Halogen lamp annealing of GaAs for MESFET fabrication

Incoherent light from high-intensity halogen lamps was used for capless annealing of 2-inch GaAs wafers following silicon ion implantation. Fabrication of depletion mode MESFETs on the annealed wafers was used to study the DC characteristics and uniformity achieved with this annealing method. An average mutual transconductance of 110 mS/mm was obtained with MESFET fabricated wafers which were uniformly implanted at 5 × 1012 cm?2 with Si+ at 80 keV and subsequently annealed at 900°C for 2 s. The carrier concentration profiles obtained with this method are shown to be sharper than those obtained with furnace annealed wafers, which in turn results in a sharper device pinch-off voltage.     

Flash-lamp annealing of ion-implanted silicon and its application to solar cells

Xe-lamps were used to anneal p+-implanted silicon. The redistribution of implanted dopants does not occur by flash annealing. The substrate-orientation dependence of electrical activity of implanted dopants between     

Application of a solution proximity annealing technique for fabrication of ion-implanted GaAs integrated circuits

A technique for capless annealing of ion-implanted GaAs, using an arsenic-saturated solution of Sn and Ga in close proximity to the wafer, has been applied to the fabrication of GaAs integrated circuits. The IC processing technology utilizes a self-aligned T-shaped refractory gate approach for the fabrication of both enhancement- and depletion-mode MESFET's. Using the solution proximity annealing technique, excellent threshold voltage uniformities (standard deviation = 26 mV) have been obtained for enhancement-mode devices using commercial substrates. This process technology has resulted in the fabrication of divide-by-16 circuits in both SDFL and DCFL logic implementations, as well as enhancement/depletion (E/D) ring oscillators (Lg= 2 µm) with propagation delays as low as 45 ps/gate and concomitant power consumptions of 2 mW/gate. This technique can also be applied, by suitable choice of the solution constituents, to capless annealing of other III-V semiconductors such as InP and GaInAs.     

Enhanced infrared transmission of GZO film by rapid thermal annealing for Si thin film solar cells

Ga doped ZnO (GZO) films prepared by sputtering at room temperature were rapid thermal annealed (RTA) at elevated temperatures. With increasing annealing temperature up to 570°C, film transmission enhanced significantly over wide spectral range especially in infrared region. Hall effect measurements revealed that carrier density decreased from ∼8 × 10²⁰ to ∼ 3 × 10²⁰ cm⁻³ while carrier mobility increased from ∼15 to ∼28 cm²/Vs after the annealing, and consequently low film resistivity was preserved. Hydrogenated microcrystalline Si (µc‐Si:H) and microcrystalline Si_1‐xGe_x (µc‐Si_1‐xGe_x:H, x = 0.1) thin film solar cells fabricated on textured RTA‐treated GZO substrates demonstrated strong enhancement in short‐circuit current density due to improved spectral response, exhibiting quite high conversion efficiencies of 9.5% and 8.2% for µc‐Si:H and µc‐Si_0.9Ge_0.1:H solar cells, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

New technique for fabrication of low voltage Si Zener diodes

A new technique for fabrication of low voltage Si Zener diodes is suggested, which consists of two successive diffusions (first a deep phosphorus diffusion and then a shallow boron diffusion) into an n-type Si epitaxial layer. Also, a new analytical expression for differential resistance of low voltage Si Zener diodes in the breakdown region is derived, which describes remarkably well the experimental results.     

太阳能电源低压钠灯智能控制器的设计

设计一种采用低功耗单片机P87LPC767作为控制回路核心,低压钠灯为负载的太阳能电源智能控制器.系统在P87LPC767单片机的控制下,能将太阳能电池方阵转换的直流电进行有效存储和合理使用,具有环保节能的双重效果.实现了充放电过程的自动控制功能,防短路、防过载、防反接、充满和过放自动关断、恢复等保护功能,以及具有充电指示、蓄电池状态、负载及各种故障指示等功能.最后结合实验证明了该智能控制器系统运行稳定可靠.     

