Effect of Impurity Concentration Gradient on the Collection of Charge Carriers in the p-n Junction based Solar Cells

Abstract An effective method for increasing the mean free path of light charge carriers in p-n junction solar cells is discussed. It is shown that by regulating the doping process of the light-absorbing emitter part of the solar cell and creating non-uniform distribution of the doping impurity in it, it is possible to increase the diffusion length of minority charge carriers. As a result, recombination losses decreases, the number of minority charge carriers passing through the p-n junction increases, the collection of photogenerated carriers increases, and consequently energy conversion efficiency increases. It is also shown that the stronger and greater the curvature of the impurity distribution in the illuminated p-emitter of a p-n solar cell, the greater the change in the diffusion coefficient. Estimates show that with a difference of four orders of magnitude in the concentration of doping acceptors (from 10 18 to 10 14 cm-3) in the emitter, the diffusion constant of minority carriers increases almost 3.1 times.