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Performance analysis of c-Si heterojunction solar cell with passivated transition metal oxides carrier-selective contacts
摘要： Transition metal oxides (TMOs) as passivating carrier-selective contact layers are investigated for silicon heterojunction solar cells. MoOx as hole-selective layer and TiOx as an electron-selective layer are explored in detail to design a high-efficiency silicon heterojunction solar cell without any specified surface passivation layer. The thickness and optical transparency of the MoOx hole-selective layer have been evaluated through optical simulation. The impact of TMOs’ work function and their passivation quality has been examined in detail to extract the maximum conversion efficiency from silicon heterojunction solar cells. To increase the optical absorption in c-Si, the micro–nanopillar structure has also been implemented. It has been found that the barrier height at the TMO/silicon heterocontact plays a significant role in the overall performance improvement of the solar cell. The optimized cell design without doping and separate passivating layer can achieve a power conversion efficiency of ~ 22%. Our findings open the potential pathways and opportunities to obtain simplified heterojunction solar cells at lower temperatures and without impurity doping.
关键词： Surface recombination velocity,Carrier-selective contact layers,Transition metal oxides,c-Si heterojunction solar cells
更新于2025-09-23 15:21:01
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Properties of Thermally Evaporated Titanium Dioxide as an Electron-Selective Contact for Silicon Solar Cells
摘要： Recently, titanium oxide has been widely investigated as a carrier-selective contact material for silicon solar cells. Herein, titanium oxide ?lms were fabricated via simple deposition methods involving thermal eVaporation and oxidation. This study focuses on characterizing an /TiO2 electron-selective passivated contact layer with this oxidized method. Subsequently, the SiO2 stack was examined using high-resolution transmission electron microscopy. The phase and chemical composition of the titanium oxide ?lms were analyzed using X-ray di?raction and X-ray photoelectron spectroscopy, respectively. The passivation quality of each layer was con?rmed by measuring the carrier lifetime using quasi-steady-state photoconductance, providing an implied open circuit voltage of 644 mV. UV–vis spectroscopy and UV photoelectron spectroscopy analyses demonstrated the band alignment and carrier selectivity of the TiO2 layers. Band o?sets of ~0.33 and ~2.6 eV relative to the conduction and valence bands, respectively, were con?rmed for titanium oxide and the silicon interface.
关键词： carrier-selective contact cell,band alignment,titanium oxide,electron-selective contact
更新于2025-09-23 15:19:57
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Low Work Function Ytterbium Silicide Contact for Doping-Free Silicon Solar Cells
摘要： Metal silicide is a well-known material for contact layers, however, it has not been tested in the context of doping-free carrier selective contacts. Thin film deposition of an appropriate metal with mild annealing treatment is an interesting alternative to the more complex depositions of other compound materials. Reaction of Yb deposited on top an i-a-Si:H passivation layer results in the formation of YbSix on top of a remnant i-a-Si:H following a low-temperature anneal below 200 °C. Such a contact is an interesting candidate as a doping-free electron-selective contact. Detailed investigation of the i-a-Si/YbSix contact shows that Yb thickness, i-a-Si:H thickness and silicidation annealing conditions play a significant role in determining the recombination current density (J0,metal) and the contact resistivity (ρc). Low J0,metal of 5 fA/cm2 and low ρc below 0.1 ?.cm were independently demonstrated for such i-a-Si:H/YbSix contacts. We also demonstrate that low-temperature silicidation can be combined with contact sintering (160 °C/25 min) or module lamination (160 °C/20 min), which are potential pathways for process simplification. Combining the optimised i-a-Si:H/YbSix electron contact with MoOx based hole contact in the MolYSili doping-free cell (i-a-Si:H/MoOx+ i-a-Si:H/YbSix), we achieved 16.7 % in average efficiency and 17.0 % for the champion cell. Furthermore, the YbSix contact stability was evaluated at module level and excellent thermal stability of the MolYSili laminate was demonstrated using the damp-heat test method (humidity 85 %, 85 °C, 1000 h), where the laminated MolYSili cell did not show any degradation in the cell efficiency. This is the first proof-of-concept demonstration of a stable silicide-based contact for low-temperature processed doping-free solar cells.
