Thermal evaporation–deposited hexagonal CdS buffer layer with improved quality, enlarged band gap, and reduced band gap offset to boost performance of Sb2(S,Se)3 solar cells

• Published in: Journal of alloys and compounds Vol. 920; p. 165885
• Main Authors: Liu, Jingjing, Cao, Mengsha, Feng, Zhengdong, Ni, Xiaomeng, Zhang, Jing, Qiu, Jianhua, Zhang, Shuai, Guo, Huafei, Yuan, Ningyi, Ding, Jianning
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 05.11.2022; Elsevier BV
• Subjects: Antimony; Buffer layers; Cadmium sulfide; CdS thin film; Circuits; cubic phase; Energy gap; Evaporation; Fluorine; hexagonal phase; Open circuit voltage; Photovoltaic cells; Sb2(S,Se)3 solar cell; Short circuit currents; Solar cells; Substrates; Surface defects; Thick films; Tin oxides; CdS thin film; Sb2(S,Se)3 solar cell; cubic phase; hexagonal phase
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.165885

Chemical bath–deposited cadmium sulfide (CBD-CdS) is the most widely used buffer layer material for antimony selenosulfide (Sb2(S,Se)3) photovoltaic devices, but its medium band gap, large band gap offset with transparent conducting oxides, and surface defects must be addressed to improve its applicability. Hexagonal CdS films (60nm thick) prepared using the thermal evaporation method were used as the buffer layers of Sb2(S,Se)3 photovoltaic devices. Compared with CBD-CdS (60nm thick), thermal evaporation–deposited CdS (TED-CdS) films have a larger band gap and fewer surface defects. The Sb2(S,Se)3 film deposited on TED-CdS is more compact, and its 1D ribbons are stacked more vertically to the substrate. The band gap offset between CdS and fluorine-doped tin oxide glass decreases from 0.76eV (CBD-CdS) to 0.60eV (TED-CdS). Therefore, suppressed electron trap density and charge recombination, as well as improved light harvesting, are achieved. By replacing CBD-CdS with TED-CdS, the best device efficiency increases from 6.14% to 7.16%, with the open circuit voltage, short-circuit current density, and fill factor increasing from 0.660V, 15.96mA/cm2, and 58.37% to 0.664V, 17.39mA/cm2, and 62.85%, respectively. The device stability and reproducibility are also improved. [Display omitted] •Hexagonal CdS buffer layer was prepared by thermal evaporation (TED-CdS).•TED-CdS has larger band gap than chemical bath deposited CdS (CBD-CdS).•TED-CdS is conducive to the growth of [221]-oriented Sb2(S,Se)3 grains.•TED-CdS decreases the band gap offset between CdS and FTO.•Improved light harvesting and suppressed charge recombination are achieved.