Efficient All-Small-Molecule Organic Solar Cells Based on an Asymmetric Coumarin-Anthracene Donor

Ternary organic solar cells (OSCs) based on all-small molecules represent a promising avenue toward high-performance and stable devices. In this study, we introduce an efficient all-small-molecule ternary OSC, incorporating 20 wt % of the medium bandgap electron acceptor DBTBT-IC into the CA-CO:Y6 binary blend, resulting in a notable power conversion efficiency (PCE) of 15.42%. This marks an improvement of ∼25% compared to the CA-CO:Y6 binary device’s (PCE 12.27%). Moreover, the large molecular electrostatic potential (ESP) difference between the CA-CO donor and Y6 acceptor reveals efficient charge transfer, creating an induced intermolecular electric field to facilitate charge generation within the materials. The ternary device also exhibits lower nonradiative energy loss than binary devices. This work highlights the significance of simple coumarin-based donors in enhancing the performance of OSCs by promoting charge carrier transport while minimizing recombination.