Study of Nitride-Based Compound Photovoltaic Cells

Abstract

In this dissertation GaN/InGaN double-heterostructure photovoltaic (PV) cells have been characterized and the theoretical photovoltaic properties were also calculated used for comparison From theoretical simulation higher efficiency can be obtained in GaN/InGaN double-heterostructure photovoltaic cells with higher In composition in i-InGaN intrinsic layer The corresponding conversion efficiency of fabricated GaN/InGaN photovoltaic cells with In compositions of 10% 12% and 14% is 0 51% 0 53% and 0 32% respectively GaN/InGaN photovoltaic cells with In composition of 10% showed high open-circuit voltage of 2 07 V and ?ll factor of 80 67% and the decrease of open-circuit voltage and ?ll factor was observed as In composition increasing from 10% to 14% The difference of GaN/InGaN photovoltaic properties between theoretical simulation and experimental measurement could be attributed to the inferior quality of InGaN epilayer and GaN/InGaN interface generated as the increase of In composition When the characteristics of InGaN photovoltaic cells were compared between illumination conditions of one sun and 120 suns the photovoltaic properties – open-circuit voltage (VOC) short-circuit current (ISC) and ?lling factor (FF) – measured in fabricated GaN/InGaN photovoltaic cells improved more than those calculated from the simulation This result could be tentatively attributed to the trap-?lling effect under a high injection density of photo-generated carriers which would relatively reduce the series resistance and increase the shunt resistance The improvements in the conversion ef?ciencies of the GaN/InGaN photovoltaic cells between illumination conditions of one sun and 120 suns were 4 6% and 70 8% for simulated and measured conversion ef?ciencies respectively The differences between the simulated results and measurements of actual GaN/InGaN photovoltaic cells are consistent Finally the improvement of conversion ef?ciency of InGaN photovoltaic cells with inverted textured surface (ITS) was verified in this study InGaN photovoltaic cells with ITS showed short-circuit current density and conversion ef?ciency of 0 63 mA/cm2 and 1 01% which are 68 17% and 73 33% higher than the characteristics of conventional InGaN photovoltaic cells respectively The improvement can be attributed to the reduction of both the shading effect of the electrode contact pad and surface re?ection of the incident irradiation

Date of Award	2018 Jul 31
Original language	English
Supervisor	Shoou-Jinn Chang (Supervisor)