Size-dependent polymer/CuInS2 solar cells with tunable synthesis of CuInS2 quantum dots

This paper reports the size-dependent performance in polymer/CuInS2 solar cells with tunable synthesis of chalcopyrite CuInS2 quantum dots (QDs) by the solvothermal method. The CuInS2 QDs of 3.2–5.4 nm in size are fine tuned by the reaction time in the solvothermal process with the slow supply of In3+ ions during the crystallization, and the band gaps increased with QDs sizes decreasing according to the results from the characterization of sizes, morphologies, component elements, valence states and band gaps of CuInS2 QDs. We fabricated MEH-PPV/CuInS2 solar cells, and the photoactive layer of device displayed size-dependent light-harvesting, charge separation and transport ability. Moreover, the solar cells exhibit size-dependent short circuit current (Jsc) and open circuit voltage (Voc), with higher performance in both Jsc and Voc for smaller CuInS2 QDs, resulting in the maximum power conversion efficiency of ca. 0.12% under the monochromic illumination at 470 nm; CuInS2 QDs actually serve as an effective electron acceptor material for the MEH-PPV/CuInS2 solar cells with the wide spectral response extending from 300 to 900 nm.