Surface and allied studies in silicon solar cells

Measuring small-signal admittance versus frequency and forward bias voltage together with a new transient measurement apparently provides the most reliable and flexible method available for determining back surface recombination velocity and low-injection lifetime of the quasineutral base region of silicon solar cells. The new transient measurement reported here is called short-circuit-current decay (SCCD). In this method, forward voltage equal to about the open-circuit or the maximum power voltage establishes excess holes and electrons in the junction transition region and in the quasineutral regions. The sudden application of a short circuit causes an exiting of the excess holes and electrons in the transition region within about ten picoseconds. From observing the slope and intercept of the subsequent current decay, the base lifetime and surface recombination velocity can be determined. The admittance measurement previously mentioned then enters to increase accuracy particularly for devices for which the diffusion length exceeds the base thickness.