Nanoscale Bi-based photocatalysts are promising candidates for visible-light-driven photocatalytic environmental remediation and energy conversion. However, the performance of bulk bismuthal semiconductors is unsatisfactory. Increasing efforts have been focused on enhancing the performance of this photocatalyst family. Many studies have reported on component adjustment, morphology control, heterojunction construction, and surface modification. Herein, recent topics in these fields, including doping, changing stoichiometry, solid solutions, ultrathin nanosheets, hierarchical and hollow architectures, conventional heterojunctions, direct Z-scheme junctions, and surface modification of conductive materials and semiconductors, are reviewed. The progress in the enhancement mechanism involving light absorption, band structure tailoring, and separation and utilization of excited carriers, is also introduced. The challenges and tendencies in the studies of nanoscale Bi-based photocatalysts are discussed and summarized.

Review on nanoscale Bi-based photocatalysts

A review on perovskite solar cells: Evolution of architecture, fabrication techniques, commercialization issues and status

With the rapid increase of efficiency up to 22.1% during the past few years, hybrid organic-inorganic metal halide perovskite solar cells (PSCs) have become a research “hot spot” for many solar cell researchers. The perovskite materials show various advantages such as long carrier diffusion lengths, widely-tunable band gap with great light absorption potential. The low-cost fabrication techniques together with the high efficiency makes PSCs comparable with Si-based solar cells. But the drawbacks such as device instability, J-V hysteresis and lead toxicity reduce the further improvement and the future commercialization of PSCs. This review begins with the discussion of crystal and electronic structures of perovskite based on recent research findings. An evolution of PSCs is also analyzed with a greater detail of each component, device structures, major device fabrication methods and the performance of PSCs acquired by each method. The following part of this review is the discussion of major barriers on the pathway for the commercialization of PSCs. The effects of crystal structure, fabrication temperature, moisture, oxygen and UV towards the stability of PSCs are discussed. The stability of other components in the PSCs are also discussed. The lead toxicity and updated research progress on lead replacement are reviewed to understand the sustainability issues of PSCs. The origin of J-V hysteresis is also briefly discussed. Finally, this review provides a roadmap on the current needs and future research directions to address the main issues of PSCs.

Perovskites-Based Solar Cells: A Review of Recent Progress, Materials and Processing Methods

The perovskite structure is shown to be the single most versatile ceramic host. Inorganic perovskite type oxides are attractive compounds for varied applications due to its large number of compounds, they exhibit both physical and biochemical characteristics and their Nano-formulation have been utilized as catalysts in many reaction due to their sensitivity, unique long-term stability and anti-interference ability. Some perovskites materials are very hopeful applicants for the improvement of effective anodic catalysts performance. Depending Perovskite-phase metal oxides distinct variety of properties they became useful for various applications they are newly used in electrochemical sensing of alcohols, glucose, hydrogen peroxide, gases, and neurotransmitters. Perovskite organometallic halide showed efficient essential properties for photovoltaic solar cells. This review presents a full coverage of the structure, progress of perovskites and their related applications. Stress is focused particularly to different methods of perovskites properties and there related application.

Perovskite synthesis, properties and their related biochemical and industrial application

Already, several technologies of polycrystalline thin‐film photovoltaic materials have achieved certified record small‐cell power conversion efficiencies exceeding 22%. They are CdTe, Cu(In,Ga)(S,Se)2 (CIGS), and metal halide perovskite (PSC), each named after the light-absorbing semiconductor material. Thin-film solar cells and modules require very little active material due to their very high absorption coefficient. Efficient production methods with low materials waste, moderate temperatures, attractive cost structures, and favorable energy payback times will play a strong role in market development as thin-film technologies reach full maturity, including mass production and the standardization of production machineries. In fact, the first two technologies have already been developed up to the industrial scale with a market share of several GW. In this review article, we outline similarities and differences between these high‐efficiency thin‐film technologies from both the materials and the industrial point of view. We address the materials characteristics and device concepts for each technology, including a description of recent developments that have led to very high efficiency achievements. We provide an overview of the CIGS industry players and their current status. The newcomer PSC has demonstrated its potential in the laboratory, and initial efforts in industrial production are underway. A large number of laboratories are experimenting through a wide range of options in order to optimize not only the efficiency but also stability, environmental aspects, and manufacturability of PSC. Its high efficiency and its high bandgap make PSC particularly attractive for tandem applications. An overview of all these topics is included here along with a list of materials configurations.

