Space-charge-limited current and capacitance in CuXS/CdS solar cells

The unusual behavior of CuxS/CdS solar cells is better described with space-charge-limited current (SCL I) than with standard junction models. The SCL I theory provides the first quantitative explanation of these devices´ I-V characteristics including their non-exponential form, the dark-light crossover, the temperature independent slope in addition to qualitatively modeling the voltage variation of capacitance. This is accomplished with trapping parameter values well known to be characteristic of Cu compensated CdS. It indicates that the voltage dependence of current is controlled by mechanisms entirely different than previously proposed with important implications for device fabrication and optimization and ultimate device performance.