Reduction of interface recombination current for higher performance of p+-CZTSxSe(1-x)/p-CZTS/n-CdS thin-film solar cells using Kesterite intermediate layers. (1st July 2020)

• Record Type: Journal Article
• Authors: Enayati Maklavani, Shahin; Mohammadnejad, Shahram
• Is Part Of: Solar energy. Volume 204(2020)
• Page Start: 489
• Page End: 500
• Publication Date: 2020-07-01
• Subjects: Thin-film solar cell -- Interface recombination -- Conversion efficiency -- Open-circuit voltage -- Kesterite -- Intermediate layer; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2020.04.096
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: Comparison and validation of the simulation with the experimental result of Mo/CZTS/CdS/i-ZnO/ZnO:Al/Al thin-film solar cell. Introducing of CZTSe and CZTSSe intermediate layers (Mo/CZTSSe/CZTS/CdS/i-ZnO/ZnO:Al/Al) for the purpose of increasing efficiency and open-circuit voltage. Using the thin layers mentioned above and optimizing the structure as P + PN, the following efficiencies are respectively obtained: 15.98%, and 17.81%. In the proposed structure with CZTS0.2 Se0.8 intermediate layer, open-circuit voltage is increased to 986 mV by proper band alignment at back contact/CZTSSe interface and through reduction in series resistance recombination. Optimization of each of the two proposed structures to obtain the highest performance for the devices. Simulations demonstrate that at the bias voltage of 0.8 V for CZTSSe/CZTS structure, i.e. after employing the CZTS0.2 Se0.8 intermediate layer, the recombination current total density is acquired as 6.47 mA/cm 2 . Abstract: There have been significant efforts to enhance the performance of CZTS thin-film solar cells. However, the increase in series resistance, formation of the unfavorable MoS2 between the absorber layer and back-contact, and recombination losses are some of the most effective factors for the low values of the efficiency and open-circuit voltage parameters. In this paper, five experimental CZTS solar cells with high efficiency of 8.4–11% have been mainly studied and discussed. Afterwards, two experimental works have been reproduced to validate our results. Additionally, with introducing the thin CZTSx Se(1-x) layer between the Mo back-contact and CZTS absorber layer, the efficiency and open-circuit voltage of solar cells have been notably improved. There is a significant decrease in recombination losses (less than 12 mA/cm 2 ) after using CZTSx Se(1-x) intermediate layers between the absorber layer and back-contact. Using the CZTSe, and CZTS0.2 Se0.8 thin layers and optimizing the structure as p + pn structure (p + -CZTSx Se(1-x) /p-CZTS/n-CdS), the following efficiencies (and open-circuit voltage) are achieved as: 15.98% (921 mV) and 17.81% (986 mV), respectively. Simulations demonstrate that at 0.8-V bias for p + -CZTS0.2 Se0.8 /p-CZTS/n-CdS structure, the recombination current total density is reduced to 6.47 mA/cm 2 . To obtain the highest performance in the proposed structures, the absorber layer carrier concentration should be 1 × 10 16 cm −3 and the intermediate layer carrier concentration needs to be within the range of 1 × 10 17 cm −3 to 1 × 10 18 cm −3 . Furthermore, the optimum thickness of CZTSe and CZTSSe intermediate layers in the proposed structures is 50 nm.