Surface tailoring enables colloidal quantum dot: Metal-oxide nanocrystal hybrid ink for broadband photon energy conversion

Blending multiple functional nanoparticles (NPs) into one solvent and forming a stable hetero-ink is a promising technology to realize efficient solution-processed heterogeneous structures for next-generation energy conver-sion. However, differences in the surface nature of NPs hinder the formation of stable hybrid ink, causing un-favorable morphologies in film formation. In this work, we demonstrate a stable hybrid ink using colloidal quantum dots (CQDs) and metal-oxide NPs. The modified synthesis route of ZnO NPs enables modulation of their surfaces, resulting in ink that is fully miscible in alkyl amine solvents with CQDs. This hybrid ink allows the formation of conformal heterogeneous thin-films via a single step spin-casting. Based on this result, we devise an efficient planar-mixed heterojunction solar cell, which exhibits a 12.8% power conversion efficiency (PCE), one of the highest performances among prior CQD:metal-oxide hetero-structured hybrid solar cells.