Quasi-Vertically-Orientated Antimony Sulfide Inorganic Thin-Film Solar Cells Achieved by Vapor Transport Deposition

Structural Decoration of Porphyrin/Phthalocyanine Photovoltaic Materials

Porphyrin/phthalocyanine compounds with fascinating molecular structures have attracted widespread attention in the field of solar cells in recent years. In this review, we focus on the pivotal role of porphyrin and phthalocyanine compounds in enhancing the efficiency of solar cells. The review seamlessly integrates the intricate molecular structures of porphyrins and phthalocyanines with their proficiency in absorbing visible light and facilitating electron transfer, key processes in converting sunlight into electricity. By delving into the nuances of intramolecular regulation, aggregated states, and surface/interface structure manipulation, it elucidates how various levels of molecular modifications enhance solar cell efficiency through improved charge transfer, stability, and overall performance. This comprehensive exploration provides a detailed understanding of the complex relationship between molecular design and solar cell performance, discussing current advancements and potential future applications of these molecules in solar energy technology.

Precursor Engineering of Solution-Processed Sb2 S3 Solar Cells

Antimony-based chalcogenides have emerged as promising candidates for next-generation thin film photovoltaics. Particularly, binary Sb2 S3 thin films have exhibited great potential for optoelectronic applications, due to the facile and low-cost fabrication, simple composition, decent charge transport and superior stability. However, most of the reported efficient Sb2 S3 solar cells are realized based on chemical bath deposition and hydrothermal methods, which require large amount of solution and are normally very time-consuming. In this work, Ag ions are introduced within the Sb2 S3 sol-gel precursors, and effectively modulated the crystallization and charge transport properties of Sb2 S3 . The crystallinity of the Sb2 S3 crystal grains are enhanced and the charge carrier mobility is increased, which resulted improved charge collection efficiency and reduced charge recombination losses, reflected by the greatly improved fill factor and open-circuit voltage of the Ag incorporated Sb2 S3 solar cells. The champion devices reached a record high power conversion efficiency of 7.73% (with antireflection coating), which is comparable with the best photovoltaic performance of Sb2 S3 solar cells achieved based on chemical bath deposition and hydrothermal techniques, and pave the great avenue for next-generation solution-processed photovoltaics.

Critical Review on Crystal Orientation Engineering of Antimony Chalcogenide Thin Film for Solar Cell Applications

The emerging antimony chalcogenide (Sb2 (Sx Se1-x )3 , 0 ≤ x ≤ 1) semiconductors are featured as quasi-1D structures comprising (Sb4 S(e)6 )n ribbons, this structural characteristic generates facet-dependent properties such as directional charge transfer and trap states. In terms of carrier transport, proper control over the crystal nucleation and growth conditions can promote preferentially oriented growth of favorable crystal planes, thus enabling efficient electron transport along (Sb4 S(e)6 )n ribbons. Furthermore, an in-depth understanding of the origin and impact of the crystal orientation of Sb2 (Sx Se1-x )3 films on the performance of corresponding photovoltaic devices is expected to lead to a breakthrough in power conversion efficiency. In fact, there are many studies on the orientation control of Sb2 (Sx Se1-x )3 colloidal nanomaterials. However, the synthesis of Sb2 (Sx Se1-x )3 thin films with controlled facets has recently been a focus in optoelectronic device applications. This work summarizes methodologies that are applied in the fabrication of preferentially oriented Sb2 (Sx Se1-x )3 films, including treatment strategies developed for crystal orientation engineering in each process. The mechanisms in the orientation control are thoroughly analyzed. An outlook on perspectives for the future development of Sb2 (Sx Se1-x )3 solar cells based on recent research and issues on orientation control is finally provided.

