Abstract

The synthesis of (Cu,Ag)-Zn-Sn-S (CAZTS) and Ag-Zn-Sn-S (AZTS) nanocrystals (NCs) by means of “green” chemistry in aqueous solution and their detailed characterization by Raman spectroscopy and several complementary techniques are reported. Through a systematic variation of the nominal composition and quantification of the constituent elements in CAZTS and AZTS NCs by X-ray photoemission spectroscopy (XPS), we identified the vibrational Raman and IR fingerprints of both the main AZTS phase and secondary phases of Ag-Zn-S and Ag-Sn-S compounds. The formation of the secondary phases of Ag-S and Ag-Zn-S cannot be avoided entirely for this type of synthesis. The Ag-Zn-S phase, having its bandgap in near infrared range, is the reason for the non-monotonous dependence of the absorption edge of CAZTS NCs on the Ag content, with a trend to redshift even below the bandgaps of bulk AZTS and CZTS. The work function, electron affinity, and ionization potential of the AZTS NCs are derived using photoelectron spectroscopy measurements.

Highlights

  • Thin film solar cells based on Cu2 ZnSn(S,Se)4 (CZTSSe) absorber layers have gained increasing attention due to their suitable absorption spectrum, high absorption coefficient (104 –105 cm−1 ), and nontoxic earth-abundant components [1,2]

  • Based on our recent experience of successfully synthesizing CZTS NCs in water [33], we started a transition from the copper-based kesterite to the silver-based one through a series of mixed Cu1−x Agx ZnSnS4 (ACZTS) NCs using the same set of synthesis parameters

  • This is in agreement with previous reports on CZTS NCs obtained by the same synthesis route and indicates the formation of 3–4 nm kesterite NCs of good crystallinity [33]

Read more

Summary

Introduction

Thin film solar cells based on Cu2 ZnSn(S,Se) (CZTSSe) absorber layers have gained increasing attention due to their suitable absorption spectrum, high absorption coefficient (104 –105 cm−1 ), and nontoxic earth-abundant components [1,2]. Progress with improving cell efficiency has stopped at a value of about 13% since it has not been possible to further increase the open circuit voltage [3]. The latter problem is generally believed to originate from band tails caused by Cu-Zn antisite defects [4]. Many reports showed an improved lattice (cationic) order in (Cu1−x Agx ) ZnSn(S,Se) (CAZTS) or Ag2 ZnSn(S,Se) (AZTS), as well as a concomitant increase of the photovoltaic device efficiency [5,7,8], adverse effects of the substitution were reported [9].

Methods
Results
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.