LAUSR

Mitigating series resistance is crucial to the efficiency of concentrator solar cells at high current density. Conventional AlGaInP junction designs for the top junction of III–V multijunction cells present a challenging tradeoff between series resistance on the one hand and current collection and voltage on the other hand. In this article we discuss the physics of a reverse heterojunction solar cell that aims to improve on this tradeoff by combining a high bandgap Al0.18Ga0.33In0.49P base and a lower bandgap (Al)GaInP emitter. The high mobility of the emitter leads to a relatively low series resistance, compared with a high bandgap homojunction cell. The electroluminescence spectrum shows emission peaks from both the emitter and base, leading to an open-circuit voltage that is not strictly dominated by either layer. The reverse heterojunction design is increasingly beneficial as the one-sun voltage increases.