Improvement of CZTSSe film quality and superstrate solar cell performance through optimized post-deposition annealing

Abstract

Improving the performance of kesterite solar cells requires high-quality, defect-free CZTS(Se) films with a reduced number of secondary phases and impurities. Post-annealing of the CZTS films at high temperatures in a sulfur or selenium atmosphere is commonly used to improve the quality of the absorbing material. However, annealing at high-temperatures can promote material decomposition, mainly due to the loss of volatile elements such as tin or sulfur. In this work, we investigate how the additional step of sulfurization at reduced temperatures affects the quality and performance of CZTSSe based solar cells. A comprehensive structural analysis using conventional and high resolution XRD as well as Raman spectroscopy revealed that the highest CZTSSe material quality with the lowest structural disorder and defect densities was obtained from the CZTS films pre-sulfurized at 420 °C. Furthermore, we demonstrate the possibility of using Sb2Se3 as a buffer layer in the superstrate configuration of CZTSSe solar cells, which is possible alternative to replace commonly employed toxic CdS as a buffer layer. We show that the additional low-temperature selenization process and the successful use of Sb2Se3 as a buffer layer could improve the performance of CZTSSe-based solar cells by up to 3.48%, with an average efficiency of 3.1%.

Cadmium‐Free Kesterite Thin‐Film Solar Cells with High Efficiency Approaching 12%

“…Compared to CdS-based devices, the devices with ZTO buffer layer showed better rectification characteristics indicating suppressed leakage current density. Moreover, we investigated diode performance parameters such as shunt conductance (G), series resistance (R), diode ideality factor (A), and reverse saturation current density (J 0 ) by Equation (1).…”

“…Kesterite (CZTSSe) thin film solar cells have received enormous attention owing to its outstanding properties such as higher absorption coefficient (>10 4 cm −1 ) in the visible spectrum, appropriate bandgap (1.0-1.5 eV), non-toxic nature, and earth-abundant constituent. [1][2][3] Therefore, CZTSSe-thin S), and (Zn, Sn)O have been used. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Among them, (Zn, Sn)O commonly known as "ZTO" is a propitious substitute due to its non-toxicity and promising results that have been reported previously by the ALD method.…”

“…Kesterite (CZTSSe) thin film solar cells have received enormous attention owing to its outstanding properties such as higher absorption coefficient (>10 4 cm −1 ) in the visible spectrum, appropriate bandgap (1.0–1.5 eV), non‐toxic nature, and earth‐abundant constituent. [ 1–3 ] Therefore, CZTSSe‐thin film solar cells have huge potential to replace the toxic and rare elements (Cd, In, Te, and Ga), for the sophisticated CdTe and Cu(In,Ga)Se 2 (CIGS) absorber. [ 4–5 ] The typical structure of CZTSSe devices, Mo/CZTSSe/CdS/ITO/Ag, is derived from CIGS solar cells, which have been put into commercial production.…”

Environment-friendly copper-based chalcogenide thin film solar cells: status and perspectives

“…120,121 Better morphology and excellent crystallinity of the CZTS layer can also reduce the detrimental secondary phase formation. 121,122…”

A Comprehensive Review on the Recent Strategy of Cation Substitution in CZTS(Se) Thin Films to Achieve Highly Efficient Kesterite Solar Cells

“…Notably, several endeavors have focused on fabricating Cd‐free CZTS‐based devices with highly stable superstrate architecture. [ 8–10 ] Introducing larger elements, such as Ag/Li for Cu, [ 11,12 ] Mn/Cd for Zn, [ 13,14 ] and Sn by other elements like Ge/Ti, [ 15,16 ] has shown to be an effective means to reduce Cu–Zn disorder and Sn‐related defects. Ag substitution, in particular, has become a common and successful strategy in suppressing Cu Zn defects in bulk CZTSSe, resulting in an improvement in device V OC .…”