The Polymer Society of Korea

Abstract

Infrared avalanche photodiodes (APDs) based on colloidal quantum dots (CQDs) are promising for scalable, solution-processed imaging and sensing. However, conventional layer-by-layer (LBL) solid-phase ligand exchange can introduce interfacial nonuniformity and trap-assisted leakage, limiting reliable avalanche operation. Here, we develop benzoic acid (BA)–based CQD inks enabled by solution-phase ligand exchange, which stabilizes CQDs in the ink and enables simple deposition of thick active layers for avalanche multiplication. Compared with LBL-processed QD APDs, BA-ink devices show improved responsivity and more effective avalanche amplification. We further apply electric field engineering to reduce the breakdown voltage (V_br) enabling lower bias avalanche operation. This work establishes a practical CQD ink platform for low-voltage infrared QD APDs.