Photoluminescence-based measurement technique of surface recombination velocity for high efficiency silicon and compound semiconductor solar cells

This paper shows that the authors´ recently proposed photoluminescence surface state spectroscopy (PLS³) technique allows an in-situ, contactless and nondestructive determination of the value of the solar cell effective surface recombination velocity (S) under sunlight illumination and the surface/interface state density (N _SS) distributions. This technique is successfully applied to measurement of the values of S at variously passivated Si surfaces. A best value of 3,000 cm/s is obtained under 1 sun condition for thermal oxidation. S is greatly reduced under concentrated sunlight. N_SS distributions at compound semiconductor surfaces and heterointerfaces are also characterized to optimize the fabrication process of compound semiconductor solar cells. Formation of Si interface control layer (ICL) between InGaAs and SiO₂ greatly reduces the interface states. Growth interruption at AlGaAs/GaAs heterointerface produces high density of interface states. InAlAs/InGaAs heterointerfaces are also investigated. These results indicate that the new PLS³ technique is useful for the characterization and optimization of the fabrication processes of the silicon and compound semiconductor solar cells