Highly efficient ITO-free organic solar cells with a column-patterned microcavity

Abstract

Achieving high-efficiency organic solar cells (OSCs) requires well balancing the trade-off between the voltage loss and photocurrent generation of bulk heterojunction (BHJ) blends. In this work, we develop high-performance ITO-free OSCs through incorporating a newly designed column-patterned microcavity (CPM) for effective optical confinement of thin near-infrared BHJs. With the assistance of optical interference, light scattering and local surface plasmons of patterned electrodes, the photocurrent density (J_sc) values of OSCs are largely improved for thin BHJs with near 100 nm thickness. In addition, the high open circuit voltage (V_oc) and fill factor (FF) are secured in self-assembled monolayer (SAM) treated ITO-free OSCs. As a result, the power conversion efficiencies (PCEs) of ITO-free OSCs in the inverted architecture have reached 15.5% and 17.5% for ternary PBDB-T-SF:ITIC-Th:IT-4F and binary PM6:Y6 blends, respectively, yet exhibiting the desirable features of less incident angle dependence. Overall, these OSCs with CPM not only reach significant performance-enhancement over the corresponding ITO devices, but also represent the best performing ITO-free OSCs so far.