Ternary Cu₂SnS₃: Synthesis, Structure, Photoelectrochemical Activity, and Heterojunction Band Offset and Alignment

Abstract

Ternary Cu 2 SnS 3 (CTS) is an attractive nontoxic and earth-abundant absorber material with suitable optoelectronic properties for cost-effective photoelectrochemical applications. Herein, we report the synthesis of high-quality CTS nanoparticles (NPs) using a low-cost facile hot injection route, which is a very simple and nontoxic synthesis method. The structural, morphological, optoelectronic, and photoelectrochemical (PEC) properties and heterojunction band alignment of the as-synthesized CTS NPs have been systematically characterized using various state-of-the-art experimental techniques and atomistic first-principles density functional theory (DFT) calculations. The phase-pure CTS NPs confirmed by X-ray diffraction (XRD) and Raman spectroscopy analyses have an optical band gap of 1.1 eV and exhibit a random distribution of uniform spherical particles with size of approximately 15–25 nm as determined from high-resolution transmission electron microscopy (HR-TEM) images. The CTS photocathode exhibits excellent photoelectrochemical properties with PCE of 0.55% (fill factor (FF) = 0.26 and open circuit voltage (Voc) = 0.54 V) and photocurrent density of −3.95 mA/cm 2 under AM 1.5 illumination (100 mW/cm 2 ). Additionally, the PEC activities of CdS and ZnS NPs are investigated as possible photoanodes to create a heterojunction with CTS to enhance the PEC activity. CdS is demonstrated to exhibit a higher current density than ZnS, indicating that it is a better photoanode material to form a heterojunction with CTS. Consistently, we predict a staggered type-II band alignment at the CTS/CdS interface with a small conduction band offset (CBO) of 0.08 eV compared to a straddling type-I band alignment at the CTS/ZnS interface with a CBO of 0.29 eV. The observed small CBO at the type-II band aligned CTS/CdS interface points to efficient charge carrier separation and transport across the interface, which are necessary to achieve enhanced PEC activity. The facile CTS synthesis, PEC measurements, and heterojunction band alignment results provide a promising approach for fabricating next-generation Cu-based light-absorbing materials for efficient photoelectrochemical applications.

Effects of Preparation Procedures and Porosity on Thermoelectric Bulk Samples of Cu2SnS3 (CTS)

“…The unfilled Cu-3d orbitals introduce holes in the CTS system, making it a p-type semiconductor. CTS components are earth-abundant, eco-friendly, non-toxic, non-hazardous, and have low formation energies; therefore, they are explored for various applications, such as TE [7], photovoltaic [8], optoelectronics [9], photoelectrochemical [10], and supercapacitors [11], just to name a few. CTS has attracted the TE community for its remarkable crystallographic structures with different degrees of cation-disorder, which helps in the suppression of thermal conductivity to an ultra-low level, without much hindrance to the electronic transport, also known as the so-called "phonon-glass-electron-crystal (PGEC)" behavior.…”

Hydrothermally synthesized nanocrystalline photoactive SnS2 thin films: effect of surface directing agents

“…In this plot, when the middle region of frequency moves to a lower frequency region, the electron has a shorter life span. 65,66 The reason behind this might be the effect of surfactants on film growth. The data obtained from the study of the bode phase are shown in Table 4 and Fig.…”

Effect of the stacking order, annealing temperature and atmosphere on crystal phase and optical properties of Cu2SnS3

“…The ternary copper tin sulfide family (Cu x SnS y ) includes Cu 2 SnS 3 , Cu 3 SnS 4 , Cu 4 SnS 4 , Cu 2 Sn 3 S 7 and Cu 7 Sn 3 S 8 9 , 10 crystalline compounds, and some of them are also regarded as a potential absorber layers for thin film solar cells (TFSC). Among these compounds, Cu 2 SnS 3 (CTS) has attracted particular attention due to its potential to be used as small band semiconductors for infrared photodetectors, but also for photocatalytic, optoelectronic, and supercapacitor applications 11 – 16 . CTS is also regarded as a precursor for the synthesis of CZTS materials used in solar cells devices 17 , 18 .…”