High-efficiency AlGaAs/GaAs photovoltaic converters with edge input of laser light

High-efficiency photovoltaic converters (PVCs) have been developed and fabricated by liquidphase epitaxy in the AlGaAs–GaAs system with laser light ($\lambda$ = 850 nm) introduced through the edge surface in parallel to the plane of the $p$–$n$ junction of the device structure. To raise the efficiency of light “capture” by the $p$–$n$ junction, an Al$_{x}$Ga$_{1-x}$As waveguide layer is formed, in which the content of aluminum gradually varies from $x$ = 0.55 to 0.15 so that the refractive index gradient is created in this layer and light beams are diverted toward the $p$–$n$ junction. When a PVC (having no antireflection coating) is exposed to 0.1- to 0.2-W laser light, an efficiency of 41.5% is obtained. Depositing an antireflection coating on the edge surface of a PVC raises its efficiency to 55%.