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Atomic layer grown zinc–tin oxide as an alternative buffer layer for Cu2ZnSnS4-based thin film solar cells: influence of absorber surface treatment on buffer layer growth

DOI: 10.1021/acsaem.2c02579 DOI Help

Authors: Natalia M. Martin (Uppsala University) , Tobias Torndahl (Uppsala University) , Melike Babucci (Uppsala University) , Fredrik Larsson (Uppsala University) , Konstantin Simonov (Uppsala University; Swerim AB) , Dorotea Gajdek (Malmö University) , Lindsay R. Merte (Malmö University) , Hakan Rensmo (Uppsala University) , Charlotte Platzer-Bjorkman (Uppsala University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Energy Materials

State: Published (Approved)
Published: October 2022
Diamond Proposal Number(s): 21742

Open Access Open Access

Abstract: Zn1–xSnxOy (ZTO) deposited by atomic layer deposition has shown promising results as a buffer layer material for kesterite Cu2ZnSnS4 (CZTS) thin film solar cells. Increased performance was observed when a ZTO buffer layer was used as compared to the traditional CdS buffer, and the performance was further increased after an air annealing treatment of the absorber. In this work, we study how CZTS absorber surface treatments may influence the chemical and electronic properties at the ZTO/CZTS interface and the reactions that may occur at the absorber surface prior to atomic layer deposition of the buffer layer. For this, we have used a combination of microscopy and synchrotron-based spectroscopies with variable information depths (X-ray photoelectron spectroscopy, high-energy X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy), allowing for an in-depth analysis of the CZTS near-surface regions and bulk material properties. No significant ZTO buffer thickness variation is observed for the differently treated CZTS absorbers, and no differences are observed when comparing the bulk properties of the samples. However, the formation of SnOx and compositional changes observed toward the CZTS surface upon an air annealing treatment may be linked to the modified buffer layer growth. Further, the results indicate that the initial N2 annealing step integrated in the buffer layer growth by atomic layer deposition, which removes Na–COx species from the CZTS surface, may be useful for the ZTO/CZTS device performance.

Journal Keywords: kesterite CZTS; ALD ZTO; interface characterization; N2 annealing; XPS; HAXPES; XAS

Diamond Keywords: Photovoltaics; Semiconductors

Subject Areas: Materials, Physics, Energy

Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: GALAXIES at Soleil; P64 at DESY

Added On: 17/10/2022 08:27


Discipline Tags:

Surfaces Earth Sciences & Environment Sustainable Energy Systems Energy Physics Climate Change Physical Chemistry Energy Materials Chemistry Materials Science Chemical Engineering interfaces and thin films Engineering & Technology

Technical Tags:

Spectroscopy X-ray Photoelectron Spectroscopy (XPS) Hard X-ray Photoelectron Spectroscopy (HAXPES)