Showing papers on "Amorphous silicon published in 2020"
TL;DR: In this paper, the influence of the MoOx and intrinsic a-Si:H thicknesses on current-voltage properties and discuss transport and performance-loss mechanisms is discussed. But the authors focus on the front-side hole-selective layer.
163 citations
TL;DR: In this paper, the development status of high-efficiency crystalline silicon (c-Si) heterojunction solar cells, from the materials to devices, mainly including hydrogenated amorphous silicon (a-Si:H) based silicon heterjunction technology, polycrystalline silicon based carrier selective passivating contact technology, metal compounds and organic materials based dopant-free contact technology are reviewed.
Abstract: Photovoltaic (PV) technology offers an economic and sustainable solution to the challenge of increasing energy demand in times of global warming. The world PV market is currently dominated by the homo-junction crystalline silicon (c-Si) PV technology based on high temperature diffused p-n junctions, featuring a low power conversion efficiency (PCE). Recent years have seen the successful development of Si heterojunction technologies, boosting the PCE of c-Si solar cells over 26%. This article reviews the development status of high-efficiency c-Si heterojunction solar cells, from the materials to devices, mainly including hydrogenated amorphous silicon (a-Si:H) based silicon heterojunction technology, polycrystalline silicon (poly-Si) based carrier selective passivating contact technology, metal compounds and organic materials based dopant-free passivating contact technology. The application of silicon heterojunction solar cells for ultra-high efficiency perovskite/c-Si and III-V/c-Si tandem devices is also reviewed. In the last, the perspective, challenge and potential solutions of silicon heterojunction solar cells, as well as the tandem solar cells are discussed.
112 citations
TL;DR: In this article, the authors reported a certified efficiency of up to 2511% for silicon heterojunction (SHJ) solar cells on a full size n-type M2 monocrystalline-silicon (c-Si) wafer.
87 citations
20 May 2020
TL;DR: In this paper, an approach to overcome the refractive index mismatch by using an intermediate layer of hydrogenated amorphous silicon, followed by the microtransfer printing of a prefabricated III-V semiconductor optical amplifier is presented.
Abstract: The development of ultralow-loss silicon-nitride-based waveguide platforms has enabled the realization of integrated optical filters with unprecedented performance. Such passive circuits, when combined with phase modulators and low-noise lasers, have the potential to improve the current state of the art of the most critical components in coherent communications, beam steering, and microwave photonics applications. However, the large refractive index difference between silicon nitride and common III-V gain materials in the telecom wavelength range hampers the integration of electrically pumped III-V semiconductor lasers on a silicon nitride waveguide chip. Here, we present an approach to overcome this refractive index mismatch by using an intermediate layer of hydrogenated amorphous silicon, followed by the microtransfer printing of a prefabricated III-V semiconductor optical amplifier. Following this approach, we demonstrate a heterogeneously integrated semiconductor optical amplifier on a silicon nitride waveguide circuit with up to 14 dB gain and a saturation power of 8 mW. We further demonstrate a heterogeneously integrated ring laser on a silicon nitride circuit operating around 1550 nm. This heterogeneous integration approach would not be limited to silicon-nitride-based platforms: it can be used advantageously for any waveguide platform with low-refractive-index waveguide materials such as lithium niobate.
81 citations
TL;DR: This work applied direct laser-induced periodic surface structuring to drive the phase transition of amorphous silicon into nanocrystalline Si imprinted as regular arrangement of Si nanopillars passivated with a SiO2 layer to form diverse hierarchical LIPSSs.
