Deep junction III–V solar cells with enhanced performance

Abstract

The influence of junction depth in III–V solar cell structures was investigated for GaAs and InGaP cells. Typical III–V solar cells employ a shallow junction design. We have shown that for both investigated cell types, a deep junction close to the back of the cell structure performs better than shallow junction cells. At the maximum power point the deep junction cells operate mainly in the radiative recombination regime, while in the shallow junction cells non‐radiative recombination is dominant. The steeper slope of the IV curve boosts the fill‐factor by 3–4%, which is thereby the most improved cell parameter. In order to minimize collection losses in the upper part of the solar cell, the optimal thickness of the GaAs deep junction cell is only two‐thirds of a shallow junction cell. The associated lower cell current is more than compensated by the higher fill‐factor and open circuit voltage. The best deep junction GaAs cell shows a record efficiency of 26.5% for a GaAs cell on substrate. In the thinner InGaP deep junction cell the absence of current loss, leads to 1.6% higher efficiency than for the shallow junction cell.