Optical Pulses to Characterize Large Solar Cell Wafers

In this study, we developed the novel characterization of semiconductor materials by applying single optical pulses to the Shockley-Haynes experiments [1]–[2]. The voltage applied between two tungsten probes creates an electric field moving optically induced excess carriers. Two additional probes connected to oscilloscope allow us to visualize the dynamics of injected clouds of electrons and holes. The moving velocity and width of the peak of excess carries cloud being measured provides information about diffusivity and thus mobility of carriers. The major results are recorded on the oscilloscope where a cloud of excess carriers was examined. Subtracting contribution of excess carriers from total measured current defines conductivity of the tested material, i.e., natural doping of the material. Current study is the first phase of the development performed on single layer of material. Even for simple solar cell p-n junction the light absorbing layer should be carefully defined. Selection of variable wavelength lights for multilayered solar cell structures is the task for our continued study.