低能粒子辐照对铝膜反射镜光学性能的影响

地面模拟研究了低能质子和电子对铝膜反射镜光学性能的影响。结果表明,低能质子辐照后,在200~800nm波长范围内铝膜反射镜反射率随辐照剂量增加而下降。质子辐照能量越低射程越短,则反射镜表面膜层中质子浓度越大损伤也更为明显。电子辐照射程较深,辐照作用对铝膜反射镜光学性能影响很小。     

Optical enhancement by back reflector with ZnO:Al2O3(AZO) or NiCr diffusion barrier for amorphous silicon germanium thin film solar cells

Different composite films, including Al, Ag/NiCr/Al and Al₂O₃-doped ZnO (AZO)/Ag/NiCr (AZO)/Al, were utilized as the back reflectors for p-i-n hydrogenated amorphous silicon germanium (a-SiGe:H) thin film solar cells. The experimental results indicated that the AZO leyer between silicon layers and Ag/NiCr/Al back reflector was effect in improving solar cell performance, mainly owing to an increase in short-circuit current density (J_sc) of the solar cells. In addition, the thickness of AZO film could strongly affect the J_sc. The highest solar cell performance was achieved at the AZO thickness of about 90 nm. A nickel-chromium (NiCr) or AZO film was inserted between Ag and Al as a diffusion barrier against mutual diffusion of them, the similar performances of solar cells were achieved. So AZO/Ag/NiCr (AZO)/Al could be utilized as an advanced AZO/metal back reflector for p-i-n a-SiGe:H solar cells.     

Plasma deposition of n-SiOx nanocrystalline thin film for enhancing the performance of silicon thin film solar cells

In this paper, we firstly optimized the properties of n-SiO_x nanocrystalline thin film through tuning deposition parameters by plasma enhanced chemical vapor deposition, so that we can actively control the properties of materials obtained. Secondly, we proposed using n-SiO_x/Al as back reflector for amorphous silicon (a-Si:H) solar cells. Compared to Al single-layer as back reflector, adding an n-SiO_x layer into the back reflector could improve the solar cell performance, which not only enhances the short circuit current density by an improvement of spectral response in the wavelength range of 550-750 nm, but also improves the open circuit voltage. With an optimized n-SiO_x/Al back reflector, a-Si:H solar cells with an intrinsic layer thickness of 270 nm show 13.1% enhancement in efficiency. In addition, a-Si:H/μc-Si:H tandem solar cells with n-SiO_x as intermediate reflector were also researched. As a result, it evidently balanced the current matching between top and bottom cell.     

GZO厚度对非晶硅电池中复合背电极的影响

在非晶硅太阳能电池中加入复合背电极是提高非晶硅太阳能电池光电转换效率和稳定性的有效手段.本文利用磁控溅射技术在非晶硅薄膜太阳能电池上制备了ZnO :Ga(GZO)/Al复合背电极,研究了GZO厚度对GZO薄膜光电性质及非晶硅电池中GZO/Al复合背电极性能的影响.研究表明：随着GZO层厚度的增加,GZO薄膜的光电性质均表现出较高水平,适合制备GZO/Al复合背电极;相较于单层Al背电极的非晶硅太阳能电池,具有GZO/Al复合背电极的太阳能电池性能大幅提高.当GZO层厚度为100 nm时,太阳能电池的短路电流(I_SC)、开路电压(V_OC)和填充因子(FF)分别达到8.66 mA,1.62 V和54.7%.     

Removal of a protective coating on Al by ion etching for high reflectance in the far ultraviolet

The effect of ion etching on the reflectance of Al coatings in the far ultraviolet is investigated. Ion etching of an overlayer grown on Al was performed by applying 100-300 eV Ar(+) ions using an ion gun. Ion etching was employed to remove the oxide naturally grown on an Al film that had been in contact with atmosphere. Ion etching was also used to remove part or all of the protective MgF(2) film on Al. The reflectance at 121.6 nm, H Lyman alpha line of the overlayer-removed Al surface was monitored after protecting it with a MgF(2) layer. Ion etching on both types of coatings resulted in an excellent reflectance value at 121.6 nm, whereas a reflectance loss was observed at longer wavelengths.     

