Suppression of lowering in conversion efficiency under temperature variation for multijunction laser power converters

Abstract

Conventional multijunction photovoltaic cells used for optical wireless power transmission, often referred to as laser power converters, currently involve a serious problem. The conversion efficiency lowers under temperature variation more notably than that of single-junction cells, because of changing absorption coefficient and resultant current mismatching among the subcells. Light-trapping using an anti-reflection coating on the front face and a diffuse reflector on the rear face solves this problem, because intensity distribution of the incident light inside the cell remains almost uniform even though the absorption coefficient changes. An angular-selective filter on the front face further improves the efficiency.