Berlin 2005 – scientific programme

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HL: Halbleiterphysik

HL 56: Photovoltaik I

HL 56.1: Talk

Tuesday, March 8, 2005, 15:00–15:15, TU P-N202

Voltage dependent series resistance of thin film Cu(In, Ga)Se₂ solar cells — •Osama Tobail and Juergen Werner — Pfaffenwaldring 47, D-70569 Stuttgart, Germany

Series resistance R_s and ideality factor n_id deteriorate the performance of solar cells. Usually, we measure the dark current(I)/voltage(V)-curves and determine R_s and the n_id from a plot of conductance(G)/current(I) versus conductance(G) [1]. However, in the case of Cu(In, Ga)Se₂ (CIGS) this plot is curved, indicating that R_s decreases with increasing V. In order to investigate this V-dependence in details, we use a series of samples with different thicknesses of the CdS-buffer and the CIGS-absorber. The ideality factor n_id from the dark I/V-curve depends on the buffer thickness and correlates with the V-dependence of R_s. An analysis of the illuminated I/V-curves at different illumination levels is particularly suitable to investigate the voltage dependent R_s in more details. The series resistance R_s consists of two parts: One part is independent of V, the other part decays exponentially with V. This voltage dependence of R_s is the result of a voltage dependent charge at the grain boundaries of the polycrystalline CIGS solar cells.

[1] J. H. Werner, Appl. Phys. A47, 291 (1988).