Transients in p-n-junction solar cells

Abstract

Expressions for transient photocurrents and photovoltages are derived by solving the time-dependent diffusion equation for both horizontal- and vertical-junction cells. Four cases are dealt with: (i) when the light is switched off at t=0; (ii) when the light is switched on at t=0; (iii) when the cell is illuminated by a square pulse of finite duration; (iv) when it is illuminated by a delta pulse. Assuming certain values for the parameters of the material of the cell, numerical results are reported for conventional cells of diffused layer thickness 0.5 and 5 mu m and one vertical-junction cell. The use of such studies for measurement of life times and diffusion lengths of carriers is suggested.