Thermophotovoltaic GaSb Cells Fabrication and Characterisation

For production of highly effective photoconverters semiconductor materials with strictly determined parameters are required. For thermophotovoltaic (TPV) GaSb cells homogeneous Te-doping level of (2-7)*1017 cm-3 in the bulk semiconductor is required to produce high efficient PV cells by the Zn diffusion process. In this paper we present data on investigation of the performance of the cells obtained on different GaSb:Te wafers of (100) and (211) orientation. Based on classical I/V measurements and external quantum efficiency (EQE) curves, we analyze cell performances in order to improve all fabrication stages like wafer surface preparation, p-type GaSb emitter elaboration by the zinc diffusion process, antireflection coating deposition and contact realization. Today good performances are obtained on both 3.5 X 3.5 mm2 (211) and 10X10 mm2 (100) GaSb cells. We obtained EQE of 70-76 % in the 800-1600 nm range for the first one and 80-88 % in the same spectrum for the second one. Electrical characterization gives respectively, the fill factor (FF) from 67.8 % down to 65.8 % in the 1-2 A/cm2 range and 63 % at 5 A/cm2. The open circuit voltage Voc increases from 0.44 V (1 A/cm2) up to 0.49 V (5 A/cm2) for the small area cell.