Sb2Se3 Thin Film Solar Cells Research Articles

Efficiency enhancement of Sb2Se3 thin-film solar cells by the co-evaporation of Se and Sb2Se3

In this work, we present an alternative route to supply excessive selenium (Se) for the deposition of Sb2Se3 thin films by the co-evaporation of Se and Sb2Se3. Scanning electron microscopy (SEM) images showed that additional Se modified the growth process and surface morphology of Sb2Se3 thin films. X-ray diffraction (XRD) patterns confirmed that this co-evaporation process enhanced the beneficiary preferred orientations, and capacitance–voltage (C–V) measurement showed that the carrier concentration of the Sb2Se3 absorber increased with the additional evaporation of Se. Accordingly, the efficiency of the devices employing co-evaporated Sb2Se3 absorber layers increased significantly from 2.1 to 3.47% with a open-circuit voltage (VOC) of 364 mV, a short-circuit current density (JSC) of 23.14 mA/cm2, and a fill factor (FF) of 41.26%.

Ambient CdCl2 treatment on CdS buffer layer for improved performance of Sb2Se3 thin film photovoltaics

Antimony selenide (Sb2Se3) is appealing as a promising light absorber because of its intrinsically benign grain boundaries, suitable band gap (∼1.1 eV), strong absorption coefficient, and relatively environmentally friendly constituents. Recently, we achieved a certified 5.6% efficiency Sb2Se3 thin film solar cell with the assistance of ambient CdCl2 treatment on the CdS buffer layer. Here, we focused on investigating the underlying mechanism from a combined materials and device physics perspective applying current density-voltage (J-V) fitting analysis, atomic force microscope, X-ray photoelectron spectroscopy, fluorescence, and UV–Vis transmission spectroscopy. Our results indicated that ambient CdCl2 treatment on CdS film not only improved CdS grain size and quality, but also incorporated Cl and more O into the film, both of which can significantly improve the heterojunction quality and device performance of CdS/Sb2Se3 solar cells.

Optical properties of amorphous and polycrystalline Sb2Se3 thin films prepared by thermal evaporation

Sb2Se3 is a very promising photovoltaic material because of its attractive material, optical and electrical properties. Very recently, we reported a superstrate CdS/Sb2Se3 solar cell with 5.6% certified efficiency. In this letter, we focused on the optical properties of amorphous and polycrystalline Sb2Se3 thin films prepared by thermal evaporation. Using temperature dependent transmission spectrum and temperature dependent photoluminescence, the indirect optical transition nature and bandgap values as functions of temperature were acquired. Using ellipsometry measurements and Swanepoel's envelope method, the refractive indices as well as the dielectric constant in a wide wavelength range of 193–2615 nm were obtained. These works would lay the foundation for the further development of Sb2Se3 thin film solar cells.

Improving the performance of Sb2Se3 thin film solar cells over 4% by controlled addition of oxygen during film deposition

AbstractSb2Se3 has attracted great research interest very recently as a promising absorber material for thin film photovoltaics due to its suitable bandgap, high absorption coefficient, and non‐toxic, low cost, and earth abundant nature. In this work, a significant efficiency improvement to 4.8% of superstrate cadmium sulfide (CdS)/Sb2Se3 solar cells is obtained by the controlled addition of oxygen during thermal evaporation of Sb2Se3 films. Systematic materials and device physics characterization reveal that oxygen addition during Sb2Se3 film evaporation significantly improves the CdS/Sb2Se3 heterojunction quality through effective passivation of interfacial defect states, resulting in a substantial enhancement in device circuit voltage and short circuit current density. The 4.8% device is the highest efficiency thus far reported for Sb2Se3 thin film solar cells. Copyright © 2015 John Wiley & Sons, Ltd.

