Enhancing the performance of Ga(In)NAs intermediate-band solar cells

Intermediate band solar cells (IBSCs) have the potential to overcome the efficiency limit of single-bandgap solar cells. Dilute nitride III–V alloys, with splitting of the conduction band due to band anticrossing, can be used as the intermediate-band material for solar cell applications. In this work, we report on the introduction of engineered GaInNAs alloy, with low (dilute) In and N contents, as IBSC material and the comparison of the performances of GaInNAs-based and the corresponding In-free GaNAs-based IBSCs grown on GaAs (100) substrate. Introduction of a small amount of In (3%) in a GaN _0.011 As _0.989 -based IBSC was found to noticeably increase the short-circuit current, I _sc , at the expense of a small decrease in the open-circuit voltage, V _oc . When annealed at 750 °C for 90 s, significant enhancements in I _sc and V _oc are seen, especially in the In-containing solar cell. The observed In-related enhancement in cell parameters after annealing is related to In-promoted bandgap tailoring and efficient curing of carrier traps during annealing. This occurred without change in the macroscopic composition of the GaInNAs alloy, most likely by In-N bond formation upon annealing, a phenomenon which does not exist in the GaNAs alloy.