Vacuum ultraviolet coatings of Al protected with MgF(2) prepared both by ion-beam sputtering and by evaporation

Ion-beam sputtering (IBS) and evaporation are the two deposition techniques that have been used to deposit coatings of Al protected with MgF(2) with high reflectance in the vacuum ultraviolet down to 115 nm. Evaporation deposited (ED) Al protected with IBS MgF(2) resulted in a larger (smaller) reflectance below (above) 125 nm than the well-known all-evaporated coatings. A similar comparison is obtained when the Al film is deposited by IBS instead of evaporation. The lower reflectance of the coatings protected with IBS versus ED MgF(2) above 125 nm is because of larger absorption of the former. Both nonprotected IBS Al, as well as IBS Al protected with ED MgF(2), resulted in a band of reflectance loss that was peaked at 127 and 157 nm, respectively. This result was attributed to the excitation of surface plasmons due to the enhancement of surface roughness with large spatial wave vectors in the sputter deposition. This reflectance loss for IBS Al protected with MgF(2) is small at the short (lambda~120 nm) and long (lambda<350 nm) wavelengths investigated. IBS Al protected with ED MgF(2) is thus a promising coating for these two spectral regions. Coatings protected with IBS MgF(2) resulted in a reflectance as high as coatings protected with ED MgF(2) at wavelengths longer than 550 nm, whereas the former had a lower reflectance below this wavelength.     

Characterization of ZnO:Al/Au/ZnO:Al trilayers for high performance transparent conducting electrodes

Symmetric ZnO:Al/Au/ZnO:Al trilayers were sputter-deposited and characterized for transparent conducting electrodes, varying the thickness of the ZnO:Al (AZO) and Au layers. The optical transmission for normal light incidence is optimum for an AZO thickness of 50 nm, due to the suppression of reflection. In this case, the transmittance is more than 0.7 for wavelengths above 400 nm and for a Au thickness of 5 nm. At the same time, the sheet resistance is approx. 30 Ω, which can be decreased to 12 Ω with the increase of the Au thickness to 9 nm. This is achieved with a moderate loss in the optical transmission. The figure of merit for transparent conducting electrodes, as introduced by G. Haacke (J. Appl. Phys. 47 (1976) 4086) yields values from 29.4 × 10^− 3 to 6.9 × 10^− 3 Ω^− 1, depending on the Au thickness and the considered wavelength range.     

Spectrally selective reflector surfaces for heat reduction in concentrator solar cells: modeling and applications of TiO₂:Nb-based thin films

The energy conversion efficiency of a conventional pn junction solar cell decreases as the temperature increases, and this may eventually lead to failures in the photovoltaic system, especially if it uses concentrated solar radiation. In this work, we show that spectrally selective reflector (SSR) surfaces can be important for reducing the heat buildup on passively cooled solar cells. We outline a computational scheme for optimizing DC magnetron-sputtered TiO?:Nb-based SSRs tailored for silicon solar cells and find good agreement of the reflectance with an experimental realization of the optimal SSR. A figure of merit for SSRs has also been derived and applied to the experimental data.     

Reflectance measurements and optical constants in the extreme ultraviolet-vacuum ultraviolet regions for SiC with a different C/Si ratio

Reflectance versus incidence angle measurements have been performed from 5 to 152 nm on samples of SiC with a different C/Si ratio deposited with rf magnetron sputtering. The optical constants of the material at different wavelengths have been determined by using a curve-fitting technique of reflectance values versus incidence angle. Complementary measurements of the incident beam polarization, film thickness, surface roughness, and stoichiometry were performed to complete the analysis of the samples.     

High roughness Ag back reflector on a metal underlayer for thin film solar cell applications

The roughness development of Ag film was investigated for potential as a back reflector material in thin film solar cells on flexible stainless steel (STS) substrates. The influence of metal underlayers was evaluated in order to obtain a rough Ag film at a low deposition temperature (≤400 °C). By depositing Ag on a 100 nm Al underlayer to induce Ag–Al alloying, the film roughness was increased three times more than that of Ag films on bare STS at 400 °C. The Ag film deposited on an Al underlayer at 350 °C exhibited 75 nm roughness and uniformly distributed crystallites, which was effective for visible light scattering. The Ag–Al alloy phase was also controlled using the thickness ratio of Ag and Al. The present work clearly demonstrated that an Ag back reflector film with a higher roughness could be fabricated through inserting a metal underlayer at a deposition temperature much lower than the 500 °C that has been reported in earlier works.     

Exchange couplings between two Fe layers in Fe/Al/Fe/Ni-Fe/NiO sandwiches

Exchange couplings between two Fe layers have been investigated in polycrystalline Fe/Al/Fe/Ni-Fe/NiO and Fe/Al/Fe/Ni-Fe sandwiches. Linear exchange couplings between the two Fe layers were strong and ferromagnetic when the thickness of the Al spacer was between 0.7 and 2.2 nm. We observed biquadratic exchange couplings (90 degree couplings) when the thickness of the Al spacer was between 2.5 and 4.0 nm.     

