Title: Design ad Fabrication of Nitride-based Solar Cells and Intergration for Tandem Cell
Dr. Ougazzaden, Advisor
Dr. Salvestrini, Chair
The objective of the proposed research is to fabricate indium gallium nitride/gallium nitride (InGaN/GaN) photovoltaics devices grown on 2D hexagonal boron nitride (h-BN) by metal-organic vapor phase epitaxy (MOVPE) and their integration into InGaN/Si tandem solar cells. Recent advances in epitaxial growth have led to the Van der Waals epitaxy of III-nitride devices on 2D layered h-BN. This advance has the potential for wafer-scale transfer to arbitrary substrates, which would allow III-N devices to be used more flexibly in a broader range of applications. The choice of the InN – GaN material system for photovoltaics stems from its energy band gap stretching from 0.78-3.42 eV, which covers the entire visible spectrum. We have developed novel solutions to the problems of phase separation, v-pits, and low quality p-GaN and absorber regions which have resulted in the highest reported peak external quantum efficiency for III-nitride based solar cells. The development of a fabrication process for the InGaN-based solar cells has been also investigated and will be adapted for devices grown on 2D h-BN. The weak van der Waals bonds between h-BN atomic layers break easily, allowing the devices to be mechanically lifted off from the sapphire substrate and directly integrated into an InGaN/Si tandem solar cell. To limit the cracks formation during this step, an elastomeric stamp assisted transfer method will be applied.