A Novel Multi-Sulfur Source Collaborative Chemical Bath Deposition Technology Enables 8%-Efficiency Sb2 S3 Planar Solar Cells

Sb₂ S₃ as a light-harvesting material has attracted great attention for applications in both single-junction and tandem solar cells. Such solar cell has been faced with current challenge of low power conversion efficiency (PCE), which has stagnated for 8 years. It has been recognized that the synthesis of high-quality absorber film plays a critical role in efficiency improvement. Here, using fresh precursor materials for antimony (antimony potassium tartrate) and combined sulfur (sodium thiosulfate and thioacetamide), a unique chemical bath deposition procedure is created. Due to the complexation of sodium thiosulfate and the advantageous hydrolysis cooperation between these two sulfur sources, the heterogeneous nucleation and the S^2- releasing processes are boosted. As a result, there are noticeable improvements in the deposition rate, film morphology, crystallinity, and preferred orientations. Additionally, the improved film quality efficiently lowers charge trapping capacity, suppresses carrier recombination, and prolongs carrier lifetimes, leading to significantly improved photoelectric properties. Ultimately, the PCE exceeds 8% for the first time since 2014, representing the highest efficiency in all kinds of Sb₂ S₃ solar cells to date. This study is expected to shed new light on the fabrication of high-quality Sb₂ S₃ film and further efficiency improvement in Sb₂ S₃ solar cells.

Effects of working pressure on the material and defect properties of Sb2S3 thin-film solar cells achieved by the VTD method

Antimony sulfide (Sb₂S₃), an emerging material for photovoltaic devices, has drawn growing research interest due to its inexpensive and high-throughput device production. In this study, the material and defect properties of Sb₂S₃ thin films prepared by the vapor transport deposition (VTD) method at different working pressures were studied. Solar cells based on a structure of glass/ITO/CdS/Sb₂S₃/Au were fabricated. The working pressure showed a significant effect on the device's performance. The current density versus voltage measurement and scanning electron microscopy analysis outcome were utilized to investigate the photovoltaic and microstructural properties in the samples. The compositional analysis by energy dispersive X-ray spectroscopy measurement confirmed the Sb/S ratio as 2:2.8 for the thin films. The identification and characterization of the defects present in Sb₂S₃ thin films were performed via admittance measurements. Compared to the defect density, the defect energy level was found to inherit a more important role in the device's performance. The best solar cell performance with better crystal quality, lower defect density, and longer capture lifetime was achieved under the substrate working pressure of 2 Pa. The highest efficiency was found to be 0.86% with V_oc=0.55V, J_sc=5.07mA/cm².

Molecular precursor-mediated facile synthesis of photo-responsive stibnite Sb2S3 nanorods and tetrahedrite Cu12Sb4S13 nanocrystals

Stibnite Sb₂S₃ and tetrahedrite Cu₁₂Sb₄S₁₃ nanostructures being economical, environmentally benign and having a high absorption coefficient are highly promising materials for energy conversion applications. However, producing these materials especially tetrahedrite in the phase pure form is a challenging task. In this report we present a structurally characterized single source molecular precursor [Sb(4,6-Me₂pymS)₃] for the facile synthesis of binary Sb₂S₃ as well as ternary Cu₁₂Sb₄S₁₃ in oleylamine (OAm) at a relatively lower temperature. The as-prepared Sb₂S₃ and Cu₁₂Sb₄S₁₃ nanostructures were thoroughly checked for their phase purity, elemental composition and morphology by powder X-ray diffraction (pXRD), electron dispersive spectroscopy (EDS) and electron microscopy techniques. pXRD and EDS studies confirm the formation of phase pure, crystalline orthorhombic Sb₂S₃ and cubic Cu₁₂Sb₄S₁₃. The SEM, TEM and HRTEM images depict the formation of well-defined nanorods and nearly spherical nanocrystals for Sb₂S₃ and Cu₁₂Sb₄S₁₃, respectively. The Sb₂S₃ nanorods and Cu₁₂Sb₄S₁₃ nanocrystals exhibit an optical bandgap of ∼1.88 and 2.07 eV, respectively, which are slightly blue-shifted relative to their bulk bandgap, indicating the quantum confinement effect. Finally, efficient photoresponsivity and good photo-stability were achieved in the as-prepared Sb₂S₃ and Cu₁₂Sb₄S₁₃ nanostructure-based prototype photo-electrochemical cell, which make them promising candidates for alternative low-cost photon absorber materials.