Abstract: Here, we applied direct laser-induced periodic surface structuring to drive the phase transition of amorphous silicon (a-Si) into nanocrystalline (nc) Si imprinted as regular arrangement of Si nanopillars passivated with a SiO2 layer. By varying the laser beam scanning speed at a fixed pulse energy, we successfully tailored the resulting unique surface morphology of the formed LIPSSs that change from ordered arrangement of conical protrusions to highly uniform surface gratings, where sub-wavelength scale ripples decorate the valleys between near-wavelength scale ridges. Along with the surface morphology, the nc-Si/SiO2 volume ratio can also be controlled via laser processing parameters allowing the tailoring of the optical properties of the produced textured surfaces to achieve anti-reflection performance or partial transmission in the visible spectral range. Diverse hierarchical LIPSSs can be fabricated and replicated over large-scale areas opening a pathway for various applications including optical sensors, nanoscale temperature management, and solar light harvesting. By taking advantage of good wettability, enlarged surface area and remarkable light-trapping characteristics of the produced hierarchical morphologies, we demonstrated the first LIPSS-based surface enhanced fluorescent sensor that allowed the identification of metal cations providing a sub-nM detection limit unachievable by conventional fluorescence measurements in solutions.
59 citations
TL;DR: In this article, a bifacial passivation strategy for the metal/Si interface of an inverted-MIS photoelectrode, featuring a bi-layer stack consisting of amorphous silicon (a-Si) for passivating the silicon surface and a metal oxide (TiO2), was proposed.
Abstract: Silicon-based (Si-based) junctions have been widely investigated in recent years as photoelectrochemical (PEC) water splitting photoelectrodes, including buried junctions and metal–insulator–semiconductor (MIS) Schottky junctions. However, Si-based MIS photoelectrodes suffer from low performance for the PEC oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) because of the dilemma that a thin insulator cannot provide enough interfacial passivation while a thick insulator will block the transport of charge carriers. Another trade-off is the fact that the photovoltage extracted from the band offset between the metal and semiconductor will be counteracted by the parasitic light absorption of the metal layer, sacrificing the saturation photocurrent. This paper describes the design and realization of a bifacial passivation strategy for the metal/Si interface of an MIS photoelectrode, featuring a bi-layer stack consisting of amorphous silicon (a-Si) for passivating the silicon surface and a metal oxide (TiO2) for passivating the metal surface. Upon the bifacial passivation of both a-Si and TiO2, the minority carrier lifetime of the Si MIS photoanode was significantly improved from 18 to 2360 μs. Enabled by this extremely long minority carrier lifetime, it becomes possible to place the MIS junction on the back side of a Si substrate to construct an inverted-MIS (I-MIS) structure to eliminate the parasitic light absorption of traditional Si MIS photoelectrodes. The obtained photoelectrode exhibits an excellent onset potential of 0.85 V and 0.62 V vs. reversible hydrogen electrode (RHE) for the OER and HER, respectively. Eventually, unprecedented applied bias photon-to-current efficiencies (ABPE) of 3.91% and 12.66% were obtained by Si MIS and Si I-MIS, which are the highest among MIS-based photoanodes and photocathodes, with 30 h and 108 h stable operation. When pairing the Si I-MIS photocathode with a BiVO4 photoanode to form a PEC membrane-free tandem cell, an unbiased solar-to-hydrogen conversion efficiency of 1.9% is achieved.
58 citations
TL;DR: In this article, a back surface field layer made of low-cost and widely available barium silicide (BaSi2) with a thickness of 0.3µm is introduced for the first time into the basic CIGS solar cell structure consisting of Al/ZnO/CdS/CIGS/Mo, with fluorine-doped tin oxide (FTO) as the window layer.
Abstract: Conventional copper indium gallium diselenide (CIGS)-based solar cells offer higher efficiency than other second-generation technologies such as hydrogenated amorphous silicon (a-Si:H)- or cadmium telluride (CdTe)-based solar cells, but higher manufacturing cost due to the use of the rare metals indium and gallium. The purpose of the work presented herein is to improve the efficiency of such devices by using cheaper materials. Accordingly, a back-surface field layer made of low-cost and widely available barium silicide (BaSi2) with a thickness of 0.3 µm is introduced for the first time into the basic CIGS solar cell structure consisting of Al/ZnO/CdS/CIGS/Mo, resulting in the alternative structure of Al/FTO/CdS/CIGS/BaSi2/Mo, with fluorine-doped tin oxide (FTO) as the window layer. One-dimensional simulations of the solar cell capacitance are employed to study the photovoltaic parameters such as the power conversion efficiency, short-circuit current density, open-circuit voltage, fill factor, and quantum efficiency of the devices. The thickness of the CIGS absorber layer is varied from 0.1 to 3 µm to optimize the device. Besides, the effects of the acceptor ion and bulk defect densities in the CIGS absorber layer, cell resistances, and operating temperature on the overall performance are also investigated. The proposed structure offers an efficiency of 26.24% with a thin CIGS layer of only 0.8 µm. In addition to reduced CIGS thickness and cost, the presented approach results in CIGS solar cells with enhanced performance compared with previously reported conventional designs.