关键词： Yb silicide,electron-selective contact,passivating contact,doping-free cells,pinning
更新于2025-09-23 15:19:57
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Polymeric Electron-Selective Contact for Crystalline Silicon Solar Cells with an Efficiency Exceeding 19%
摘要： Carrier-selective contacts have become a prominent path forward towards efficient crystalline silicon (c-Si) photovoltaics. Among the proposed contacting materials, organic materials may offer simplified and low-cost processing compared with typical vacuum deposition techniques. Here, branched polyethyleneimine (b-PEI) is presented as an electron-transport layer (ETL) for c-Si solar cells. The incorporation of b-PEI interlayer between c-Si(n) and Al leads to a low contact resistivity of 24 mΩ cm2. Silicon heterojunction solar cell integrated with b-PEI is demonstrated achieving a power conversion efficiency of 19.4%, which improves the benchmark efficiency of a c-Si solar cell with an organic ETL. This electron-selectivity of b-PEI is attributed to its Lewis basicity, i.e., electron donating ability, promoting favorable band bending at the c-Si surface for electron transport. Moreover, several other Lewis base polymers perform as efficient ETLs in organic/c-Si hybrid devices, indicating Lewis basicity could be a guideline for future organic ETLs design.
关键词： solar cells,crystalline silicon,polymeric electron-selective contact,b-PEI,Lewis basicity
更新于2025-09-23 15:19:57
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Elucidating Charge Separation in Particulate Photocatalysts Using Nearly-Intrinsic Semiconductors with Small Asymmetric Band Bending
摘要： Photocatalytic water splitting using particulate suspensions is a promising approach for achieving large-scale production of renewable hydrogen fuels. Previous studies have hypothesized that band energy levels of such photocatalysts in water are both flat and symmetrical, and the charge separation in such photocatalysts is driven by random charge carrier diffusion. However, it is not well understood how the observed asymmetry of carrier diffusion is achieved during photocatalysis. To fully understand this charge separation process, we used double-side polished, intrinsic silicon as a model light absorber and manipulated the direction of charge-carrier diffusion using combinations of carrier-selective contacts. Degenerately p-type doped and n-type doped silicon, along with as-grown and annealed TiO2 overlayers grown by atomic layer deposition, were used as carrier selective back and front contacts, respectively. The protective TiO2 layers along with nickel oxide co-catalysts enabled bi-functional, stable silicon photoelectrodes for photoelectrochemical hydrogen evolution and water oxidation in alkaline solution. A device simulation was applied to analyse the experimental results and further gain understandings on the charge separation process in photocatalysts involving semiconductor/liquid junctions. Combined experimental and simulation study indicated that the contacts established asymmetric band bending inside the intrinsic silicon layer and drove the directional charge separation, primarily carrier diffusion. By scaling down the thickness of the silicon layer in the simulation, analogies of charge separation in particulate photocatalysts can be drawn. Based on the understandings from intrinsic silicon, we further revealed that photocatalysts generally do require asymmetric band bending to drive diffusional charge separation, and that a small band edge offset of 0.45 eV between reductive and oxidative catalytic sites can build a sufficient, steady-state photovoltage of over 1.23 V for overall water splitting by using a model SrTiO3 absorber. It provides an insightful guidance for designing efficient and stable particulate photocatalysts especially those using Si and III-V semiconductors with protective layers such as TiO2.
关键词： Carrier-selective contact,Particulate photocatalyst,Charge separation
更新于2025-09-19 17:15:36
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Effects of oxidation state on photovoltaic properties of reactively magnetron sputtered hole-selective WO<sub>x</sub> contacts in silicon heterojunction solar cells
摘要： The stoichiometry value x of WOx, or its oxidation state, is crucial for improving performances of the hole-selective contact heterojunction silicon solar cell. However, it is challenging to tune the films’ oxidation state using the well-known evaporation method. In this study, a simulation was performed to analyze the effect of x on short-circuit current (Jsc) loss, attributed to the hole-selective contact in the device. Compared to the thickness of WOx layer, x has a more important role in minimizing Jsc loss. Based on the simulation, the WOx/c-Si heterojunction solar cells having hole-selective WOx contacts with tuned x to vary its oxidation state were fabricated using reactive magnetron sputtering. The relationships of the open-circuit voltage (Voc) and Jsc with respect to x were similar. The experimentally determined Jsc increased from 34.7 to 36.6 mA/cm2 when x was increased from 2.72 to 2.77; this result is consistent with the simulation. Nevertheless, fill factor (FF) reduced with the increase of x, owing to the reduced conductivity of WOx. Both oxidation state and film conductivity must be as high as possible to simultaneously achieve high Voc, Jsc, and FF. The lowest x yielded a solar cell efficiency of 13.3%.
