Nano-Scale Smoothing of Double Layer Porous Si Substrates for Detaching
and Fabricating Low Cost, High Efficiency Monocrystalline Thin Film Si Solar
Cell By Zone Scanning Annealing
ABSTRACTIn order to make high efficiency and low cost solar cell modules, the concept of third generation of photovoltaic modules have been provided. The first generation solar cell: Crystal Si solar cell including single crystal and poly-crystal Si solar cell；The second generation solar cell：Thin film solar cell including Si base thin film, CIGS, CdTe and III-V thin films; The third generation solar cell is the future high efficiency and low cost solar cell modules, such as low cost quantum dots solar cell, Si base thin film tandem and triple cell modules, III-V solar cell on Si, HIT solar cell and nanotechnology with no vacuum technique such as printable technologies and etc. This paper reviewed the advantages and disadvantages of each generation of the solar cell modules and technologies and discussed the research and development of the third generation of photovoltaic modules including the detail technology developments.
In this study, commercially available white paint is used as a pigmented dielectric reflector (PDR) in the fabrication of a low-cost back electrode stack with an Al-doped ZnO (AZO) layer for thin-film silicon solar cell applications. An initial AZO film was deposited by the radio-frequency magnetron sputtering method. In order to obtain the highest transmittance and lowest resistivity of AZO film, process parameters such as sputtering power and substrate temperature were investigated. The optimal 100-nm-thick AZO film with low resistivity and high transmittance in the visible region are 6.4 × 10−3 Ω·cm and above 80%, respectively. Using glue-like white paint doped withTiO2 nanoparticles as the PDR enhances the external quantum efficiency (EQE) of a microcrystalline silicon absorptive layer owing to the doped white particles improving Fabry–Pérot interference (FPI), which raises reflectance and scattering ability. To realize the cost down requirement, decreasing the noble metal film thickness such as a 30-nm-thick silver reflector film, and a small doping particle diameter (D50 = 135 nm) and a high solid content (20%) lead to FPI improvement and a great EQE, which is attributed to improved scattering and reflectivity because of optimum diameter (Dopt) and thicker PDR film. The results indicate that white paint can be used as a reflector coating in low-cost back-electrode structures in high-performance electronics.
AbstractThin, polycrystalline silicon solar cells have the potential for the realization of a 15%, lowcost photovoltaic product. As a photovoltaic material, polycrystalline material is abundant, benign, and electrically stable. The thin-film polycrystalline silicon solar cell design achieves high efficiency by incorporating techniques to enhance optical absorption, ensure electrical confinement, and minimize bulk recombination currents. AstroPower's approach to a thin-film polycrystalline silicon solar cell technology is based on the Silicon-Film™ process, a continuous sheet manufacturing process for the growth of thin films of polycrystalline silicon on low-cost substrates. A new barrier layer and substrate have been developed for advanced solar cell designs. External gettering with phosphorus has been employed to effect significant improvements leading to effective minority carrier diffusion lengths greater than 250 micrometers in the active silicon layer. Light trapping has been observed in 60-micrometer thick films of silicon grown on the new barrier-coated substrate. An efficiency of 12.2% in a 0.659 cm2 solar cell has been achieved with the advanced structure.
In this report, we present a process for the fabrication and tapering of a silicon (Si) nanopillar (NP) array on a large Si surface area wafer (2-inch diameter) to provide enhanced light harvesting for Si solar cell application. From our N,N-dimethyl-formamide (DMF) solvent-controlled spin-coating method, silica nanosphere (SNS in 310 nm diameter) coating on the Si surface was demonstrated successfully with improved monolayer coverage (>95%) and uniformity. After combining this method with a reactive ion etching (RIE) technique, a high-density Si NP array was produced, and we revealed that controlled tapering of Si NPs could be achieved after introducing a two-step RIE process using (1) CHF3/Ar gases for SNS selective etching over Si and (2) Cl2 gas for Si vertical etching. From our experimental and computational study, we show that an effectively tapered Si NP (i.e., an Si nanotip (NT)) structure could offer a highly effective omnidirectional and broadband antireflection effect for high-efficiency Si solar cell application.
Polycrystalline thin films of II-VI semiconductors on foreign polycrystalline (or amorphous) substrates have many applications in optoelectronic devices. In contrast to the extensive studies of the heteroepitaxial growth of compound semiconductors on single-crystal substrates, the nucleation and growth of thin films of II-VI compounds on foreign substrates have received little attention, and the properties of these films are often controlled empirically to optimize device performance. A better understanding of the nucleation, growth, and microstructure will facilitate a better control of the structural and electrical properties of polycrystalline semiconductor films, thereby improving the device characteristics. Cadmium telluride (CdTe) has long been recognized as a promising thin-film photovoltaic material. Under NREL's sponsorship, the University of South Florida has recently developed a record high efficiency (14.6% under global AM1.5 conditions) thin-film CdS/CdTe heterojunction solar cell for potential low-cost photovoltaic applications. The solar cell has the structure:glass (substrate)/SnO2:F/CdS/CdTe/HgTe (contact)The CdS films were grown from an aqueous solution, while the CdTe films were deposited by the closespaced sublimation method.
Solar energy is abundant, clean, and renewable, making it an ideal energy source. Solar cells are a good option to harvest this energy. However, it is difficult to balance the cost and efficiency of traditional thin-film solar cells, whereas nanowires (NW) are far superior in making high-efficiency low-cost solar cells. Therefore, the NW solar cell has attracted great attention in recent years and is developing rapidly. Here, we review the great advantages, recent breakthroughs, novel designs, and remaining challenges of NW solar cells. Special attention is given to (but not limited to) the popular semiconductor NWs for solar cells, in particular, Si, GaAs(P), and InP.
ABSTRACTFor the industrial application of silicon thin film solar cells, the current focus is on how to realize high-efficiency low-cost production process and minimize light-induced degradation effect, thus effectively reducing the balance-of-system (BOS) costs of system integration. In this paper, a brief introduction based on our development and application in this area is presented, highlighting in the achievement of some layers in a-Si:H/μc-Si:H tandem solar cell by optimizing the property of single layers, such as amorphous intrinsic layer, intermediate reflective layer and microcrystalline intrinsic layer. After transferring the process achievement to the industrial production line, we obtained the low-cost thin-film silicon solar cells with high photovoltaic conversion efficiency of 10.2%.
Omnidirectional and Broadband Antireflection Effect with Tapered Silicon Nanostructures Fabricated with Low-Cost and Large-Area Capable Nanosphere Lithography