54 citations
TL;DR: Basic material properties and device structures of TFTs in commercial displays are explored, and the potential of atomically thin layered transition metal dichalcogenides as next-generation channel materials is discussed.
Abstract: As the need for super-high-resolution displays with various form factors has increased, it has become necessary to produce high-performance thin-film transistors (TFTs) that enable faster switching and higher current driving of each pixel in the display. Over the past few decades, hydrogenated amorphous silicon (a-Si:H) has been widely utilized as a TFT channel material. More recently, to meet the requirement of new types of displays such as organic light-emitting diode displays, and also to overcome the performance and reliability issues of a-Si:H, low-temperature polycrystalline silicon and amorphous oxide semiconductors have partly replaced a-Si:H channel materials. Basic material properties and device structures of TFTs in commercial displays are explored, and then the potential of atomically thin layered transition metal dichalcogenides as next-generation channel materials is discussed.
47 citations
TL;DR: It is found that the chemical composition and thickness of the solid/electrolyte interphase layer (SEI) continuously change during the charging/discharging cycles.
Abstract: This work focuses on the mechanisms of interfacial processes at the surface of amorphous silicon thin-film electrodes in organic carbonate electrolytes to unveil the origins of the inherent nonpassivating behavior of silicon anodes in Li-ion batteries. Attenuated total reflection Fourier-transform infrared spectroscopy, X-ray absorption spectroscopy, and infrared near-field scanning optical microscopy were used to investigate the formation, evolution, and chemical composition of the surface layer formed on Si upon cycling. We found that the chemical composition and thickness of the solid/electrolyte interphase (SEI) layer continuously change during the charging/discharging cycles. This SEI layer "breathing" effect is directly related to the formation of lithium ethylene dicarbonate (LiEDC) and LiPF6 salt decomposition products during silicon lithiation and their subsequent disappearance upon delithiation. The detected appearance and disappearance of LiEDC and LiPF6 decomposition compounds in the SEI layer are directly linked with the observed interfacial instability and poor passivating behavior of the silicon anode.
45 citations
TL;DR: In this paper, double antireflection coatings (ARCs) of SiNx and SiOx were applied to the front a-Si:H passivation layer to improve the photovoltaic performance.
41 citations
TL;DR: In this article, a plasma assisted N2O gas oxidation (PANO) method was developed to prepare the ultrathin silicon oxide (SiOx) for polysilicon (poly-Si) passivated contact.
TL;DR: Three nanotextured plasmonic metal BRs underneath flexible thin film amorphous silicon solar cells are systematically investigated and demonstrate excellent light harvesting capability in the long wavelength region.
Abstract: Nanostructured metal back reflectors (BRs) are playing an important role in thin-film solar cells, which facilitates an increased optical path length within a relatively thin absorbing layer. In this study, three nanotextured plasmonic metal (copper, gold, and silver) BRs underneath flexible thin-film amorphous silicon solar cells are systematically investigated. The solar cells with BRs demonstrate an excellent light harvesting capability in the long-wavelength region. With the combination of hybrid cavity resonances, horizontal modes, and surface plasmonic resonances, more incident light is coupled into the photoactive layer. Compared to the reference cells, the three devices with plasmonic BRs show lower parasitic absorptions with different individual absorption distributions. Both experimental and simulated results indicate that the silver BR cells delivered the best performance with a promising power conversion efficiency of 7.26%. These rational designs of light harvesting nanostructures provide guidelines for high-performance thin-film solar cells and other optoelectronic devices.
TL;DR: In this article, the authors investigated the evolution of optoelectrical parameters by varying the main deposition conditions to achieve layers with refractive index below 2.2 and dark conductivity above 1.00.
