Abstract
Cu
2
ZnSnS
4
(CZTS) is an attractive material for thin film solar cells because all its constituents are Earth-abundant elements, and it’s a direct transition semiconductor with a band gap ...energy of 1.5 eV that is suitable for absorbing solar light spectrum effectively. CZTS is generally formed by precursor formation followed by heat treatment at 500 °C–600 °C to enhance the growth of crystal grain. In this work, a novel CZTS crystal grain re-growth process using post-laser annealing was investigated. 445 nm wavelength laser irradiation was performed on the Al-doped ZnO/CdS/CZTS/Mo/substrate stacked structure. X-ray diffraction and scanning microscope showed the CZTS crystal grain enlargement. Solar cells were fabricated on those structures and the external quantum efficiency was found to be improved especially at 500–1000 nm wavelength light absorption. That resulted in a short circuit current improvement.
Cu2Sn1-xGexS3 (CTGS) is a compound composed of relatively abundant elements in the crust of the earth. The band gap of CTGS can be tuned by substituting elements at the Sn and Ge sites, making it an ...attractive material for low-environmental-impact solar cells. In this study, CTGS thin films were fabricated with a controlled Ge/(Ge + Sn) composition ratio (x) by combining the co-evaporation method and sulfurization in an infrared furnace. Furthermore, the effect of Na on the CTGS and changes in the solar cell properties were investigated by stacking and sulfurizing NaF on the precursor fabricated using the co-evaporation method. As a result, CTGS with varying x was successfully fabricated by varying the deposition time of the Cu2GeS3 layer using co-evaporation. Additionally, CTGS prepared by doping with Na showed enlarged CTGS crystals compared to Na-free CTGS. The fabricated CTGS solar cells achieved a power conversion efficiency of more than 4.5% after doping with Na.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
Cu
2
ZnSnS
4
(CZTS) is interesting as a light absorption layer for thin-film solar cells because it consists of only earth-abundant materials such as copper, zinc, tin, and sulfur. The poor ...adhesion between CZTS and molybdenum (Mo), which is the back metal contact material, causes CZTS to peeling off during the chemical bath deposition (CBD) for the formation of CdS as a buffer layer. This induces severe degradation of the solar cell performance. In this study, we investigated the effect of annealing following back contact metal layer formation on CZTS stability and solar cell performance. By annealing Mo/soda lime glass at 400 °C in atmosphere, Mo was oxidized, and the surface roughness of Mo increased. On the Mo surface, the CZTS peeling off was suppressed during the CBD process, resulting in an improvement in the shunt resistance.
Abstract
Cu
2
ZnSnS
4
(CZTS) is a promising material for solar cells because all its constituents are earth-abundant elements, and its light absorption coefficient is ∼100 times higher than that of ...Si. CZTS is generally formed by precursor formation followed by heat treatment at 400 °C–600 °C. In this work, a novel CZTS formation process, which consists of Cu-Zn-Sn-S containing CZTS precursor formation followed by 445 nm laser irradiation in atmosphere, is investigated. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and UV–vis spectroscopy analysis reveals that the poly crystallization of CZTS precursor is promoted by increasing the output power or scan time per unit length at the laser irradiation. This suggests that the defect or secondary phase reduces, and the precursor changes to CZTS polycrystal by laser annealing. Finally, a CZTS thin-film solar cell is fabricated through laser annealing, with an efficiency of 0.003% under AM1.5 G (100 mW cm
−2
) at 25 °C.
The dependence of photoluminescence (PL) on sulfurization temperature of the Cu
2
SnS
3
(CTS) thin films was investigated. CTS thin films were prepared at various sulfurization temperatures in the ...range of 500–600 ℃, and differences in the conversion efficiency of solar cells with the CTS thin films as absorption layer and the crystal structure of the CTS thin films were observed. In low-conversion-efficiency CTS films, which were a mix of monoclinic and cubic crystals, the PL spectrum only showed donor–acceptor pair (DAP) recombination luminescence due to deep defects. In high-conversion-efficiency CTS thin films, which contained only monoclinic crystals, the PL spectrum showed DAP recombination luminescence originating from the same deep defects. In addition band-edge luminescence was observed at room temperature. Thus, it was found that the conversion efficiency and crystal structure of CTS thin film can be easily estimated from PL measurements.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
