Berlin 2018 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 6: Photovoltaics I
HL 6.12: Talk
Monday, March 12, 2018, 12:30–12:45, EW 203
Insight into local fluctuations of net doping and lifetime in Cu(In,Ga)Se2 solar cells — •Maximilian Krause1, Aleksandra Nikolaeva1, Jose Marquez1, Charles Hages1, Sergej Levcenko1, Thomas Unold1, Wolfram Witte2, Dimitrios Hariskos2, and Daniel Abou-Ras1 — 1Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany — 2Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Meitnerstr. 1, 70563 Stuttgart, Germany
It is known that local fluctuations in net doping and lifetime present in polycrystalline Cu(In,Ga)Se2 (CIGS) thin films (with [Ga]/[In]+[Ga]=0.33) can deteriorate the device performance of the corresponding solar cells via enhanced recombination. In order to investigate such fluctuations, electron-beam-induced current (EBIC) measurements were performed in a SEM on CIGS solar cells with different buffer layers: CdS, Zn(O,S), and In2S3 grown by chemical bath deposition. By fitting EBIC signals using appropriate models, the widths of the space-charge region, wSCR, and also the diffusion lengths of the minority charge-carriers, LD, were extracted. The order of magnitude of these values (400-500 nm and 1-2 µm) was verified by capacitance-voltage and quantum efficiency measurements. Although the values for wSCR and therefore the average net doping of the CIGS layers were the same in the solar cells with the different buffer layers, substantial local variations of wSCR were detected parallel to the p-n junction, which depend on the buffer/window stack applied. The present contribution discusses the impact of these fluctuations on the limitations of the device performance.