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

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.

Automated summary

This study has achieved high-performance ITO-free organic solar cells through the incorporation of a newly designed column-patterned microcavity (CPM) for effective optical confinement of thin near-infrared BHJs. By utilizing optical interference, light scattering and local surface plasmons of patterned electrodes, the photocurrent density of OSCs was significantly improved for thin BHJs with near 100 nm thickness.