AlInAs heterojunction emitter for highly efficient inverted GaInAs solar cells grown by molecular beam epitaxy

In III-V solar cells, much research has been conducted to improve the conversion efficiency by applying a rear heterojunction (RHJ) structure as a mean of controlling the built-in potential. In this work, a p-type Al0.48In0.52As rear heterojunction (RHJ) emitter was employed in Ga0.47In0.53As solar cells with 0.75 eV in bandgap grown by molecular beam epitaxy. A typical RHJ solar cell structure showed increase in reverse saturation current density (J0) since the positions of the pn interface and the heterointerface are the same. On the other hand, the introduction of an appropriate thicknesses of n-AlInAs spacer layer between p-AlInAs emitter and n-GaInAs base can separate each interface position and was found to reduce J0 leading to improved VOC and FF. In addition, the backside reflective structure was employed to optimized RHJ solar cells, showing the highest conversion efficiency of 15.38% among the reported values in the literature so far due to promoted light trapping.