Study of the effect of excess carrier lifetime depth profiles and depth dependent absorption coefficients on the emitted photoluminescence spectrum of chalcopyrite thin films

The emitted photoluminescence (PL) resulting from radiative recombination in semiconductors is strongly governed by excess carrier density, which is influenced by excess carrier lifetime, absorption coefficient and according boundary conditions at front and rear contact. We have numerically solved the diffusion equation for the excess carrier density with depth dependent lifetime profiles (originating from a depth dependent defect density) and depth dependent absorption coefficient (originating from a depth dependent band‐gap) using a residual control based boundary value problem solver. The emitted PL from the absorber has been calculated on the basis of the excess carrier density with a 1D‐matrix transfer formalism including propagation, multireflection at phase boundaries and reabsorption of PL‐photons. For different lifetime or absorption depth profiles we have characterized the influence on the excess carrier depth profile as well as on the resulting spectral PL yield. Finally the calculated PL spectra were compared to the quasi‐Fermi level splitting from the excess carriers to show the influence of both depth profiles on the shape of the photoluminescence spectrum. Copyright © 2010 John Wiley & Sons, Ltd.