Study of anodized Al substrate for electronic packaging

Al metal substrate with an anodic film separating the circuitry from the metal plate was developed by the means of anodization in this study. It was shown that an anodic film around 20–30 m thickness possessed the better properties, the resistivity was greater than 10¹⁴ cm, the dielectric constant was about 7 and the breakdown voltage exceeded 1000 V, which could satisfy the needs of the packaging. Electroless copper plating was attempted to complete the metallization of the anodized Al substrate, on which a fine Cu deposit could be obtained when the anodic film was sealed in a bath containing Ni, F ions.     

离子束溅射沉积Co膜光学特性的尺寸效应研究

本文采用离子束溅射沉积了不同厚度的Co膜,利用Lambda-900分光光度计,对不同厚度的Co膜从波长为310nm到1300nm范围测量了薄膜的反射率和透射率.选定波长为310、350、400、430、550、632、800、1200nm时对薄膜的反射率、透射率和吸收率随薄膜厚度变化的关系进行讨论.实验结果显示,Co膜的光学特性都有明显的尺寸效应.对在可见光范围内同一波长时的反射率和透射率随薄膜厚度变化关系的实验结果作于同一图上,发现反射率曲线与透射率曲线都有一个处在网状膜阶段的交点,这个交点对应的厚度作为特征厚度,该厚度可认为是金属薄膜生长从不连续膜进入连续膜的特征判据.     

Flexible a‐Si:H Solar Cells with Spontaneously Formed Parabolic Nanostructures on a Hexagonal‐Pyramid Reflector

Flexible amorphous silicon (a‐Si:H) solar cells with high photoconversion efficiency (PCE) are demonstrated by embedding hexagonal pyramid nanostructures below a Ag/indium tin oxide (ITO) reflector. The nanostructures constructed by nanoimprint lithography using soft materials allow the top ITO electrode to spontaneously form parabolic nanostructures. Nanoimprint lithography using soft materials is simple, and is conducted at low temperature. The resulting structure has excellent durability under repeated bending, and thus, flexible nanostructures are successfully constructed on flexible a‐Si:H solar cells on plastic film. The nanoimprinted pyramid back reflector provides a high angular light scattering with haze reflectance >98% throughout the visible spectrum. The spontaneously formed parabolic nanostructure on the top surface of the a‐Si:H solar cells both reduces reflection and scatters incident light into the absorber layer, thereby elongating the optical path length. As a result, the nanopatterned a‐Si:H solar cells, fabricated on polyethersulfone (PES) film, exhibit excellent mechanical flexibility and PCE increased by 48% compared with devices on a flat substrate.     

Low-dimension structural properties and microindentation studies of ion-beam-sputtered multilayers of Ag/Al films

Artificially modulated silver/aluminum multilayer films with modulation wavelengths Λ between 1.35 and 21.3 nm, and total film thickness of 1 μm were prepared by ion-beam sputtering. The mechanical properties of these films were investigated by a low load muhardness indentation technique. The films displayed increased hardness as the modulation wavelength decreased. X-ray diffraction scans showed well-defined small angle peaks and satellite peaks for high angles indicating a coherent multilayer structure. The hardness enhancement as the modulation wavelength decreases may be partially attributed to the Ag₂Al formation at the interfaces. The high quality of the well-defined layer structure is confirmed by the presence of interference maxima corresponding to the number of bilayers in the low angle diffraction data for films with total film thicknessesess than 33.0 nm.     

Physical and sensing properties of ZnO:F:Al thin films deposited by sol-gel

Fluorine and aluminum-doped zinc oxide thin films, ZnO:F:Al, were prepared on soda-lime glass substrates by the sol-gel method and repeated dip-coating. The effect of the solution ageing and film thickness on the physical characteristics of the films was studied. Two ageing times, namely, two and seven days, and three different thicknesses, in the order of 220, 330, and 520 nm, were the main variables used in this work. As-deposited ZnO:F:Al films showed a high electrical resistivity, however after a vacuum thermal treatment, it was registered a significant decrease. Structural, optical, and morphological characterizations were carried out in vacuum-annealed films. The X-ray diffraction (XRD) patterns revealed that both as-deposited and vacuum-annealed ZnO:F:Al thin films were polycrystalline with a hexagonal wurtzite-type structure with a well-defined (002) diffraction peak, irrespective of the ageing time of the starting solution. The (002) peak shows a proportional increase with the thickness magnitude. An average crystallite size of about 20 nm was estimated using the well-known Scherrer's formula. From the surface morphological study it was observed that the grain size is almost independent of the ageing time of the starting solution, and the film thickness. Films presented an average optical transmittance in the visible range (400-700 nm) in the order of 90%, as well as a band gap of 3.3 eV. The gas-sensing properties of ZnO:F:Al thin films in an atmosphere containing different concentrations of carbon monoxide, and at different operation temperatures were probed. The highest sensitivity registered was of the order of 93%.     

