Figure 1. Resistance dependent PhotoVoltage (RPV) measurement circuit (top) and timing diagram (bottom).

A low light intensity nanosecond laser pulse is used to photogenerate charge carriers inside (for example) the semiconductor junction of an organic solar cell. Low light intensity is critical in the RPV experiment to ensure operation within the “small charge extraction mode” where the internal electric field distribution in the film is not altered by transported charges. After photogeneration, the charge carrier transport through the film is driven by the built-in or the applied external electric field, and the resulting transient photosignal is recorded by an oscilloscope. The transient photosignals are measured at various load resistances R_load.