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Doped hydrogenated nanocrystalline silicon oxide layers for higha??efficiency ca??Si heterojunction solar cells
摘要： 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.
关键词： silicon heterojunction (SHJ),carrier-selective-contacts (CSCs),interface treatments,optoelectrical properties,hydrogenated nanocrystalline silicon oxide (nc-SiOx:H)
更新于2025-09-23 15:19:57
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Investigation of anomalous behaviour in J-V and Suns-Voc characteristics of carrier-selective contact silicon solar cells
摘要： Process and configuration dependent carrier-selective Ag/ITO/MoOx/n-Si/LiFx/Al silicon solar cells having conversion efficiencies from 6.5% to 14.5% are investigated. Some of the cells’ anomalous characteristics in light J-V and Suns-VOC graphs are analysed by photo-induced capacitance-voltage (C-V), impedance spectroscopy (IS), and voltage- plus light-biased (white, blue and infrared) quantum efficiency (QE). Correlated analysis of cells revealed the physical origin of S-shape in light J-V and turnaround in Suns-VOC graphs. After air exposure of the MoOx film, the charge carrier accumulation at the front interface and inefficient transport through the MoOx layer have led to the anomalous features in light J-V and Suns-VOC graphs of the cell. This is reflected as an additional peak and arc in C-V and IS graphs, respectively. In the absence of the LiFx layer, the cell has shown the only turnaround in Suns-VOC graph due to the Schottky barrier. The IS analysis resolved carrier transport issues at the front junction and back contact of the cells with a distinguished response. The light-bias dependent QE analysis has confirmed the presence of carrier collection barrier at the MoOx/c-Si interface, and the Schottky contact at the back with a different response in EQE spectra.
关键词： Silicon,Turnaround,S-shape,Heterojunction,Molybdenum oxide,Solar cells,Lithium Fluoride,Carrier-selective contacts
更新于2025-09-19 17:13:59
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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Evaluation of localized vertical current formation in carrier selective passivation layers of silicon solar cells by conductive AFM
摘要： Carrier selective contacts are of growing interest in the development and optimization of high efficiency silicon solar cell concepts. In particular, the passivation mechanism of ultra-thin oxide layers in interaction with poly-Si layers came into focus and the origin of tunnel currents and the so called pinhole conductivity is discussed. Many process parameters and their influence on the passivation effect are not clear, yet. The present study investigates the electrical properties in Si/SiOx/poly-Si layer system from different processes. For this purpose, high-resolution electrical evaluation of the current path density through the interfacial oxide is investigated by conductive AFM using a newly developed image calculation software tool to determine the vertical current path density. We compared two thicknesses of poly-Si (n+ PECVD) layers each at optimum annealing temperature (corresponding to highest i-VOC). The influence of three annealing temperatures (at optimum passivation, below and above) is investigated for an ozone oxide and pinhole densities are analyzed by the TMAH method. Finally, the optimum properties of the layer stack for three interfacial oxides (each at optimum passivation) are studied.
关键词： silicon solar cells,pinhole conductivity,passivation layers,carrier selective contacts,conductive AFM
更新于2025-09-16 10:30:52
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Origin of the tunable carrier selectivity of atomic-layer-deposited TiOx nanolayers in crystalline silicon solar cells
摘要： Titanium oxide (TiOx) nanolayers grown by atomic layer deposition are investigated with respect to their application as carrier selective contacts for crystalline silicon (c-Si) solar cells. Although TiOx is known to act as an electron contact, in this work the selectivity of TiOx layers is found to be widely tunable from electron to hole selective depending on deposition conditions, post-deposition treatments, and work function of the metal electrode used. Using TiOx and an intrinsic hydrogenated amorphous silicon buffer layer, solar cell test structure exhibiting open-circuit voltages (Voc) as high as 720 and 650 mV are shown for electron and hole selective contacts, respectively. Surface photovoltage and capacitance-voltage measurements reveal that carrier selectivity is correlated with the amount of c-Si band bending induced by TiOx, which are governed not only by the effective work function difference at the Si/TiOx interface, but also by the negative fixed charge present in the TiOx layer. This new finding is in contrast to the previous model for carrier transport where selectivity is determined only by the asymmetric band offsets at the Si/contact interface. It highlights the influence of induced band bending to produce carrier depletion/inversion conditions, and the importance of its selectivity effect in a c-Si absorber.
