• 
  Babucci, M.; Törndahl, T.; Mukherjee, S.; Platzer Björkman, C.; Martin, N.M.: Studies of Atomic-Layer-Deposited Zn_1–XSn_XO_Y as an Alternative Buffer Layer for Cu₂Zn(Sn_1–X,Ge_X)S₄ Thin-Film Solar Cells. ACS Applied Electronic Materials 6 (2024), p. 7989-7999

10.1021/acsaelm.4c01317
Open Access version by external provider

Abstract:
Thin-film solar cells based on Cu2Zn(Sn1−X,GeX)S4 (CZTGS) absorbers are emerging technologies for solar energy conversion with low-cost, nontoxic components. In this work, we investigated CZTGS-based solar cells with varying Ge contents and an alternative buffer layer of Zn1–XSnXOY (ZTO) by atomic layer deposition. The results are compared to those of devices with the traditional CdS buffer layer. Overall, higher efficiency and open-circuit voltage (VOC) are observed for the devices with ZTO compared to those with the CdS buffer layer. Moreover, the results show that the CZTGS/ZTO device performance may further be improved by varying the ZTO properties (band gap or thickness) or by applying a surface treatment on the CZTGS absorber. An air annealing treatment of the chemically etched absorber surface improved the CZTGS device performance; however, nonetched devices show poor efficiency due to the presence of secondary phases (GeO2) at the absorber/buffer interface, shown by hard X-ray photoelectron spectroscopy measurements, as previously reported for the full-germanium Cu2ZnGeS4-based devices.