Optimization of the deposition and annealing conditions of fluorine-doped indium oxide films for silicon solar cells

Fluorine-doped indium oxide (IFO) films are deposited onto (pp ⁺)Si and (n ⁺ nn ⁺)Si structures made of single-crystal silicon by ultrasonic spray pyrolysis. The effect of the IFO deposition time and annealing time in an argon atmosphere with methanol vapor on the IFO chemical composition, the photovoltage and fill factor of the Illumination-U _oc curves of IFO/(pp ⁺)Si structures, and the sheet resistance of IFO/(n ⁺ nn ⁺)Si structures, correlating with the IFO/(n ⁺)Si contact resistance, is studied. The obtained features are explained by modification of the properties of the SiO _x transition layer at the IFO/Si interface during deposition and annealing. Analysis of the results made it possible to optimize the fabrication conditions of solar cells based on IFO/(pp ⁺)Si heterostructures and to increase their efficiency from 17% to a record 17.8%.     

Thermal annealing of proton-irradiated silicon solar cells

Solar cells made from 1.5- and 10-Ωċcm p-type silicon, with silver-titanium evaporated electrodes, were irradiated by 4.6-MeV protons at room temperature to fluences ranging from 1 × 10¹⁰to 1 × 10¹²protons/cm². The photovoltaic current-voltage characteristics, the photovoltaic spectral response, and the minority carrier diffusion length were studied as the solar cells were annealed isochronally to temperatures up to 600°C. The proton radiation damage annealed in two stages, the first occurring between 50° and 150°C, and the second between 350° and 450°C. The removal of proton damage in this manner differs markedly from the annealing reported for 1-MeV electron damage, where practically no recovery of the photovoltaic properties is observed below 350°C. At any selected annealing temperature, the 10-Ω ċ cm cells were observed to recover to a slightly greater degree than the 1.5-Ω ċ cm type.     

Design criteria for Si point-contact concentrator solar cells

Design criteria for concentrator solar cells are presented for the highly three-dimensional case of backside point-contact solar cells. A recent new experimental result, a 28-percent efficient cell (25°C, 15-W/cm²incident power) is used as a case study of the dependences of the recombination components and the carrier density gradients on the geometrical design parameters. The optimum geometry is found to depend upon the intended design power density as well as the attainable physical parameters allowed by the fabrication techniques utilized. Modeling projections indicate that an ultimate efficiency of 30.6 percent (36 W/cm², 300 K) is achievable using the diffused emitters presently employed on these cells. Incorporation of results from the study of polycrystalline emitters could improve these efficiencies toward 31.7 percent.     

Simple fabrication of perovskite solar cells using lead acetate as lead source at low temperature

We reported a simple one-step, low-temperature solution-processed technique to fabricate perovskite solar cells using lead acetate as the lead source. Solvent annealing was applied for grain growth to obtain better morphology. Uniform perovskite films without pinholes can be obtained by solvent annealing for 5 min at 100 °C. Planar perovskite solar cells based on the high quality perovskite films deliver power conversion efficiency up to 12.71% with negligible hysteresis and good reproducibility. In addition, the substrate surfaces have little effect on the crystallization of perovskite when lead acetate was used, leading to uniform films on different substrates, which can provide a wide choice of substrates and interfacial materials.     

Improvement of performance deviation and productivity of MOSFETs with gate length below 30 nm by flash lamp annealing

The impact of new flash lamp annealing (FLA) technology, which both minimizes diffusion to yield a shallow junction and realizes low sheet resistivity, is investigated based on MOSFET fabrication and computer simulations. Productivity can be improved since FLA makes it possible to employ higher acceleration energy ion implantation and higher throughput. The MOSFET performance can be improved and its deviation suppressed by using FLA. In analyzing MOSFETs with gate length (L) of 20 nm by computer simulations, it was clarified that in contrast to spike annealing, the shallow junction realized by applying FLA to pMOSFET fabrication enabled the suppression of |I/sub off/| with a low channel surface dopant concentration. This provided a higher mobility value and a higher drive current. FLA is promising for improving the performance and productivity of sub-30-nm gate-length MOSFETs.     