关键词： Titanium oxide,Solar cells,Carrier selective contacts,Atomic layer deposition
更新于2025-09-16 10:30:52
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Hard mask processing of 20% efficiency back-contacted silicon solar cells with dopant-free heterojunctions
摘要： Single junction crystalline silicon (c-Si) solar cells featuring a conventionally doped interdigitated back contact heterojunction (IBC-SHJ) structure has approached a record efficiency of 26.6%, which is very close to the practical limit. However, integrating the interdigital p- and n-type amorphous silicon (a-Si:H) layers on the rear surface of Si substrate is of such complexity, posing problem of heavy dependences on expensive manufacturing techniques including plasma-enhanced chemical vapor deposition and photolithography. Its commercial potential is thus always being questioned, and to seek an alternative fabrication procedure, which adapts to cost-effective deposition parallel with simple patterning characteristics, has been a primary research target of related subjects. Here, we demonstrated 20.1% efficiency dopant-free IBC-SHJ solar cells by combining evaporated carrier-selective materials (MoOx and LiFx) and two-steps hard masks alignments, delivering substantial simplifications in the architecture and fabrication procedures. We investigated the effect of intrinsic a-Si:H films with different thicknesses on the passivation and contact resistance for both a-Si:H/MoOx and a-Si:H/LiFx contacts, showing 4 nm a-Si:H is better for high efficiency IBC-SHJ solar cells. We also found that the position of the metal target (electrode definition step) and isolation in between the busbar and the Si substrate are highly relevant to leakage and recombination and have great impact on the device performance. The dopant-free IBC-SHJ solar cells demonstrated here manifest enough confidence in our hard mask based fabrication procedure, with great potential for high performance-to-cost ratio in future.
关键词： solar cells,dopant-free,interdigitated back contact,silicon,carrier-selective,contacts,heterojunction
更新于2025-09-12 10:27:22
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Mitigating Plasmonic Absorption Losses at Rear Electrodes in High‐Efficiency Silicon Solar Cells Using Dopant‐Free Contact Stacks
摘要： Although charge-carrier selectivity in conventional crystalline silicon (c-Si) solar cells is usually realized by doping Si, the presence of dopants imposes inherent performance limitations due to parasitic absorption and carrier recombination. The development of alternative carrier-selective contacts, using non-Si electron and hole transport layers, has the potential to overcome such drawbacks and simultaneously reduce the cost and/or simplify the fabrication process of c-Si solar cells. Nevertheless, devices relying on such non-Si contacts with power conversion efficiencies (PCEs) that rival their classical counterparts are yet to be demonstrated. In this study, one key element is brought forward toward this demonstration by incorporating low-pressure chemical vapor deposited ZnO as the electron transport layer in c-Si solar cells. Placed at the rear of the device, it is found that rather thick (75 nm) ZnO film capped with LiFx/Al simultaneously enables efficient electron selectivity and suppression of parasitic infrared absorption. Next, these electron-selective contacts are integrated in c-Si solar cells with MoOx-based hole-collecting contacts at the device front to realize full-area dopant-free-contact solar cells. In the proof-of-concept device, a PCE as high as 21.4% is demonstrated, which is a record for this novel device class and is at the level of conventional industrial solar cells.
关键词： ZnO,plasmonic absorption,c-Si solar cells,carrier-selective contacts,dopant-free contacts
更新于2025-09-11 14:15:04
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Temperature-dependent interface stability of MoO <sub/>3</sub> /GaAs(001) hybrid structures
摘要： We report on the influence of growth temperature and post-growth annealing on interface formation and film structure of thin MoO3 films on GaAs(001), which plays an important role for a future application as carrier-selective contacts or diffusion barriers in III/V-semiconductor spin- and opto-electronics or photovoltaics. Growth and post-growth annealing were performed in a manner that emulates heterostructure growth and lithographic processing. High-resolution transmission electron microscopy reveals nanocrystalline (“amorphous”) growth at temperatures up to 200 °C and a transition to polycrystalline growth at about 400 °C. Spatially resolved chemical analysis by energy dispersive x-ray spectroscopy reveals strong intermixing at the MoO3/GaAs(001) interface proceeding during both film deposition and annealing. Our results evidence the important role of intermixing occurring during the process of interface formation at the very beginning of deposition.
关键词： intermixing,temperature-dependent,interface stability,GaAs(001),diffusion barriers,MoO3,carrier-selective contacts
更新于2025-09-10 09:29:36