Lone pair driven anisotropy in antimony chalcogenide semiconductors

Antimony sulfide (Sb2S3) and selenide (Sb2Se3) have emerged as promising earth-abundant alternatives among thin-film photovoltaic compounds. A distinguishing feature of these materials is their anisotropic crystal structures, which are composed of quasi-one-dimensional (1D) [Sb4X6]n ribbons. The interaction between ribbons has been reported to be van der Waals (vdW) in nature and Sb2X3 are thus commonly classified in the literature as 1D semiconductors. However, based on first-principles calculations, here we show that inter-ribbon interactions are present in Sb2X3 beyond the vdW regime. The origin of the anisotropic structures is related to the stereochemical activity of the Sb 5s lone pair according to electronic structure analysis. The impacts of structural anisotropy on the electronic, dielectric and optical properties relevant to solar cells are further examined, including the presence of higher dimensional Fermi surfaces for charge carrier transport. Our study provides guidelines for optimising the performance of Sb2X3-based photovoltaics via device structuring based on the underlying crystal anisotropy.

Zn(O,S) Buffer Layer for in Situ Hydrothermal Sb2S3 Planar Solar Cells

Hydrothermal deposition is emerging as a highly potential route for antimony-based solar cells, in which the Sb₂(S,Se)₃ is typically in situ grown on a common toxic CdS buffer layer. The narrow band gap of CdS causes a considerable absorption in the short-wavelength region and then lowers the current density of the device. Herein, TiO₂ is first evaluated as an alternative Cd-free buffer layer for hydrothermally derived Sb₂S₃ solar cells. But it suffers from a severely inhomogeneous Sb₂S₃ coverage, which is effectively eliminated by inserting a Zn(O,S) layer. The surface atom of sulfur in Zn(O,S) uniquely provides a chemical bridge to enable the quasi-epitaxial deposition of Sb₂S₃ thin film, confirming by both morphology and binding energy analysis using DFT. Then the results of the first-principles calculations also show that Zn(O,S)/Sb₂S₃ has a more stable structure than TiO₂/Sb₂S₃. The resultant perfect Zn(O,S)/Sb₂S₃ junction, with a suitable band alignment and excellent interface contact, delivers a remarkably enhanced J_SC and V_OC for Sb₂S₃ solar cells. The device efficiency with the TiO₂/Zn(O,S) buffer layer boosts from 0.54% to 3.70% compared with the counterpart of TiO₂, which has a champion efficiency of Cd-free Sb₂S₃ solar cells with a structure of ITO/TiO₂/Zn(O,S)/Sb₂S₃/Carbon/Ag by in situ hydrothermal deposition. This work provides a guideline for the hydrothermal deposition of antimony-based films upon a nontoxic buffer layer.

Electrical response of organic molecule supported preformed and in situ formed antimony sulfide nanoparticles under frequency conditions

A complexation route mediated synthesis of orthorhombic antimony sulfide nanoparticles is described in this report where uniformly distributed particles within the size range of 2-12 nm are stabilized within the aniline matrix. The organic-inorganic hybrid system was investigated for dielectric capacitance and electric field-induced polarization performances under varying temperature and frequency conditions. The AC-conductivity revealed a correlated barrier hopping conduction mechanism in the hybrid system. A fatigue free polarization was achieved under the electric field of 9 kV mm^-1 for the preformed antimony sulfide system with a stable value of 0.18 μC cm^-2. The in situ dielectric capacitance and field dependent polarization measurements were also performed for the in situ synthesized antimony sulfide using the antimony-aniline complex as the precursor.