Power maximization in III-V sub-millimeter, radial front contacted cells for thin micro-concentrators

Sub millimeter scale solar cells coupled with medium concentration lenses can reduce the balance of system costs of concentrating photovoltaics by creating thin and highly efficient concentrators with relaxed tracking requirements. This paper shows the design, fabrication, simulation, and testing of micro-sized photovoltaics that have unique perimeter front contacts outside the optical collection area. The design of the device considered the need for low resistance current carrying layers while minimizing optical losses. The paper also shows the successful fabrication of InGaAs cells as well as of GaAs cells transferred onto silicon substrates. The simulations and experimental measurements show that small cells of this type 1) suffered from slightly lower voltage levels caused by proportionally larger dark currents 2) peaked their efficiencies at higher concentration levels compared to larger ones 3) performed better overall.