Analysis of transient photocurrents in Cu(In,Ga)Se2 thin film solar cells

A transient photocurrent measurement with a zero-field time-of-flight configuration was carried out on ITO/ZnO/CdS(n-type)/Cu(In,Ga)Se2(p-type, Eg=1.15 eV)/Mo/glass solar cell to get the information about the minority carrier transport on the Cu(In,Ga)Se2 film. The transient photocurrent was recorded after the incidence of a subnanosecond pulse light (500 nm wavelength) from the back side through the Mo thin film (<0.5 μm). The analysis of the transient photocurrent was conducted by using the time-dependent diffusion current equation. Consequently, the values of 1.0 cm2/s, 100 ns, and 103 cm/s as the diffusion coefficient, the minority carrier lifetime, and the recombination velocity in the Cu(In,Ga)Se2/Mo interface, respectively, were obtained on the Cu(In,Ga)Se2 film. These data corresponded to the electron beam induced current line profile data, and the experimental data of J0, analyzed by current–voltage characteristics.