Enhanced performance of small GaAs solar cells via edge and surface passivation with trioctylphosphine sulfide

We have extended our previous work on trioctylphosphine sulfide (TOP:S) to further elucidate the mechanisms of this chemical passivation for small GaAs solar cells. Photoluminescence (PL) measurements indicate monolayers of TOP:S on GaAs significantly increases the electronic quality of both n- and p-doped wafers. TOP:S was also applied to an “ultra small” GaAs solar cell (0.31 mm²) to test its ability to passivate devices with the relevant dimensions for microconcentrator schemes. After the cells were briefly soaked in TOP:S, the efficiency of the cell was boosted by 1% (absolute), even after a rinse in toluene to remove all but a few monolayers of TOP:S, confirming sidewall passivation.