Review of roll-to-roll fabrication techniques for colloidal quantum dot solar cells

Colloidal quantum dots (CQDs) are of great interest to photovoltaic (PV) technologies as they possess the benefits of solution-processability, size-tunability, and roll-to-roll manufacturability, as well as unique capabilities to harvest near-infrared (NIR) radiation. During the last decade, lab-scale CQD solar cells have achieved rapid improvement in the power conversion efficiency (PCE) from ~1% to 18%, which will potentially exceed 20% in the next few years and approach the performance of other PV technologies, such as perovskite solar cells and organic solar cells. In the meanwhile, CQD solar cells exhibit long lifetimes either under shelf storage or continuous operation, making them highly attractive to industry. However, in order to meet the industrial requirements, mass production techniques are necessary to scale up the fabrication of those lab devices into large-area PV modules, such as roll-to-toll coating. This paper reviews the recent developments of large-area CQD solar cells with a focus on various fabrication methods and their principles. It covers the progress of typical large-area coating techniques, including spray coating, blade coating, dip coating, and slot-die coating. It also discusses next steps and new strategies to accomplish the ultimate goal of the low-cost large-area fabrication of CQD solar cells and emphasizes how artificial intelligence or machine learning could facilitate the developments of CQD solar cell research.     

Spray coating methods for polymer solar cells fabrication: A review

The main focus of this review article is the introduction of relevant parameters in spray coating processes to provide better understanding on controlling the morphology of spray coated thin films for producing high performance polymer solar cells (PSC). Three main parameters have been identified as major influences on the spray coating processes. These are nozzle to substrate distance, solvent and mixed solvents effects, and substrate temperature and annealing treatment. Such spray coating techniques show great potential for large scale production, since these methods have no limitation in substrate size and low utilization of polymers which is promising to substitute the conventional spin coating methods. Currently available printing and coating methods are also briefly discussed in this review.     

聚合物太阳能电池制备技术的研究进展

聚合物太阳能电池具有质量轻、柔性、可大面积制备等优点,成为当前能源领域的研究热点。光活性层是聚合物太阳能电池的核心部件,扮演着将光子转换为电荷的角色。因此,它的制备技术与工艺过程是影响光电转换性能的一个重要因素。本文从光活性层及与其相关的功能层的制备角度出发,综述了旋涂、喷涂、卷对卷、喷墨打印四种技术在聚合物太阳能电池领域的研究进展,最后对这四种技术在有机光伏领域的发展进行了展望。     

A comparison of graphite and AlN caps used for annealing ion-implanted SiC

The SiC wafers implanted with Al were capped with AlN, C, or AlN and C and were annealed at temperatures as high as 1700°C to examine their ability to act as annealing caps. As shown previously, the AlN film was effective up to 1600°C, as it protected the SiC surface, did not react with it, and could be removed selectively by a KOH etch. However, it evaporated too rapidly at the higher temperatures. Although the C did not evaporate, it was not a more effective cap because it did not prevent the out-diffusion of Si and crystallized at 1700°C. The crystalline film had to be ion milled off, as it could not be removed in a plasma asher, as the C films annealed at the lower temperatures were. A combined AlN/C cap also was not an effective cap for the 1700°C anneal as the N or Al vapor blew holes in it, and the SiC surface was rougher after the dual cap was removed than it was after annealing at the lower temperatures.     

GaAs solar cells grown on Si substrates for space use

GaAs single‐junction and InGaP/GaAs multi‐junction thin‐film solar cells fabricated on Si substrates have great potential for high‐efficiency, low‐cost, lightweight and large‐area space solar cells. Heteroepitaxy of GaAs thin films on Si substrates has been examined and high‐efficiency GaAs thin‐film solar cells with total‐area efficiencies of 18·3% at AM0 and 20·0% at AM 1·5 on Si substrates (GaAs‐on‐Si solar cells) have been fabricated. In addition, 1‐MeV electron irradiation damage to GaAs‐on‐Si cells has been studied. The GaAs‐on‐Si cells are found to show higher end‐of‐life efficiency than the conventional GaAs cells fabricated on GaAs substrates (GaAs‐ on‐GaAs cells) under high‐fluence 1‐MeV electron irradiation of more than 1 × 10¹⁵ cm⁻². The first space flight to make use of them has been carried out. Forty‐eight 2 × 2 cm GaAs‐on‐Si cells with an average AM0 total‐area efficiency of 16·9% have been evaluated in the Engineering Test Satellite No.6 (ETS‐VI). The GaAs‐on‐Si cells have been demonstrated to be more radiation‐resistant in space than GaAs‐on‐GaAs cells and 50, 100 and 200‐μm‐thick Si cells. These results show that the GaAs‐on‐Si single‐junction and InGaP/GaAs‐on‐Si multi‐junction cells have great potential for space applications. Copyright © 2001 John Wiley & Sons, Ltd.     

