Enhanced performance of a solar cell based on a layer-by-layer self-assembled luminescence down-shifting layer of core-shell quantum dots**Project supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2017PF011), the National Natural Science Foundation of China (Grant No. E020701), and the Doctoral Scientific Research Foundation of Binzhou University, China (Grant No. 2014Y10).

Abstract

In this paper, core–shell quantum dots (QDs) with two polar surface functional groups (ZnSe/ZnS–COOH QDs and ZnSe/ZnS–NH2 QDs) are synthesized in an aqueous phase. Photoluminescence (PL) and absorption spectra clearly indicate luminescence down-shifting (LDS) properties. On the basis of QDs, surface functional group multilayer LDS films (M-LDSs) are fabricated through an electrostatic layer-by-layer (LBL) self-assembly method. The PL intensity increases linearly with the number of bilayers, showing a regular and uniform film growth. When the M-LDS is placed on the surface of a Si-based solar cell as an optical conversion layer for the first time, the external quantum efficiency (EQE) and short-circuit current density (Jsc) notably increases for the LDS process. The EQE response improves in a wavelength region extending from the UV region to the blue region, and its maximum increase reaches more than 15% between 350 nm and 460 nm.