Thin-film Sb2Se3 photovoltaics with oriented one-dimensional ribbons and benign grain boundaries

Solar cells based on inorganic absorbers, such as Si, GaAs, CdTe and Cu(In,Ga)Se2, permit a high device efficiency and stability. The crystals’ three-dimensional structure means that dangling bonds inevitably exist at the grain boundaries (GBs), which significantly degrades the device performance via recombination losses. Thus, the growth of single-crystalline materials or the passivation of defects at the GBs is required to address this problem, which introduces an added processing complexity and cost. Here we report that antimony selenide (Sb2Se3)—a simple, non-toxic and low-cost material with an optimal solar bandgap of ∼1.1 eV—exhibits intrinsically benign GBs because of its one-dimensional crystal structure. Using a simple and fast (∼1 μm min–1) rapid thermal evaporation process, we oriented crystal growth perpendicular to the substrate, and produced Sb2Se3 thin-film solar cells with a certified device efficiency of 5.6%. Our results suggest that the family of one-dimensional crystals, including Sb2Se3, SbSeI and Bi2S3, show promise in photovoltaic applications. Materials with a one-dimensional crystal structure, such as antimony selenide, show considerable potential for making efficient thin-film solar cells.

Recent progress in material study and photovoltaic device of Sb2Se3

Recently, antimony selenide (Sb2Se3) has been proposed as an alternative earth-abundant absorber material for thin film solar cells. Sb2Se3 is a simple V2-VI3 binary compound with an orthorhombic crystal structure and a space group of Pnma 62. It is a staggered layered compound consisting of parallel 1D (Sb4Se6)n ribbons held together by weak van der Waals forces. Sb2Se3 has a direct band gap of approximately 1.15 eV with a large absorption coefficient (>105 cm-1, at short wavelength) and a low grain growth temperature (～300^{o}C), facilitating the fabrication of low-cost thin film solar cells. Moreover, it is a simple binary compound in single phase with a fixed composition, which provides a much simpler growth chemistry than the multicomponent Cu2ZnSn(S,Se)4. In addition, it is stable upon exposure to the ambient air, thus having a better prospect for long-term stability than the organic-inorganic halide perovskite solar cells. Theoretical analysis indicates that the efficiency limit is >30% for single junction Sb2Se3 solar cells. Various approaches, including vacuum evaporation, electrodeposition, spray pyrolysis, and chemical bath deposition (CBD), have been explored to produce Sb2Se3 thin films; however, it is only in these years that Sb2Se3 solar cells have been reported by our group as well as by others. Seok's group presented the deposition of Sb2Se3 on mesoporous TiO2 films by thermal decomposition of Sb2Se3 single-source precursors, and fabricated Sb2Se3-sensitized inorganic-organic heterojunction solar cells with a remarkable efficiency of 3.21%. Tena-Zaera's group fabricated the FTO/TiO2/Sb2Se3/CuSCN/Au heterojunction device and achieved 2.1% device efficiency; their Sb2Se3 was obtained by an electrodeposition route and CuSCN served as a hole conducting layer. Different from the above Sb2Se3-sensitized solar cells reported by other groups, our group is the first in the world working on Sb2Se3 thin film solar cells so far as wu know. We have fabricated a hydrazine solution-processed TiO2/Sb2Se3 heterojunction solar cell, achieving 2.26% device efficiency (Voc = 0.52 V, Jsc = 10.3 mA/cm2 and m FF = 42.3%). In addition to the solution processing method, thermal-evaporated substrate and superstrate CdS/Sb2Se3 thin film solar cells with 2.1% and 1.9% efficiencies respectively were also demonstrated by our group. Recently, we have further improved the superstrate device performance to 3.7% (Voc=0.335 V, Jsc=24.4 mA/cm2, and m FF=46.8%$) by using a post selenization step. Selenization can compensate the Se loss during thermal evaporation, attenuate selenium vacancy-related recombination loss and hence improve the device performance. In summary, this paper summarizes the recent research progress in Sb2Se3-related researches, including material properties of Sb2Se3, synthesis of Sb2Se3 nanomaterials and thin films, theoretical studies on electrical properties, device configuration and efficiency improvement of Sb2Se3 sensitized and thin film solar cells. This review also presents a perspective on future development of Sb2Se3 solar cells.