Solvent annealing for morphology control to realize high efficiency all-small-molecule organic solar cells

Abstract

Morphology control of all-small-molecule (ASM) organic solar cells (OSCs) is crucial for improving their efficiencies. However, choosing an appropriate strategy for these systems is highly challenging. In this study, carbon disulfide (CS₂) is demonstrated to tune morphology and synchronously enhance the power conversion efficiencies (PCEs) of BTR-Cl/Y6 based ASM-OSCs. The improved PCEs are mainly due to the with better phase separation resulting in reduced recombination, prolonged carrier lifetime, and facilitated charge extraction. Thus, compared with TA (thermal annealing) based devices, the CS₂-treatment based devices exhibit better performance with FF enhanced from 65.8% to 74.2% and J_SC increased from 24.23 to 24.78 mA cm⁻², leading to a higher PCE of 15.5%. These findings demonstrate that the solvent (CS₂) treatment can be a simple and effective way to deliver highly efficient OSCs.