, by using 2PACz as hole transport layer and DIB as an additive, PM6:MBA13-based device achieves a state-of-the-art PCE of 20.10%, among the highest values reported for QOSCs to date. Obviously, this method simplifies the material synthesis and device fabrication process for QOSCs. This study provides a feasible method to synthesize MBAs and subsequently fabricate high-performance QOSCs, and thereby opens up a new venue for the further optimization of OSCs.