Capacitance effects in high-efficiency cells

Frequently transient measurement techniques lead to capacitance effects which complicate the accurate measurement of the performance of high efficiency solar cells. The photo-current-response measurement (PCR), developed at ESTI, offers a tool for the investigation of these capacitance effects. This paper describes the theory of capacitance effects and the diffusion capacitance as experimental results achieved by the PCR-method. The theory shows that the diffusion capacitance is strongly dependent on the minority carrier diffusion length and lifetime. In the future the PCR-method could be used for the determination of this solar cell parameter. We show, using monochromatic light pulses, that the induced diffusion capacitance charge (Q(diff)) is exponentially dependent on the bias voltage and linearly dependent on the light intensity. Finally, the capacitance effect is made clearly visible by the generation of the current-voltage characteristic from PCR-measurements.