Multi-junction Solar Cell System Research Articles

Improving GaP Solar Cell Performance by Passivating the Surface Using AlxGa1-xP Epi-Layer

A good candidate for the top junction cell in a multi-junction solar cell system is the GaP solar cell because of its proper wide band gap. Here, for the first time, we passivate the front surface of these GaP solar cells with an AlGaP layer. To study the passivation effect of this layer, we design a novel growth procedure via liquid phase epitaxy. X-Ray diffraction results show that the resulting passivation epitaxial layer is of good quality. Integrated quantum efficiency measurements show an 18% increase in current due to the AlGaP. The current-voltage measurements indicate that with this AlGaP surface passivation layer, the GaP solar cell's efficiency is 2.90%. This is an improvement over previously reported results for GaP solar cells.

Wide Band Gap Gallium Phosphide Solar Cells

Gallium phosphide (GaP), with its wide band gap of 2.26 eV, is a good candidate for the top junction solar cell in a multijunction solar cell system. Here, we design, fabricate, characterize, and analyze GaP solar cells. Liquid phase epitaxy is used to grow the semiconductor layers. Four generations of GaP solar cells are developed and fabricated with each solar cell structure being designed and improved based on the first principles analyses of the predecessor solar cells. Quantum efficiency and current-voltage measurements are used to analyze the solar cell performance and to develop predictive models. We create a GaP solar cell with an efficiency of 2.42% under AM 1.5G one sun illumination.