Measurement of diffusion length in CuInSe2 and CdS by the electron beam induced current method

The minority‐carrier diffusion length Le for electrons in p‐CuInSe2 was determined by analyzing the magnitude of the electron beam induced current (EBIC) as a function of distance from the p/n junction in an n‐CdS/p‐CuInSe2 solar cell whose solar energy conversion efficiency was about 8%. Data obtained for electron beam energies of 10, 20, and 30 keV showed that Le was at least 0.92 μm. Analysis of the data in terms of a model in which the injection process is approximated by a point source results in a value of Le ∼2.5 μm and a surface recombination velocity of about 1.4×106 cm/sec on a as‐cut surface. The analysis leads to the inference that the ’’point source’’ is located at a depth equal to about 0.06 times the electron range below the surface on which the beam is incident.