SEM measurement of diffusion lengths, recombination velocity, and junction collection efficiency in heterojunction solar cells: Application to CuxS/CdS

Existing theory for scanning electron microscope (SEM) measurement of diffusion length and surface recombination velocity in P-N junctions has been extended to apply when space charge region (SCR) recombination and energy losses occur. Such phenomena are important in heterojunction devices. When applied to SEM data taken on CuxS/CdS solar cells as a function of air heat treatment time at 120°C, this analysis showed dramatic changes occurring in the junction collection efficiency but no significant changes in diffusion lengths or surface recombination velocity. This indicates that SCR phenomena play a major role in the evolution of these devices' performance with heating.