¹V. Lashkaryov Institute of Semiconductor Physics of NAS of Ukraine, 45, prospect Nauky, 03680 Kyiv, Ukraine
²Institut für Physik, Montanuniversität Leoben, Franz-Josef-Straße 18, Leoben A-8700, Austria
³Institute of Bioorganic Chemistry and Petrochemistry, NAS of Ukraine, 50, Kharkivske Shose, 02160 Kyiv, Ukraine
⁴Institute of Geotechnics, Slovak Academy of Sciences, 45, Watsonova str., Kosice 04010, Slovakia

Abstract. Mechanochemically prepared nanopowder of selenium-free kesterite Cu2ZnSnS4 (CZTS) in combination with n-type semiconductors, i.e., CdS, ZnO and TiO2, was tested in planar and bulk-heterojunction solar cells. The samples have been studied by macroscopic current-voltage (I-V) measurements and Kelvin-probe atomic-force microscopy (KPFM). KPFM images taken under light illumination showed the distribution of the potential across the surface, with negative potential on the n-type semiconductor domains and positive potential on the CZTS domains, which indicated charge separation at the interface of the counterparts. The best result was found for the CdS-CZTS composition, which showed a potential difference between the domains up to 250 mV. These results were compared with the planar heterojunctions of CdS/CZTS and TiO2/CZTS, where CZTS nanopowder was pressed/deposited directly onto the surface of films of the corresponding n-type semiconductors. Again, I-V characteristics showed that cells based on CdS/CZTS heterojunctions have the best performance, with a photovoltage up to 200 mV and photocurrent densities up to 0.1 mA/cm2. However, the carrier generation was found to occur mainly in the CdS semiconductor, while CZTS showed no photo-response and served as the hole-transporting layer only. It is concluded that sensitization of the kesterite powder obtained by mechanochemical method is necessary to improve the performance of the corresponding solar cells.

Keywords: kesterite, cadmium sulphide, nanopowder, bulk heterojunction, photovoltaics.

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