Morphologically engineered multi-component organic solar cells with stratified donor distribution and alloyed acceptors for enhanced efficiency and stability

The strategy of integrating multiple components within the bulk-heterojunction layer of organic photovoltaics (OPVs) has proven effective in enhancing device performance and demonstrates broad potential applications. Nonetheless, achieving precise control over the morphology in such a multifaceted system presents a significant challenge. In this work, we introduce an innovative sequential casting technique to fabricate highly efficient quaternary OPVs with a meticulously tailored morphology featuring layers of stratified donor distribution and composite alloyed acceptors. The layered configuration of D18/PTQ10, with distinct crystalline domains, establishes a dedicated hole-transport pathway, while the alloyed BTP-eC9:Y6-O acceptors are evenly dispersed across the layered D18/PTQ10 donor phase. This carefully crafted morphology presents a gradient and interpenetrated donor/acceptor phase separation at an ideal length scale, which facilitates exciton dissociation, minimizes energetic disorder, and mitigates recombination. As a result, a power conversion efficiency close to 19% with excellent operational stability (extrapolated T₈₀ = 818 h) was achieved. This work offers valuable insights into the morphological engineering of multicomponent OPVs for improved performance. © 2024 Elsevier Ltd