Semiconductor Physics, Quantum Electronics & Optoelectronics, 20 (4), P. 418-423 (2017).

Macroscopic versus microscopic photovoltaic response of heterojunctions based on mechanochemically prepared nanopowders of kesterite and n-type semiconductors
O.P. Dimitriev1, D.O. Grynko1, A.M. Fedoryak1, T.P. Doroshenko1, M. Kratzer2, C. Teichert2, Yu.V. Noskov3, N.A. Ogurtsov3, A.A. Pud3, P. Balaz4, M. Balaz4, M. Tesinsky4

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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