Meng Cao a, Zhen Xu a, Weifan He a, Zhenzhao Zhang a, Zexin Wang a, Qingzhi Hu a, Jian Huang a, Linjun Wang a b c
a
School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China
b
Zhejiang Institute of Advanced Materials, SHU, Jiashan 314113, China
c
Shanghai Collaborative Innovation Center of Intelligent Sensing Chip Technology, Shanghai, China
## Abstract
CdZnTe (CZT), as an optimum absorption layer, has many attractive characteristics for photoelectrochemical (PEC) water splitting, such as tunable band gaps (1.45–2.26 eV) and high absorption coefficient (≥104 cm−1). The addition of Se into CZT was found to be very effective in arresting the formation of sub-grain boundaries, improving compositional homogeneity. In this paper, CZT films were deposited on fluorine-doped tin oxide-coated (FTO) substrates by close-spaced sublimation method. The influence of selenization process to the structural, morphological, and optical properties of CZT films was studied. The phase purity properties of CdZnTeSe (CZTS) films were analyzed by X-ray diffraction (XRD), energy disperse spectroscopy (EDS) and Raman spectra measurements. The morphological characteristics of CZTS films were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The PEC properties of CZTS films were also investigated, which indicated that the photocurrents of CZTS films were greatly increased than that of as-deposited CZT films. The mechanism of PEC enhancement of CZTS films were studied detailedly.
Graphical abstract
## Introduction
As a group II−VI ternary semiconductors, Cd1-xZnxTe (CZT) is available in its high resistivity form (1010–1011 Ω•cm) as a highly compensated semiconductor. Its band gap can be tailored to the desired application by forming a continuous series of solid solutions of CdTe and ZnTe. A few percent Zn in CZT increases the energy of defect formation and its mechanical strength [1], [2]. CZT has been widely used in radiation detector, photovoltaic, X-ray imaging, light emitting diodes and other optoelectronic devices applications [3], [4], [5], [6]. CZT semiconductor nuclear detectors can operate at room temperature and they have several advantages. For example, they can be fabricated as portable devices and they can reduce the production and operational costs of the detection system [4]. They are also contributive to the remote battery-operated deployment applications. Beside these, more and more attention has been paid to study the photoelectric response of CZT films in recent years [7]. It is because of that the development of new energy technologies has attracted widespread attention from governments and researchers due to the depletion of fossil fuels [8]. Compared with nuclear energy, geothermal energy and marine energy technologies, solar energy technology have also been studied detailedly and achieved rapid development in recent decades. Various new photoelectric materials and related devices have been studied. Among these, the PEC properties of CdTe and CZT films have attracted great attention recently [7], [9].
Even though CZT based photoelectric devices have achieved great progress over the past years, there is still some problems that impede their development [7], [10]. For example, defects inside CZT can trap charges generated by absorption of radiation, thus limit the charge transport abilities of the detector and result in lowering its performance for precise measurements of X-ray and gamma-ray energies [11], [12]. Defects in CZT are mainly Te inclusions, subgrain boundaries, and compositional nonuniformity and so on. Studies indicates that introducing some Se into CZT can make obvious changes, which can increase compositional uniformity, decrease Te inclusions and subgrain boundary network [13], [14], [15]. Compositional homogeneity can increase the overall yield of detector-grade material of CZTS [12]. The decreasing of defects inside CZTS is contributive to enhance the spatial charge transport uniformity inside the detector structure. Then it is easy to fabricate high-quality detectors and decrease the cost of high-resolution devices. However, the PEC properties of CZTS have never been reported. Then, CZT films are deposited with closed-space sublimation (CSS) method in this paper. CZTS films can be achieved by annealing process in Se atmosphere [15], [16], [17]. The structural, morphological, optical and PEC properties of CZTS films have been studied. The research work is contributive to the development of CZTS based photoelectric devices.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/enhanced-photoelectrochemistry-properties-of-cdzntese-thin-films.html