Enhancement of the conversion efficiency of GaN-based photovoltaic devices with AlGaN/InGaN absorption layers

InGaN/sapphire-based p-i-n type photovoltaic (PV) devices were shown to have Al0.14Ga0.86N/In0.21Ga0.79N heterostructures that enhance the extraction of photogenerated carriers from active layers. With an appropriately increased barrier height in AlGaN/InGaN absorption layers, PV devices exhibit lower RS despite the increase in conduction-band discontinuity compared with GaN/InGaN superlattice absorption layers. This improvement can be attributed to polarization-induced electric fields enhanced by the incorporated aluminum in barrier layers. The enhancement is beneficial to increase built-in electric fields. Subsequently, the photogenerated carriers can escape more easily from recombination or scattering centers. Under 1 sun air-mass 1.5 standard testing conditions, the Al0.14Ga0.86N/In0.21Ga0.79N PV device exhibits high VOC (2.10 V) as well as an enhanced fill factor (0.66) and JSC (0.84 mA/cm2) corresponding to a power conversion efficiency of 1.16%.