Effects of ammonia concentration on morphology, composition and optical properties of ZnO_1-xS_x thin films of Cu(In, Ga)Se₂ solar cells

Abstract

ZnO_1-xS_x films were prepared by chemical bath deposition (CBD) on glass substrate. The effects of ammonia concentration on the structure characteristics of ZnO_1-xS_x films were studied. The results of scanning electron microscope (SEM) show that the film has good density when the concentration of ammonia is 0.4 M. Because more S^2- ions are involved in the reaction and less precipitates are generated, the film is relatively dense. The distribution of the film element shows that the growth rate of the film first accelerates and then slows down as the concentration of ammonia increases. X-ray diffraction (XRD) study shows that the diffraction peak is obvious when the ammonia concentration is 0.4 M, and the crystallinity of the film is good. Ultraviolet (UV) spectrophotometer test results show that the ratio of S content (x) and optical band gap (E_g) satisfies E_g(x)=3.325 7x²−2.718 7x+4.357 6. Increasing S content can increase the optical band gap of the film, and increasing ammonia concentration can improve the absorbance of the film, but both have good transmittance. At the ammonia concentration of 0.4 M, the absorbance of the film is good in the wavelength range of 300–900 nm, the transmission rate reaches 80%, and the band gap is 3.75 eV, which is suitable for the buffer layer of solar cells.

References

[1] MaJ, TangK, MaoH, et al.. Behavior and impact of sulfur incorporation in zinc oxysulfide alloy grown by metal organic chemical vapor deposition[J]. Applied surface science, 2018, 435: 297-304

[2] KhemiriN, AousgiF, KanzariM. Tunable optical and structural properties of Zn(S,O) thin films as Cd-free buffer layer in solar cells[J]. Materials letters, 2017, 199: 1-4

[3] ZellaguiR, DehdouhH, AdnaneM, et al.. Cd_xZn_1-xS thin films deposited by chemical bath deposition (CBD) method[J]. Optik, 2020, 207: 164377

[4] BaeD, GhoJ, ShinM, et al.. Effect of zinc addition on properties of cadmium sulfide layer and performance of Cu(In,Ga)Se₂ solar cell — ScienceDirect[J]. Thin solid films, 2013, 535(20):162-165

[5] DeulkarS H, HuangJ L, Neumann-SpallartM. Zinc oxysulfide thin films grown by pulsed laser deposition[J]. Journal of electronic materials, 2010, 39(5):589-594

[6] ChengQ, WangD, ZhouH. Electrodeposition of Zn(O,S) (zinc oxysulfide) thin films: exploiting its thermodynamic and kinetic processes with incorporation of tartaric acid[J]. Journal of energy chemistry, 2017, 27(3):S2095495617302474

[7] FanY, LiX D, LinS P, et al.. Preparation of Zn(O,S) thin films with magnetron sputtering method and application in CIGS solar cell[J]. Journal of synthetic crystals, 2017, 46(6): 996-1001

[8] WuW, ShenH, ChenJ, et al.. Impact of thiourea concentration on the properties of sol-gel derived Zn(O,S) thin films and Cu(In,Ga)Se₂ solar cells[J]. Journal of sol-gel science and technology, 2018, 86(2):266-273

[9] LinX, LiH, QuF, et al.. Cu(In,Ga)Se₂ solar cell with Zn(S,O) as the buffer layer fabricated by a chemical bath deposition method[J]. Solar energy, 2018, 171: 130-141 SEP.)

[10] BuffiereM, GautronE, HildebrandtT, et al.. Composition and structural study of solution-processed Zn(S,O,OH) thin films grown using H₂O₂ based deposition route[J]. Thin solid films, 2013, 535(may15):171-174

[11] YaoH, ShenH, ZhuX, et al.. Influence of Cd source concentration on photo-current response property of Cd_xZn_1-xS film prepared by chemical bath deposition[J]. Ceramics international, 2015, 42(2):2466-2471