Determination of the minority carrier lifetime in solar cells: A novel biased OCVD technique

A new simple method for the determination of the minority carrier lifetime (tau), based on a biased open circuit voltage decay (OCVD) technique, is an alyzed. In this case the excitation is given by a pulsed light source (time dependent contribution) added to a continuous background illumination (con tinuous forward bias). Under appropriate conditions this configuration prod uces an exponential voltage decay with a time constant which depends on the bias. This constant tends to an effective lifetime for the base region for large values of the bias voltage (typically, 400 to 500 mV). An inexpensiv e equipment has been developed. Measurements have been made on several crys talline silicon solar cells and on one high-efficiency neat-zone silicon so lar cell. Experimental results show good agreement with the theoretical mod el presented and with numerical PC-1D simulations.