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)-10(17) cm(-3) in the bulk semiconductor is required to produce high efficient PV cells by the Zn diffusion process [1-3]. 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 mm(2) (211) and 10x10 mm(2) (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/cm(2) range and 63 % at 5 A/cm(2). The open circuit voltage Voc increases from 0.44 V (1 A/cm(2)) up to 0.49 V (5 A/cm(2)) for the small area cell.