In-line broadband 270 degrees (3lambda/4) chevron four-reflection wave retarders

The net differential phase shift Delta(t) introduced between the orthogonal p and s linear polarizations after four successive total internal reflections inside an in-line chevron dual-Fresnel-rhomb retarder is a function of the first internal angle of incidence phi and prism refractive index n. Retardance of 3lambda/4 (i.e., Delta(t)=270 degrees) is achieved with minimum angular sensitivity when phi=45 degrees and n=1.900822. Several optical glasses with this refractive index are identified. For Schott glass SF66 the deviation of Delta(t) from 270 degrees is < or = 4 degrees over a wavelength range of 0.55 < or = lambda < or = 1.1 microm in the visible and near-IR spectrum. For a SiC prism, whose totally reflecting surfaces are coated with an optically thick MgF(2) film, Delta(t)=270 degrees at two wavelengths: lambda(1)=0.707 microm and lambda(2)=4.129 microm. This coated prism has a maximum retardance error of approximately 5 degrees over > three octaves (0.5 to 4.5 microm) in the visible, near-, and mid-IR spectral range. Another mid-IR 3lambda/4 retarder uses a Si prism, which is coated by an optically thick silicon oxynitride film of the proper composition, to achieve retardance that differs from 270 degrees by < 0.5 degrees over the 3-5 microm spectral range.     

Multilayer coatings with high reflectance in the extreme-ultraviolet spectral range of 50 to 121.6 nm

Multilayer coatings with three layers were designed to yield an increase in normal-incidence reflectance in the extreme ultraviolet over that of the available single-layer coatings. Multilayer coatings based on Al, MgF(2), and either SiC or B(4)C were demonstrated to have higher reflectance than single layers of SiC and B(4)C in the spectral region from 57.9 nm to the H Lyman-alpha line (121.6 nm) and above. The increase in reflectance was higher at wavelengths close to 121.6 nm. Reflectance degraded slightly over time in the same way as for single layers. After a few months, multilayer coatings maintained higher reflectance than their single-layer counterparts.     

Effect on thickness of Al layer in poly-crystalline Si thin films using aluminum(Al) induced crystallization method

The polycrystalline silicon (poly-Si) thin films were prepared by aluminum induced crystallization. Aluminum (Al) and amorphous silicon (a-Si) layers were deposited using DC sputtering and plasma enhanced chemical vapor deposition method, respectively. For the whole process Al properties of bi-layers can be one of the important factors. In this paper we investigated the structural and electrical properties of poly-crystalline Si thin films with a variation of Al thickness through simple annealing process. All samples showed the polycrystalline phase corresponding to (111), (311) and (400) orientation. Process time, defined as the time required to reach 95% of crystalline fraction, was within 60 min and Al(200 nm)/a-Si(400 nm) structure of bi-layer showed the fast response for the poly-Si films. The conditions with a variation of Al thickness were executed in preparing the continuous poly-Si films for solar cell application.     

Contact resistivity measurements of the buried Si-ZnO:Al interface of polycrystalline silicon thin-film solar cells on ZnO:Al

An experimental method is developed for contact resistivity measurements of a buried interface in polycrystalline silicon (poly-Si) thin-film solar cell devices on aluminum doped zinc oxide (ZnO:Al) layers. The solar cell concept comprises a glass substrate covered with a temperature-stable ZnO:Al film as transparent front contact layer, a poly-Si n⁺/p⁻/p⁺ cell, as well as a metal back contact. Glass/ZnO:Al/poly-Si/metal test stripe structures are fabricated by photolithographic techniques with the ZnO:Al stripes locally bared by laser ablation. The high-temperature treatments during poly-Si fabrication, e.g. a several hours lasting high-temperature step at 600 °C, are found to have no detrimental impact on the ZnO:Al/Si interface contact resistivity. All measured ρ_C values range well below 0.4 Ω cm² corresponding to a relative power loss ΔP below 3% for a solar cell with 500 mV open circuit voltage and 30 mA/cm² short circuit current density. By inclusion of a silicon nitride (SiN_x) diffusion barrier between ZnO:Al and poly-Si the electrical material quality of the poly-Si absorber can be significantly enhanced. Even in this case, the contact resistivity remains below 0.4 Ω cm² if the diffusion barrier has a thickness smaller than 10 nm.