关键词： Current loss,Tungsten oxide,Hole-selective contact,Heterojunction solar cell
更新于2025-09-19 17:13:59
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Interfacial engineering to boost photoresponse performance and stability of V2O5/n-Si heterojunction photodetectors
摘要： Transitional metal oxides (TMOs) have demonstrated as a promising alternative to doped layers in high-efficient crystalline silicon heterojunction solar cells. However, the unintentional oxidation causes serious carrier recombination at the interface, which accounts for the low photoelectric conversion efficiency and poor stability. Herein, a self-powered, broad-band, fast-response V2O5/n-Si heterojunction photodetectors (PDs) are fabricated by thermal evaporation of an ultrathin V2O5 thin films on nanoporous pyramid silicon structures. By interfacial engineering with structural optimization and surface methyl passivation, the photodetection performance and stability of V2O5/n-Si PDs can be significantly enhanced. The V2O5/n-Si heterojunction PDs demonstrate a high on/off ratio of 1.4×104, fast-response speed of 9.5 μs, high responsivity of 185 mA·W-1 (@940 nm) and high specific detectivity (1.34×1012 Jones). Based on the energy band alignment analysis, the excellent photoresponse performance is mainly attributed to the efficient carrier separation after surface passivation by methyl group. Additionally, the built-in electric field at the interface also accelerates the charge carrier separation. Our work would contribute to the fabrications of other TMOs-based heterojunctions, and give some enlightening insights into the understanding of carrier transportation in heterojunctions.
关键词： Carrier selective contact,Heterojunction photodetectors,Transition metal oxides,Interface engineering
更新于2025-09-16 10:30:52
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Optimization of SnO2-based electron-selective contacts for Si/PEDOT:PSS heterojunction solar cells
摘要： Tin oxide (SnO2) is a potentially excellent electron-selective contact (ESC) for silicon (Si)-based solar cells due to its satisfactory energy band structure and good crystallinity. However, unsatisfactory electron extraction ability and limited surface passivating effect of SnO2 ESCs will limit the performance of corresponding solar cells. We increase the Fermi level of SnO2 by doping Ethylene diamine tetraacetic acid (EDTA), which endows EDTA-SnO2 better electron extraction ability than SnO2. Moreover, EDTA-SnO2/SiOx bilayer ESC prepared by combining a EDTA-SnO2 layer and a thin silicon oxide (SiOx) film provides better surface passivation than EDTA-SnO2 ESC without impairing the charge transport capability markedly. The planar Si/PEDOT:PSS heterojunction solar cells (HSCs) with EDTA-SnO2/SiOx bilayer ESCs exhibit a power conversion efficiency (η) of 11.52%, which improves 13.7% in comparison with the η (10.13%) of HSCs with SnO2 ESCs, mainly caused by the increase in Voc and FF by 18 mV and 5.4% respectively.
关键词： Tin oxide,Electron-selective contact,Surface passivation,Silicon heterojunction solar cells,Fermi level
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Photon Management for Silicon Solar Cells featuring Hole-Selective Molybdenum Oxide Rear Contacts: An Optical Simulation Study
摘要： Passivated, hole-selective contacts play important role in reducing surface recombination by lowering the concentration of electrons in the rear side of a solar cell. However, parasitic optical losses in these contacts can still limit the performance of the cell. In this work, the long wavelength optical losses of silicon solar cells featuring hole-selective molybdenum oxide (MoOx) rear contacts are investigated using optical simulations. The potential of these selective contacts for possible enhancement of photogenerated current density was also investigated for their use with nanostructured dielectric layers.
关键词： photon management,FDTD simulation,grating nanostructure,silicon solar cell,hole selective contact
更新于2025-09-16 10:30:52
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Antimony doped tin oxide/polyethylenimine electron selective contact for reliable and light soaking-free high performance inverted organic solar cells
摘要： We have demonstrated a high-performance low temperature solution processed electron selective contact consisting of 10 at. % antimony doped tin oxide (ATO) and the neutral polymer polyethylenimine (PEI). Inverted organic photovoltaics (OPVs) utilizing ATO/PEI as electron selective contact exhibited high power conversion efficiencies for both the reference P3HT:PCBM and the nonfullerene based P3HT:IDTBR active layer OPV material systems. Importantly, it is shown that the proposed ATO/PEI carrier selective contact provides light soaking-free inverted OPVs. Furthermore, by increasing the thickness of the ATO layer from 40 to 120 nm, the power conversion efficiency of the corresponding inverted OPVs remain unaffected, a parameter which indicates the potential of the proposed ATO/PEI carrier selective contact for high performance light-soaking-free and reliable roll-to-roll printing solutions processed inverted OPVs.
关键词： inverted organic solar cells,antimony doped tin oxide,polyethylenimine,light soaking-free,electron selective contact
更新于2025-09-12 10:27:22