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Limits and improvements of diffusion length determination by the constant short circuit current technique

: Warta, W.

Guimaraes, L.; Palz, W.; Reyff, C. de; Kiess, H.; Helm, P.:
Eleventh E.C. Photovoltaic Solar Energy Conference '92. Proceedings : International conference, held at Montreux, Switzerland, 12 - 16 October 1992
Chur: Harwood Academic Publishers, 1993 (EUR 14811/EN)
ISBN: 3-7186-5380-X
Photovoltaic Solar Energy Conference <11, 1992, Montreux>
Fraunhofer ISE ()
diffusion length; improvement; limit; quantum efficiency; SPV

The validity of the simple straight line evaluation of the base diffusion length from a plot of the inverse internal quantum efficiency versus light penetration depth is investigated by comparing the effective value deduced from simulated quantum efficiencies with the real diffusion length. Contributions from emitter and space charge region, surface recombination as well as multiple light reflection are included. Graphs of calculated errors in the obtained effective diffusion length are given for different sample thicknesses, rear surface recombination and reflectivity as well as different wavelength ranges. lt is found that in realistic devices with finite rear surface reflectivity large errors in the measured effective diffusion length are likely, the exact diffusion length is measured only accidently by an evaluation in the long wavelength range. On the other hand, diffusion lengths on the order of the sample thickness might be determined exactly. Comparing experimental with calcula ted curves in the proposed plot turns out to be a valuable tool for determining recombination parameters.