Surface-Modified Group I–III–VI Semiconductor Colloidal Quantum Dots with Customized Photoluminescence and Enhanced Electronic Properties

Group I–III–VI semiconductor colloidal quantum dots (QDs) emerge as an exciting family of nanocrystals increasingly attractive for the next-generation solution-processed optoelectronic devices thanks to their low-cost synthesis and environmentally friendly, Cd- and Pb-free compositions. Here, a universal approach based on room-temperature surface treatment and cation exchange has been demonstrated to modify the surface and composition of CuInS2, CuInSe2 and AgInS2 QDs. The absorption cross-section was enhanced and the emerging photoluminescence properties were finely tuned in the near-infrared region owing to great control over the size and composition of the modified QDs. While the field-effect transistors (FETs) based on the original untreated QDs exhibit p-type behavior and suffer from low hole mobility (μh), surface passivation of these QDs with an inorganic layer of S2– leads to a clear switch to n-type behavior accompanied by a great enhancement in electron mobility (μe). Moreover, additional diffusion of Zn atoms into the structure heals the acceptor sites and nullifies the effect of metal vacancies and antisite defects. The FET devices based on the final modified CuInS2 and AgInS2 QDs demonstrate exceptionally high μe of 5.53 and 7.50 cm2 V–1 s–1, respectively, 4 orders of magnitude higher than μh of the starting untreated QDs.