Organic/silicon nanowires (SiNWs) hybrid solar cells have recently been recognized as one of potentially low-cost candidates for photovoltaic application. Here, we have controllably prepared a series ...of uniform silicon nanowires (SiNWs) with various diameters on silicon substrate by metal-assisted chemical etching followed by thermal oxidization, and then fabricated the organic/SiNWs hybrid solar cells with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (
PSS). It is found that the reflective index of SiNWs layer for sunlight depends on the filling ratio of SiNWs. Compared to the SiNWs with the lowest reflectivity (LR-SiNWs), the solar cell based on the SiNWs with low filling ratio (LF-SiNWs) has a higher open-circuit voltage and fill factor. The capacitance-voltage measurements have clarified that the built-in potential barrier at the LF-SiNWs/
PSS interface is much larger than that at the LR-SiNWs/PEDOT one, which yields a strong inversion layer generating near the silicon surface. The formation of inversion layer can effectively suppress the carrier recombination, reducing the leakage current of solar cell, and meanwhile transfer the LF-SiNWs/
PSS device into a p-n junction. As a result, a highest efficiency of 13.11% is achieved for the LF-SiNWs/
PSS solar cell. These results pave a way to the fabrication of high efficiency organic/SiNWs hybrid solar cells.
In this study, we prepare Erbium compound nanocrystals and Si nanocrystal (Si NC) co-embedded silica film by the sol-gel method. Dual phases of Si and Er chloride silicate (ECS) nanocrystals were ...coprecipitated within amorphous silica. Effective sensitized emission of Er chloride silicate nanocrystals was realized via interparticle energy transfer between silicon nanocrystal and Er chloride silicate nanocrystals. The influence of density and the distribution of sensitizers and Er compounds on interparticle energy transfer efficiency was discussed. The interparticle energy transfer between the semiconductor and erbium compound nanocrystals offers some important insights into the realization of efficient light emission for silicon-based integrated photonics.
Silicon has dominated the photovoltaic material market for a few decades. In contrast to perfectly crystallized Czochralski (CZ) silicon, casting multi‐crystalline silicon attracts much more ...attention due to its low cost and high throughput, which meets the increasing demands of the rapidly developing photovoltaic industry. However, the unavoidable appearance of crystallographic defects seriously limits the performance improvement of solar cells. In this Review, a general overview of the recent efforts in high‐quality casting silicon crystal techniques is provided, including the dendritic cast method, high‐performance multi‐crystalline silicon, and cast‐mono silicon. Then, special attention is focused on the seed‐assisted growth of cast‐mono silicon, which shares some of the most favorable features of high solar cell efficiency offered by well‐established CZ silicon and cost‐effectiveness of cast multi‐crystalline silicon. Nevertheless, this innovative growth technique facing a few challenges once impeded its mass scale production. The main issues concerning nucleation and growth control, extended defects as well as impurity contamination are addressed, which pave the way for this high‐potential technology in applications for high‐efficiency and low‐cost solar cells.
A general overview of recent efforts in high‐quality casting silicon techniques is given, and special attention is focused on the seed‐assisted growth of cast‐mono silicon. The core issues concerning growth control, defects and impurities are investigated intensively. The origins of formation of extended defects and strategies for improving the quality of cast‐mono silicon are well addressed.
Abstract
We present a self-powered, high-performance graphene-enhanced ultraviolet silicon Schottky photodetector. Different from traditional transparent electrodes, such as indium tin oxides or ...ultra-thin metals, the unique ultraviolet absorption property of graphene leads to long carrier life time of hot electrons that can contribute to the photocurrent or potential carrier-multiplication. Our proposed structure boosts the internal quantum efficiency over 100%, approaching the upper-limit of silicon-based ultraviolet photodetector. In the near-ultraviolet and mid-ultraviolet spectral region, the proposed ultraviolet photodetector exhibits high performance at zero-biasing (self-powered) mode, including high photo-responsivity (0.2 A W
−1
), fast time response (5 ns), high specific detectivity (1.6 × 10
13
Jones), and internal quantum efficiency greater than 100%. Further, the photo-responsivity is larger than 0.14 A W
−1
in wavelength range from 200 to 400 nm, comparable to that of state-of-the-art Si, GaN, SiC Schottky photodetectors. The photodetectors exhibit stable operations in the ambient condition even 2 years after fabrication, showing great potential in practical applications, such as wearable devices, communication, and “dissipation-less” remote sensor networks.
4H silicon carbide (4H‐SiC) holds great promise for high‐power and high‐frequency electronics, in which high‐quality 4H‐SiC wafers with both global and local planarization are cornerstones. ...Chemical–mechanical polishing (CMP) is the key processing technology in the planarization of 4H‐SiC wafers. Enhancing the performance of CMP is critical to improving the surface quality and reducing the processing cost of 4H‐SiC wafers. In this review, the superior properties of 4H‐SiC and the processing of 4H‐SiC wafers are introduced. The development of CMP with chemical, mechanical, and chemical–mechanical synergistic approaches to improve the performance of CMP is systematically reviewed. The basic principle and processing system of each improvement approach are presented. By comparing the material removal rate of CMP and the surface roughness of CMP‐treated 4H‐SiC wafers, the prospect on the chemical, mechanical, and chemical–mechanical synergistic improvement approaches is finally provided.
