A quantitative study on loss processes in multiple energy gap solar cells

Heat generation due to loss processes in solar cells leads to a temperature rise, which causes an inevitable impact on the performance of photovoltaic devices. Heat conduction, convection and radiation are synchronously involved in the heat exchange between the cell and environment. Meanwhile, the thermalization loss process inside the cell makes the energy conversion of the cell complicated. So far a number of investigation efforts have mainly been concentrated on single junction solar cells and little work has been devoted to studying the loss processes in multiple energy gap solar cells. This paper studies the loss processes of multiple energy gap solar cells, including both the intrinsic and extrinsic losses. In single junction solar cells, the most important losses are below E_g and thermalization losses, covering more than half of the incident energy. While in this work, the thermalization loss in a CH₃NH₃PbI₃ perovskite-crystalline silicon double junction solar cell drops 39.9% compared with that in a Si solar cell. In a CH₃NH₃PbI₃ perovskite-crystalline silicon-germanium treble junction solar cell, the below E_g loss drops 79.5% compared with that in a crystalline silicon solar cell and the cell efficiency increases about 10 percent. The multiple energy gap solar cells effectively limit the dominant losses and enhance the cell efficiency.