Abstract: Hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) layers exhibit promising optoelectrical properties for carrier-selective-contacts in silicon heterojunction (SHJ) solar cells. However, achieving high conductivity while preserving crystalline silicon (c-Si) passivation quality is technologically challenging for growing thin layers (less than 20 nm) on the intrinsic hydrogenated amorphous silicon ((i)a-Si:H) layer. Here, we present an evaluation of different strategies to improve optoelectrical parameters of SHJ contact stacks founded on highly transparent nc-SiOx:H layers. Using plasma-enhanced chemical vapor deposition, we firstly investigate the evolution of optoelectrical parameters by varying the main deposition conditions to achieve layers with refractive index below 2.2 and dark conductivity above 1.00 S/cm. Afterwards, we assess the electrical properties with the application of different surface treatments before and after doped layer deposition. Noticeably, we drastically improve the dark conductivity from 0.79 to 2.03 S/cm and 0.02 to 0.07 S/cm for n- and p-contact, respectively. We observe that interface treatments after (i)a-Si:H deposition not only induce prompt nucleation of nanocrystals but also improve c-Si passivation quality. Accordingly, we demonstrate fill factor improvement of 13.5%abs from 65.6% to 79.1% in front/back-contacted solar cells. We achieve conversion efficiency of 21.8% and 22.0% for front and rear junction configurations, respectively. The optical effectiveness of contact stacks based on nc-SiOx:H is demonstrated by averagely 1.5 mA/cm2 higher short-circuit current density thus nearly 1%abs higher cell efficiency as compared with the (n)a-Si:H.
TL;DR: In this article, a carbon nanotube ink is spin coated directly onto a silicon wafer to serve simultaneously as a hole extraction layer, but also to passivate interfacial defects.
Abstract: Traditional silicon solar cells extract holes and achieve interface passivation with the use of a boron dopant and dielectric thin films such as silicon oxide or hydrogenated amorphous silicon. Without these two key components, few technologies have realized power conversion efficiencies above 20%. Here, a carbon nanotube ink is spin coated directly onto a silicon wafer to serve simultaneously as a hole extraction layer, but also to passivate interfacial defects. This enables a low‐cost fabrication process that is absent of vacuum equipment and high‐temperatures. Power conversion efficiencies of 21.4% on an device area of 4.8 cm$^{2}$ and 20% on an industrial size (245.71 cm$^{2}$) wafer are obtained. Additionally, the high quality of this passivated carrier selective contact affords a fill factor of 82%, which is a record for silicon solar cells with dopant‐free contacts. The combination of low‐dimensional materials with an organic passivation is a new strategy to high performance photovoltaics.
TL;DR: In this article, the effect of variations in the thickness of the a-Si:H(i) layer and the indium tin oxide (ITO) doping on the contact resistivity of the hole contact stack was investigated.
Abstract: In silicon heterojunction solar cells made with high-lifetime wafers, resistive losses in the contacts dominate the total electrical power loss. Moreover, it is widely believed that the hole contact stack—a-Si:H(i)/a-Si:H(p)/ITO/Ag—is responsible for more of this power loss than the electron contact stack. In this article, we vary the a-Si:H(i) layer thickness, the a-Si:H(p) layer thickness and doping, and the indium tin oxide (ITO) doping, and determine the effect of each variation on the contact resistivity of the hole contact stack. In addition, we make complete solar cells with the same variations and correlate their series resistivity to the hole contact resistivity. We find that the contact resistivity is most sensitive to the thickness of the a-Si:H(i) layer and the oxygen partial pressure during ITO sputtering. Increasing the former from 4 to 16 nm results in a fourfold increase in contact resistivity, whereas increasing the latter from 0.14 to 0.85 mTorr raises the contact resistivity almost 30-fold. Optimized conditions produce a contact resistivity of 0.10 Ωcm2, while maintaining an implied open-circuit voltage of 720 mV measured on cell precursors, which is the lowest contact resistivity value reported in the literature for an a-Si:H hole contact.
TL;DR: In this paper, the authors report on novel amorphous carbon phases containing high fraction of sp3 bonded atoms recovered after compressing fullerene C60 to previously unexplored high pressure and temperature.
