Morphological enhancement and charge recombination mitigation in non-fullerene organic solar cells through solvent vapor annealing

Abstract This study explores the efficacy of solvent vapor annealing (SVA) in enhancing the performance of organic solar cells (OSCs) by mitigating charge recombination and improving charge extraction, which are prevalent issues limiting their efficiency. Focusing on an OSC blend with known suboptimal characteristics, we specifically examine the effects of SVA on the blend’s morphology, optical properties, and charge dynamics. Notably, SVA treatment significantly increases the short-circuit current density ( J sc ) from 17.24 ± 1.66 mA cm −2 to 26.92 ± 1.06 mA cm −2 for an optimal 30 s treatment. However, extended treatment durations inversely affect the J sc , indicating the need for precise control of the SVA protocol. The treatment also induces shifts in the optical absorption spectra and morphological changes. The impact of improved optical properties on charge photogeneration was analyzed by transfer matrix method simulations, while transient absorption, transient photovoltage (TPV) and transient photocurrent measurements helped to understand the dynamics of charge recombination. Both features explain the increase in experimental cell performance. These findings bring light to the mechanisms behind the use of SVA to enhance OSC performance and underscore its potential by careful implementation of a simple post-processing technique.