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HL: Fachverband Halbleiterphysik

HL 90: Inhomogeneous Materials for Solar Cells

HL 90.4: Vortrag

Freitag, 24. März 2017, 12:15–12:30, POT 81

Effect of buffer layer cations on absorber dopant profiles of Cu(In,Ga)Se2 thin film solar cells — •Florian Werner, Michele Melchiorre, Hossam Elanzeery, and Susanne Siebentritt — Laboratory for Photovoltaics, Physics and Materials Science Research Unit, University of Luxembourg, 41 rue du Brill, L-4422 Belvaux, Luxembourg

The correct interpretation of apparent dopant profiles obtained by capacitance-based techniques on chalcopyrite thin film solar cell absorbers is still debated. We have recently shown that Cd in-diffusion into the absorber might in part explain the observed dopant profiles. We expand on this study by comparing frequency-dependent capacitance-voltage measurements of different buffer/window stacks, e.g. CdS/ZnO, Zn(O,S)/ZnO, and MgF2, on the same absorber. Deconvolution of the measured impedance spectra allows to separate the capacitance of the main junction from parasitic elements. We find parasitic capacitances which agree reasonably well with the geometric capacitance of the respective buffer layer. Dopant profiles constructed from the extracted voltage-dependent junction capacitance exhibit significant differences between different buffer/window configurations and are consistent with cation in-diffusion reducing the surface-near acceptor concentration. This in-diffusion gives rise to a depth-dependent dopant profile and is more pronounced for Cd than for Zn. The MgF2 layer in contrast appears to be stable and we obtain depth-independent dopant concentrations close to 1017 cm-3, comparable to the free hole concentration obtained by Hall measurements on similar absorbers.