Dual-junction gallium nitride solar cells with hybrid tunnel junction layers

The authors reported the fabrication of a dual-junction (2J) GaN solar cell (SC) with hybrid tunnel junction (TJ) layers. Compared with the single-junction (1J) SCs, it was found from the XRD spectra that the crystal quality of the SC with TJ was almost identical. However, the effciencies of bottom 1J SC, top 1J SC, and 2J SC increase from 1.18 to 1.07, 1.12 to 1.20, and 1.59 to 1.73, respectively, when the concentrated suns increased from 1 to 100 suns. It was found that the use of hybrid TJ layers could result in a higher conversion effciency in 2J SC and was essential in SCs for serially connecting multiple active junctions.