Impact of luminescent down-shifting EVA layers onto CIGS solar cells

摘要

Copper indium gallium diselenide (CIGS) solar cells exhibit poor short-wavelength response, primarily due to parasitic absorption by their window and cadmium sulphide (CdS) buffer layers. Luminescent down-shifting (LDS) can be used to improve this performance without any modification to the devices' structure and manufacturing methodology. The selection of the optimal luminescent material(s) is based on the external quantum efficiency profile of a device at short wavelengths, which is strongly dependent on the CdS buffer layer thickness. In this work, two sets of CIGS solar cells with different CdS layer thicknesses are tested under LDS layers made from ethylene vinyl acetate (EVA). For devices with 50 nm-thick CdS layers, an overall enhancement of 0.12 mA/cm~2 is achieved using a single-dye doped LDS layer. For devices with 100 nm thick CdS layers, an overall enhancement of 0.12 mA/cm~2 is again achieved, but this time using an LDS layer doped with a mixture of two dyes. Further performance enhancement can be achieved if the solar cells are designed to better match the modified spectrum and the devices are optimised as a system instead of separate components. The use of LDS layers offers the additional benefit of colouration, which can encourage further utilisation of PV devices in architectural applications.