1064 nm InGaAsP multi-junction laser power converters

Laser photovoltaic devices converting 1064 nm light energy into electric energy present a promising prospect in wireless energy transmission due to the commercial availability of high power 1064 nm lasers with very small divergence. Besides their high conversion efficiency, a high output voltage is also expected in a laser energy transmission system. Meanwhile, 1064 nm InGaAsP multi-junction laser power converters have been developed using p+-InGaAs/n+-InGaAs tunnel junctions to connect sub-cells in series to obtain a high output voltage. The triple-junction laser power converter structures are grown on p-type InP substrates by metal-organic chemical vapor deposition (MOCVD), and InGaAsP laser power converters are fabricated by conventional photovoltaic device processing. The room-temperature I–V measurements show that the 1 × 1 cm2 triple-junction InGaAsP laser power converters demonstrate a conversion efficiency of 32.6% at a power density of 1.1 W/cm2, with an open-circuit voltage of 2.16 V and a fill factor of 0.74. In this paper, the characteristics of the laser power converters are analyzed and ways to improve the conversion efficiency are discussed.