COMPARISON OF MEASURED PERFORMANCE AND THEORETICAL LIMITS OF GaAs LASER POWER CONVERTERS UNDER MONOCHROMATIC LIGHT

Evaluation of GaAs laser power converters (LPC) is reported in light of theoretical maximum limits calculated with detailed balance method as proposed by Shockley and Queisser (SQ). Calculations were done for three different theoretical structures of LPCs homogeneously illuminated by monochromatic light. Effects of LPC thickness, central wavelength of a monochromatic light source and various irradiance levels are discussed. Reflection of incident light from the interface between air and GaAs is calculated and countermeasures in the form of single and double layer anti reflection coatings are theoretically studied. Measurements of single junction, single segment GaAs LPC illuminated by monochromatic light with central wavelength lambda(0) = 808 nm are presented and compared with the theoretical maximum values. The conversion efficiency eta(meas) = 54,4 % was measured for GaAs LPC illuminated with power density of monochromatic light p(illum) = 14,3 W/ cm(2) at the temperature of the LPC casing T = 302 K. For the same parameters conversion efficiency eta(SQ) = 76,6 % was calculated resulting in utilization ratio eta(meas)/eta(SQ)= 0,71. Measured J(sc) and V-oc achieve 88,5 % and 89,2 % of theoretically calculated SQ limit values.