Recent progress on the CMP of 4H‐SiC wafers are discussed after a brief overview of the basic properties of 4H‐SiC. Chemical, mechanical, and chemical–mechanical synergistic approaches for the efficiency improvement of CMP are highlighted. By discussing the advantages and disadvantages of the efficiency‐improvement approaches, the challenges of using these approaches in industry are analyzed. Finally, prospects on the development of the CMP of 4H‐SiC wafers are presented.
Abstract
The pressure-dependent lattice dynamics of 4H-SiC is investigated using diamond anvil cell, and compared with those of 3C- and 6H-SiC. It is found that both the zone-center longitudinal ...optical (LO) and transverse optical (TO) modes shift to higher frequencies with the increase of the applied pressures. This indicates that polymorph transitions are unlikely to happen under the (quasi-)hydrostatic pressure. The LO–TO splitting is described well by the cubic function with respect to the applied pressure. A decrease in the LO–TO splitting is observed above 33 GPa. The change of transverse effective charge and thus the ionic character of 4H-SiC exhibits a cubic dependence on the pressure due to the nonequivalent lattice dynamics parallel and perpendicular to the
c
-axis of 4H-SiC. Compared to what happens in 6H-SiC, the high pressure exerts higher effect on the ionic character of 4H-SiC because less nonequivalent bilayers are evolved. At last, the mode-Grüneisen parameters of the LO and TO modes at the Γ point are determined. Given the hexagonal lattice of 4H-SiC, the LO mode are softer than the TO mode.
Dislocation clusters and sub-grain boundaries (Sub-GBs) induced by the misorientation between adjacent seeds are destructive to the quasi-single crystal (QSC) Si ingot quality and the solar cell ...efficiency. Here, we have designed an artificial Σ13 GB between two adjacent -oriented seeds at the crucible bottom. It is found that the generation of dislocation clusters and sub-GBs from the seed junctions is significantly suppressed owing to the low energy barrier potential of the Σ13 GB. Although some twins could generate from the vertical Σ13 GB, they will not give a bad influence on the ingot quality. The efficiency of solar cells is absolutely high in industrial circles, with an average value of 20.1%. These results pave a new way to the fabrication of high quality QSC-Si ingots for photovoltaic application.
Using an improved seed-mediated growth method, complete silver shells were coated onto silica spheres.
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► SiO
2@Ag particles with complete and smooth silver shells were prepared using ...an improved seed-mediated method. ► Rapid reaction in growth process of silver shells was considered to be very important. ► PVP was used to control the isotropic growth of silver nuclei and to avoid the aggregation of core–shell particles.
We synthesized SiO
2@Ag core–shell particles with uniform and complete silver shells with an improved seed-mediated growth method. Silver nuclei produced on silica spheres with an electroless plating method served as nucleation sites for the growth of outer silver shells. By adjusting the Ag/SiO
2 ratio, the thickness of silver shells was tuned, and the extinction peaks of SiO
2@Ag particles shifted from visible to near-infrared (NIR) region. Comparing with previously reported methods, two important strategies were employed in the growth step of silver shells. First, polyvinylpyrrolidone (PVP) was added to control the isotropic growth of silver nuclei and improve the stability of core–shell particles. Second, the growth step of the outer silver shells was completed in a few seconds by increasing the reaction temperature and pH value. Furthermore, the SiO
2@Ag core–shell particles were self-assembled into a monolayer, which served as a good SERS substrate.
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▶ A low-cost solar grade silicon purification process is proposed. ▶ This process makes purification of silicon easily achieved at a lower temperature. ▶ The impurity content of ...purified silicon is very low. ▶ This process has better yield than the conventional process.
Silicon solar cell is one of the cleanest and most potential renewable resources. However, the high cost of raw material is impeding the development of silicon solar cell. In this paper, we have investigated a purification process designed for low-cost solar grade silicon with Al–Si system, using a powder metallurgy technique. It is found that by modulating the external pressure and/or protection ambient, the alloying of Al–Si powder mixture is easily accomplished at a relatively lower temperature. The mechanism of Si products purified from the Al–Si melt has been discussed based on their morphological characterizations. The impurity contents of the purified Si products can be controlled at a very low level (∼3
ppmw). Meanwhile, the yield of the purified Si products using the powder metallurgy technique is clarified to be higher than that of the conventional Al–Si purification technique without external pressure or protecting ambient. The process is quite potential of providing low-cost solar grade silicon feedstock for photovoltaic industry.
Perovskite photovoltaics, typically based on a solution-processed perovskite layer with a film thickness of a few hundred nanometres, have emerged as a leading thin-film photovoltaic technology. ...Nevertheless, many critical issues pose challenges to its commercialization progress, including industrial compatibility, stability, scalability and reliability. A thicker perovskite film on a scale of micrometres could mitigate these issues. However, the efficiencies of thick-film perovskite cells lag behind those with nanometre film thickness. With the mechanism remaining elusive, the community has long been under the impression that the limiting factor lies in the short carrier lifetime as a result of defects. Here, by constructing a perovskite system with extraordinarily long carrier lifetime, we rule out the restrictions of carrier lifetime on the device performance. Through this, we unveil the critical role of the ignored lattice strain in thick films. Our results provide insights into the factors limiting the performance of thick-film perovskite devices.
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