Berlin 2015 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 30: Photovoltaics: Nanostructured materials

HL 30.2: Talk

Tuesday, March 17, 2015, 10:30–10:45, ER 164

Investigation of the Spatial-Dependent Charge Carrier Collection Probability in CuInS₂/ZnO Colloidal Quantum Dot Solar Cells — •Dorothea Scheunemann, Sebastian Wilken, Jürgen Parisi, and Holger Borchert — University of Oldenburg, Department of Physics, Energy and Semiconductor Research Laboratory, 26111 Oldenburg

Colloidal quantum dot (CQD) solar cells with solution-producible absorber layers have made rapid progress in the last few years. In particular, the so-called depleted-heterojunction concept, consisting of a wide band gap n-type semiconductor and a p-type CQD film as absorber, appears promising. As an alternative to the commonly used but highly toxic Pb chalcogenide materials, we recently reported on the successful utilization of CuInS₂ nanocrystals as absorber layer in CuInS₂/ZnO heterojunction solar cells [1]. However, to date, the efficiency of these devices remained limited compared to state-of-the-art Pb-based CQD solar cells. To investigate possible limitations of the CuInS₂/ZnO system, we modeled the spatially and spectrally resolved absorption in the individual layers of the device stack using the transfer-matrix method. Here, we present a simple method to extract a spatial-dependent charge carrier collection efficiency based on the reconstruction of external quantum efficiency measurements using the modeled absorption profiles. With the help of this analysis, we identified a substantial “dead zone” in our devices, where the collection probability of excess carriers is dramatically reduced.

[1] D. Scheunemann et al., Appl. Phys. Lett. 103, 133902 (2013).