Abstract: Carbon is likely the most fascinating element of the periodic table because of the diversity of its allotropes stemming from its variable (sp, sp2, and sp3) bonding motifs. Exploration of new forms of carbon has been an eternal theme of contemporary scientific research. Here we report on novel amorphous carbon phases containing high fraction of sp3 bonded atoms recovered after compressing fullerene C60 to previously unexplored high pressure and temperature. The synthesized carbons are the hardest and strongest amorphous materials known to date, capable of scratching diamond crystal and approaching its strength which is evidenced by complimentary mechanical tests. Photoluminescence and absorption spectra of the materials demonstrate they are semiconductors with tunable bandgaps in the range of 1.5-2.2 eV, comparable to that of amorphous silicon. A remarkable combination of the outstanding mechanical and electronic properties makes this class of amorphous carbons an excellent candidate for photovoltaic applications demanding ultrahigh strength and wear resistance.
TL;DR: In this paper, an ultra-thin n-type hydrogenated nanocrystalline silicon oxide (nc-SiOx:H) film was used to replace amorphous silicon [a-Si:H (n)] as electron transport layer (ETLTL) in rear-junction silicon heterojunction (SHJ) solar cell to reduce front parasitic absorption.
TL;DR: In this article, a 2×2 circularly polarized microstrip slot array antenna integrated with amorphous silicon solar cells using a stacked design method was measured, and the results showed that the gain of the antenna is almost unchanged after the integration of the AMOS cells and the axial ratio decreases to 1.4 dB.
Abstract: This letter describes the integration of microstrip slot array antenna with amorphous silicon solar cells. To appraise the antenna, a 2×2 circularly polarized microstrip slot array antenna integrated with amorphous silicon solar cells using a stacked design method was measured. The results show that the gain of the antenna is almost unchanged after the integration of the amorphous silicon solar cells and the axial ratio decreases to 1.4 dB. The amorphous silicon solar cells and the microstrip slot array antenna are perfectly combined, the interference between the solar cells and the antenna is minimal. The integration saves a lot of space, and has the ability to self-sustaining power generation, thus providing reliable and long-term communication for various satellite communication systems.
TL;DR: In this paper, the selectivity of TiOx layers is found to be widely tunable from electron to hole selective depending on deposition conditions, postdeposition treatments, and work function of the metal electrode used.
TL;DR: In this article, the authors demonstrate that conventional alkaline-based wet-chemical etching processes can be tuned to produce dense, spatially homogeneous, and uniformly sized sub-micrometer pyramids.
21 Jul 2020
TL;DR: In this article, the authors demonstrate high efficiency wavelength conversion via four wave mixing in amorphous silicon carbide ring resonators with a loaded quality factor of 70 000 and achieved −21 dB conversion efficiency with 15 mW pump power.
Abstract: We demonstrate high efficiency wavelength conversion via four wave mixing in amorphous silicon carbide ring resonators with a loaded quality factor of 70 000. Owing to the high quality factor and high nonlinearity of amorphous silicon carbide, −21 dB conversion efficiency is achieved with 15 mW pump power. Moreover, the thermo-optic coefficient (TOC) of amorphous silicon carbide is measured to be 1.4 × 10−4/°C at telecommunication wavelengths. Taking advantage of the high TOC, we demonstrate optical bistability in the silicon carbide ring resonator. This work presents amorphous silicon carbide as a promising platform for applications in optical signal processing.
TL;DR: In this article, the authors proposed a transparent conductive electrode (TCE) for silicon heterojunction solar cells (Si-HJSCs) and tested over devices with area up to 4 cm2 realized on n-type c-Si wafers with three different p-type emitters facing the dry-transferred graphene stack.
TL;DR: In this article, the thin intrinsic hydrogenated amorphous silicon layer was optimized by controlling the deposition temperature and the silane-to-hydrogen dilution ratio to reduce the surface saturation current densities.
TL;DR: In this article, the influence of plasma enhanced chemical vapor deposition (PECVD) deposition temperature on heavily doped silicon based (doped-Si/SiOx) passivating contacts for silicon solar cells is described.
