Spectral response measurements of two-terminal triple-junction a-Si solar cells

Abstract

A method of measuring the spectral response of each component junction in a two-terminal triple-junction a-Si solar cell has been developed. The method uses a white bias light and off-the-shelf optical interference filters selected to reduce the bias light encountering each component junction. The a-Si top junction is measured when the cell is biased with wavelengths of 585–1100 nm, the a-Si middle junction is measured when the cell is biased with wavelengths of 350–505 nm and 795–1100 nm and the a-SiGe bottom junction is measured when the cell is biased with wavelengths of 380–670 nm. In turn, the chopped light from a monochromator is used to measure the spectral response of the low-biased junctions. Spectral response curves of the Solarex a-Si/a-Si/a-SiGe triple junction solar cell are presented. In addition, the AMO Isc (short circuit current) of this individual cell type is confirmed to be within ±2% of the Isc obtained when the spectral response of the current limiting junction is integrated with either the AM0 spectral irradiance or that of a closely matched (±10% from 350 nm to 900 nm) X-25 Mark II solar simulator.