Heterojunction solar cells of SnO2/Si

Heterojunction solar cells (HJSC’s), fabricated by electron beam evaportaion of SnO₂ films onto monocrystalline and polycrystalline Si substrates, show conversion efficiencies as high as 9.9%, fill factors of 0.64, and open circuit voltages of 525 mV under AMI simulated irradiation. The SnO₂, an n-type semiconductor, acts as a transparent window to solar irradiation and as an antireflection coating of the Si, and it provides the band bending in the Si necessary for photovoltaic conversion. The SnO₂ films, nominally 50 nm thick, have conductivities of the order of 10³(Ω-cm)⁻¹ so that the film makes a good electrical contact between the junction and the metallic front contacts. Measurements of C⁻²-V and I-V characteristics are consistent with heterojunction theory, and the data imply an electron affinity of the SnO₂ of approximately 0.8 eV greater than the electron affinity of Si. This value limits the open circuit voltage of HJSC’s made on p-type substrates to values too small for useful photovoltaic conversion. The predominant dark current mechanism of units of n-type substrates at room temperature and forward bias in the range of 0.3−0.5 V is electron-hole recombination in the transition region. The experimentally determined activation energy is 0.51 eV, approximately E_g/2. At forward voltages below 0.3 V, multistep tunneling via interband states predominates. The photocurrent apparently depends on interface states through which the photogenerated holes in the Si recombine with electrons in the SnO₂.     

Influence of post-synthesis annealing on PbS quantum dot solar cells

Colloidal quantum dots (CQDs) are attractive materials for optoelectronic applications due to their low-cost, facile processing and size-dependent band-gap tunability. Solution-processed organic, inorganic and hybrid ligand-exchange techniques have been widely applied in QDs-based solar cells (QDSCs) to improve the power conversion efficiency (PCE). Till now, however, few have been reported to date the influence of post-synthesis annealing on the electrical characteristics of the PbS QDSCs. To reduce the influence of diffusion length, in this work, we present the thermal annealing treatment effect on the device performance of a typical heterojunction solar cell ITO/ZnO/PbS/Au with a relatively thinner active layer. By changing the annealing temperatures during the post-synthesis processes, we found its PCE increase from 3.26% to 4.52% after annealing at 140 °C, showing a 38.6% enhancement due to a dramatic enhancement of short circuit-current density (J_SC) but a slight decrement of open-circuit voltage (V_OC), and also, the mechanisms underneath for the enhanced performance are discussed in details.     

Efficiency enhancement of polymer solar cells by post-additional annealing treatment

We adopt the post-additional thermal annealing (PATA) process to optimize the performance of the polymer solar cells (PSCs) with an active layer composed of a blend of regioregular poly (3-hexythiophene) (RR-P3HT) and fullerenes. It is found that compared with general annealing process, the crystallinity of RR-P3HT by PATA is enhanced, and the absorption peak is raised obviously at ～500 nm after PATA. With the optimized annealing conditions, the device shows an enhancement of 31% in short circuit current density, 5% in open circuit voltage (Voc), and 11% in the power conversion efficiency (PCE) compared with that of the general annealing device.     

Surface nanocrystalline Si structure and its surface passivation for highly efficient black Si solar cells

19.5% conversion efficiency crystalline silicon (Si) solar cells having simple structure without antireflection coating have been fabricated using the surface structure chemical transfer method which produces a nanocrystalline Si layer simply by contacting catalytic platinum with Si wafers in hydrogen peroxide plus hydrofluoric acid solutions. The reflectivity becomes less than 3% after the surface structure chemical transfer method due to formation of black Si. Deposition of phosphosilicate glass and heat treatment at 925 °C performed for formation of pn‐junction effectively passivate the nanocrystalline Si surface. With this phosphosilicate glass passivation plus the hydrogen treatment at 400 °C, the internal quantum efficiency is greatly improved and reaches 81% at a wavelength of 400 nm. Analysis of ellipsometry data shows that incident light with wavelength shorter than 400 nm is almost completely absorbed by the nanocrystalline Si layer. The high internal quantum efficiency for short wavelength light is attributed to effective surface passivation and the nanocrystalline Si layer band‐gap energy which decreases with the distance from the top of the network structure of the nanocrystalline Si layer. Copyright © 2017 John Wiley & Sons, Ltd.