Thin‐film solar cells exceeding 22% solar cell efficiency: An overview on CdTe-, Cu(In,Ga)Se2-, and perovskite-based materials

A novel all-solid-state, hybrid solar cell based on organic-inorganic metal halide perovskite (CH3NH3PbX3) materials has attracted great attention from the researchers all over the world and is considered to be one of the top 10 scientific breakthroughs in 2013. The perovskite materials can be used not only as light-absorbing layer, but also as an electron/hole transport layer due to the advantages of its high extinction coefficient, high charge mobility, long carrier lifetime, and long carrier diffusion distance. The photoelectric power conversion efficiency of the perovskite solar cells has increased from 3.8% in 2009 to 22.1% in 2016, making perovskite solar cells the best potential candidate for the new generation of solar cells to replace traditional silicon solar cells in the future. In this paper, we introduce the development and mechanism of perovskite solar cells, describe the specific function of each layer, and focus on the improvement in the function of such layers and its influence on the cell performance. Next, the synthesis methods of the perovskite light-absorbing layer and the performance characteristics are discussed. Finally, the challenges and prospects for the development of perovskite solar cells are also briefly presented.

/pdf/perovskite-based-solar-cells-materials-methods-and-future-ant7b9u6op.pdf

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

A facile two-step synthesis route combining electrospinning and hydrothermal techniques has been performed to obtain Bi2Ti2O7/TiO2 heterostructured submicron fibers. Bi2Ti2O7 nanosheets were grown on the surface of TiO2 submicron fibers. The density of the nanosheets increased with higher precursor concentration of the Bi/Ti reaction raw materials. UV-visible (UV-vis) diffuse reflectance spectroscopy indicated that the absorption spectrum of the Bi2Ti2O7/TiO2 composite extended into the visible-light region. Photocatalytic tests showed that the Bi2Ti2O7/TiO2 heterostructures possess a much higher degradation rate of rhodamine B than the unmodified TiO2 submicron fibers under visible light. The enhanced photocatalytic activity can be attributed to the synergistic effect between improved visible-light absorption and the internal electric field created by the heterojunctions. The effective separation of photogenerated carriers driven by the photoinduced potential was demonstrated by the photoelectrochemical analysis.

https://link.springer.com/content/pdf/10.1186%2Fs11671-016-1408-7.pdf

In Situ Fabrication of Bi2Ti2O7/TiO2 Heterostructure Submicron Fibers for Enhanced Photocatalytic Activity

In this paper, Bi2S3 microflowers have been successfully synthesized via a facile one-pot hydrothermal method and characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy. Then the Bi2S3 microflowers were deposited on patterned ITO glass substrates by dip-coating to fabricate photodetectors. The photoresponse properties using Bi2S3 microflowers as a representative system show a significantly enhanced conductivity and the current–voltage characteristic exhibit ca. 1.7 orders of magnitude larger than the dark current. The response and decay times are estimated to be ~227 and 880 ms, respectively, indicating that flower-like Bi2S3 may be an excellent candidate for high-speed and high-sensitivity photoelectrical switches and light-sensitive devices.

Bi2S3 microflowers assembled from one-dimensional nanorods with a high photoresponse

This paper reported a simple and effective method for fabricating and patterning highly ordered ZnO nanorod arrays on H2-decomposed GaN epilayer via hydrothermal route. The edge of pattern, which has been decomposed by H2 flow, provides appropriate nucleation sites for the selective-growth of aligned ZnO nanorods. The density of ZnO nanorod arrays assembled the hexagonal pattern can be tuned by varying the solution concentrations, growth time and reaction temperatures. The results have demonstrated that the ZnO nanorods are highly uniform in diameter and height with perfect alignment and are epitaxially grown along [0001] direction. This work provides a novel and accessible route to prepare oriented and aligned ZnO nanorod arrays pattern. And the aligned ZnO nanorods form an ideal hexagonal pattern that might be used in many potential applications of ZnO nanomaterials.

Xiaolong Zhu

Papers

Perovskite-Based Solar Cells: Materials, Methods, and Future Perspectives

In Situ Fabrication of Bi2Ti2O7/TiO2 Heterostructure Submicron Fibers for Enhanced Photocatalytic Activity

Bi2S3 microflowers assembled from one-dimensional nanorods with a high photoresponse

Selective growth and characterization of ZnO nanorods assembled a hexagonal pattern on H2-decomposed GaN epilayer

Preparation of BiFeO3-overcoated TiO2 nanorod arrays for the enhanced visible-light activity