Experimental determination of vacuum-level band alignments of SnS-based solar cells by photoelectron yield spectroscopy

Abstract

Energy band offsets of SnS-based solar cell structure using various n-type semiconductors, such as CdS, SnS2, In2S3, ZnIn2Se4, ZnO, and Mg0.3In0.7O, are evaluated by photoelectron yield spectroscopy. The valence band discontinuities are estimated to be 1.6 eV for both SnS/CdS and SnS/SnS2, 0.9 eV for SnS/In2S3, 1.7 eV for SnS/ZnIn2Se4, and 1.8 eV for both SnS/ZnO and SnS/Mg0.3Zn0.7O. Using the valence band discontinuity values and the corresponding energy bandgaps of the layers, energy band diagrams are developed. This study implied a type-I heterostructure, appropriate for SnS-based solar cell, for the ZnIn2Se4 or MgxZn1−xO (0 ≤ x ≤ 0.3) interface and type-II for other junctions.

Fabrication of visible‐light transparent solar cells composed of NiO/NixZn1‐xO/ZnO heterostructures

“…The band gap energy was determined from optical absorbance measurements, which is obtained using a deuterium lamp in the UV region and a halogen lamp in the visible-light and near-infrared regions. We have revealed the band diagrams of SnS-related solar cells using PYS measurement [21]. …”

“…where Y is the photoelectron yield, hν is the photon energy, and I s is the photocurrent, as determined from a linear fit of the Y 1/3 versus hν plot [21,22]. To avoid the background photoelectron yield from the sample holder, aperture, and chamber, the signal measured from the sample was divided by the signal measured without the film.…”

Investigation of the sulfurization process of Cu2SnS3 thin films and estimation of band offsets of Cu2SnS3‐related solar cell structure

“…However, issues associated with fabrication/material costs and safety remain unresolved. In terms of material design for compound semiconductors, the most cost-effective, safe, and easily handled anions are sulfur and oxygen [2][3][4]. Ternary chalcogenide compound, Cu 2 SnS 3 (CTS), is a promising candidate as an earth-abundant absorber material [5].…”

“…In fact, the structure of CTS solar cells has not been extensively studied [6][7][8][9][10][11][12][13][14][15]. High-efficiency CIGS solar cells have typically been obtained by using CdS or zinccompounds as n-type buffer layers, which have the appropriate "spike" conduction-band offset [20][21][22][23]. The formation of an ideal pn-heterojunction, through the use of an appropriate n-type layer, is important for making high efficiency solar cells.…”

“…The flow and evaporation rates of the N 2 carrier gas and S source were 800 sccm and 40-50 μmol/min, respectively. The sulfurization equipment have been described elsewhere [2,3,24]. The ntype layers were deposited on the CTS layers for PYS measurements.…”