Bandgap Tunable Ternary Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ Nanocrystals for Solar Cell Applications

Journal Article · 27 December 2019 · ACS Omega

DOI: https://doi.org/10.1021/acsomega.9b01762 · OSTI ID:1580545

Boon-on, Patsorn ^[1]; Singh, David J.  ^[2]; Shi, Jen-Bin ^[3]; Lee, Ming-Way  ^[1]

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1. National Chung Hsing Univ., Taichung (Taiwan). Inst. of Nanoscience and Dept. of Physics
2. Univ. of Missouri, Columbia, MO (United States). Dept. of Physics and Astronomy
3. Feng Chia Univ., Taichung (Taiwan). Dept. of Electronic Engineering

We report the synthesis and photovoltaic performance of a new nonstoichiometric ternary metal sulfide alloyed semiconductor—Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ nanocrystals prepared by the two-stage sequential ionic layer adsorption reaction technique. The synthesized Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ nanocrystals retain the orthorhombic structure of the host Sb₂S₃ with Cd substituting a fraction ($$x$$ = 0–0.15) of the cationic element Sb. The Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ lattice expands relative to the host, Sb₂S₃, with its lattice constant $$a$$ increasing linearly with Cd content $$x$$. Optical and external quantum efficiency (EQE) spectra revealed that the bandgap $$E_g$$ of Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ decreased from 1.99 to 1.69 eV (i.e., 625–737 nm) as $$x$$ increased from 0 to 0.15. Liquid-junction Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ quantum dot-sensitized solar cells were fabricated using the polyiodide electrolyte. The best cell yielded a power conversion efficiency (PCE) of 3.72% with the photovoltaic parameters of $$J_{sc}$$ = 15.97 mA/cm², $$V_{oc}$$ = 0.50 V, and FF = 46.6% under 1 sun. The PCE further increased to 4.86%, a respectable value for a new solar material, under a reduced light intensity of 10% sun. The PCE (4.86%) and $$J_{sc}$$ (15.97 mA/cm²) are significantly larger than that (PCE = 1.8%, $$J_{sc}$$ = 8.55 mA/cm²) of the Sb₂S₃ host. Electrochemical impedance spectroscopy showed that the ZnSe passivation coating increased the electron lifetime by three times. The EQE spectrum of Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ has a maximal EQE of 82% at $$λ$$ = 350 nm and covers the spectral range of 300–750 nm, which is significantly broader than that (300–625 nm) of the Sb₂S₃ host. The EQE-integrated current density yields a $$J_{ph}$$ of 11.76 mA/cm². The tunable bandgap and a respectable PCE near 5% suggest that Cd$$_x$$Sb$$_{2–y}$$S$$_{3-δ}$$ could be a potential candidate for a solar material.

• Research Organization: National Chung Hsing Univ., Taichung (Taiwan); Univ. of Missouri, Columbia, MO (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; Ministry of Science and Technology of the Republic of China (MOST)
• Grant/Contract Number: SC0019114; 107-2112-M-005-007
• OSTI ID: 1580545
• Alternate ID(s): OSTI ID: 1583098; OSTI ID: 1591987
• Journal Information: ACS Omega, Vol. 5, Issue 1; ISSN 2470-1343
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English