n+-p-p+structure InP solar cells grown by organometallic vapor-phase epitaxy

The fabrication of n⁺-p-p⁺InP solar cells by OMVPE has been studied. A conversion efficiency (active area) as high as 20 percent under AM1.5 illumination has been obtained. It is experimentally verified that the n⁺-p-p⁺InP solar cell has a higher resistance to radiation degradation than the n⁺-p InP solar cell. Diode characteristics and photovoltaic performances such as saturation current density, diode-ideality factor, and open-circuit voltage for the n⁺-p-p⁺cells are found to drastically deteriorate when junction depth decreases to ≤ 0.15 µm. An electron concentration dependence of a hole diffusion length in n-InP is estimated from the measurement of photoluminescence spectra. For the improvement of photovoltaic performances, a series of systematic examinations has been made on the relationship between collection efficiency and hole diffusion length from photogenerated carrier distribution analysis.