Suppressing Exciton–Vibration Coupling via Intramolecular Noncovalent Interactions for Low-Energy-Loss Organic Solar Cells

Abstract

Minimizing energy loss is crucial for breaking through the efficiency bottleneck of organic solar cells (OSCs). The main mechanism of energy loss can be attributed to non-radiative recombination energy loss (ΔE_nr) that occurs due to exciton–vibration coupling. To tackle this challenge, tuning intramolecular noncovalent interactions is strategically utilized to tailor novel fused ring electron acceptors (FREAs). Upon comprehensive analysis of both theoretical and experimental results, this approach can effectively enhance molecular rigidity, suppress structural relaxation, reduce exciton reorganization energy, and weakens exciton–vibration coupling strength. Consequently, the binary OSC device based on Y-SeSe, which features dual strong intramolecular Se ⋅ ⋅ ⋅ O noncovalent interactions, achieves an outstanding power conversion efficiency (PCE) of 19.49 %, accompanied by an extremely small ΔE_nr of 0.184 eV, much lower than those of Y-SS and Y-SSe based devices with weaker intramolecular noncovalent interactions. These achievements not only set an efficiency record for selenium-containing OSCs, but also mark the lowest reported ΔE_nr value among high-performance binary devices. Furthermore, the ternary blend device showcases a remarkable PCE of 20.51 %, one of the highest PCEs for single-junction OSCs. This work demonstrates the effectiveness of intramolecular noncovalent interactions in suppressing exciton–vibration coupling, thereby achieving low-energy-loss and high-efficiency OSCs.