Recently simple binary and ternary semiconductors such as AgBiS2, CuSbS2, CuSbSe2, PbS, SnS, Sb2S3, and Sb2Se3 have attracted intensive attention as a low-cost and stable light absorbing materials. Among them, Sb2Se3 binary chalcogenide compound is considered to be a promising photovoltaic material due to their relatively low toxicity, long term stability, and earth abundant element availability. Sb2Se3 in its crystalline form has a proper bandgap (1.17 eV), high absorption coefficient, good band alignment in combination with various electron transport materials, and intrinsically benign grain boundaries because of its peculiar one-dimensional crystal structure. It can also be easily deposited by different methods such as thermal evaporation, sputtering, and atomic layer deposition (ALD). The most widely used method is evaporation due to its simplicity, but in the case of evaporation process, it is difficult to prevent the formation of Se-vacancy (VSe) because Se has high vapor pressure during the deposition process of Sb2Se3.
In our previous work, we have demonstrated that the ALD method inhibited the formation of defects in Sb2S3 and thus planar solar cells using ALD Sb2S3 absorber showed high efficiency with good reproducibility. Therefore, in this work, we have tried to deposit Sb2Se3 thin films by using plasma enhanced atomic layer deposition (PEALD), which was proceeded by the reaction of tetrakis(dimethylamino)antimony (TDMASb) and diethylselenide (DESe) at low temperature (120 °C). TDMASb is one of the most perspective general precursors for the ALD of antimony chalcogenide compound. DESe is also a commonly used Se precursor to substitute a highly toxic H2Se precursor. We observed the deposition rate, crystalline structure, morphology, chemical composition, and impurity of Sb2Se3 thin films prepared by PEALD. Uniformly deposited ALD Sb2Se3 thin films were applied to the superstrate solar cells with the structure of ITO/CdS/ALD Sb2Se3/Au and we have investigated the possibility of ALD Sb2Se3 as a photovoltaic absorber.
This work was supported by the DGIST R&D Programs of the Ministry of Science, ICT & Future Planning of Korea (17-BD-05).