TL;DR: In this article, the performance of nanocrystalline silicon was investigated for high capacity anode for Li-ion batteries, where the authors reported a discharge capacity of 3090 mµ g−1 at C/5 rate and a capacity retention of around 2250 m µg−1 after 50 cycles.
TL;DR: In this article, a one-diode model is proposed to represent the current-voltage curves of both crystalline and thin-film photovoltaic modules, and the model parameters are calculated from the information contained in the datasheets issued by manufactures by means of simple iterative procedures that do not require the assumption of simplifying hypotheses.
TL;DR: In this paper, a perovskite (CH3NH3PbI3)/FeSi2(p-i-n structure) 2-terminal (2-T) monolithic tandem solar cell is proposed and investigated using AFORS-HET v2.5 1D simulator.
Abstract: A multijunction or tandem technique comprising a wide bandgap top cell and a narrow bandgap bottom cell may be a major stepping stone in an attempt to obtain high-efficiency solar cells. However, easier said than done, it takes a lot to correctly optimize the structure of all the involved layers so as to possibly obtain the desired results. In this paper, a perovskite (CH3NH3PbI3)/FeSi2 (p-i-n structure) 2-terminal (2-T) monolithic tandem solar cell is proposed and investigated using AFORS-HET v2.5 1D simulator. A hydrogenated amorphous silicon (a-Si:H)/hydrogenated microcrystalline silicon oxide (µc-Si1−xOx:H) tunnel recombination junction is employed to interconnect both perovskite and FeSi2 solar cell for current matching. The influence of both top and bottom absorber layer thickness is analyzed to optimize the device performance. The study reveals an optimized 26.3% efficient perovskite/FeSi2 monolithic tandem solar cell with JSC (21.4 mA cm−2), VOC (1.63 V), and FF (74.86%). The results in this paper suggest FeSi2 material with 0.87 eV bandgap as an alternative for narrow bandgap bottom cell for the perovskite-based tandem solar cells so as to obtain much higher efficiencies.
TL;DR: In this paper, the insertion of a metasurface based on a cross-patterned ITO contact film, where the crosses are filled with nanospheres was proposed.
TL;DR: In this article, the authors demonstrate that for commercially viable solar-grade silicon, thinner wafers and surface saturation current densities below 1 fA cm−2, are required to significantly increase the practical efficiency limit of solar cells up to 0.6% absolute.
Abstract: Multiple silicon solar cell technologies have surpassed or are close to surpassing 26% efficiency. Dielectric and amorphous silicon-based passivation layers combined with minimal metal/silicon contact areas were responsible for reducing the surface saturation current density below 3 fA cm−2. At open-circuit, in passivated contact solar cells, the recombination is mainly from fundamental mechanisms (Auger and radiative) representing over 3/4 of the total recombination. At the maximum power point, the fundamental recombination fraction can drop to half, as surface and bulk Shockley–Read–Hall step in. As a result, to further increase the performance at the operating point, it is paramount to reduce the bulk dependence and secure proper surface passivation. Bulk recombination can be mitigated either by reducing bulk defect density or by reducing the wafer thickness. We demonstrate that for commercially-viable solar-grade silicon, thinner wafers and surface saturation current densities below 1 fA cm−2, are required to significantly increase the practical efficiency limit of solar cells up to 0.6% absolute. For a high-quality n-type bulk silicon minority-carrier lifetime of 10 ms, the optimum wafer thickness range is 40–60 μm, a very different value from 110 μm previously calculated assuming undoped substrates and solely Auger and radiative recombination. In this thickness range surface saturation current densities near 0.1 fA cm−2 are required to narrow the gap towards the fundamental efficiency limit. We experimentally demonstrate surface saturation currents below 0.5 fA cm−2 on pi/CZ/in structures across different wafer thicknesses (35–170 μm), with potential to reach open-circuit voltages close to 770 mV and bandgap-voltage offsets near 350 mV. Finally, we use the bandgap-voltage offset as a metric to compare the quality of champion experimental solar cells in the literature, for the most commercially-relevant photovoltaic cell absorbers and architectures.