Silicon Heterojunction Research Articles

Self-Diffusion Effect Assisted TiO2/Li3PO4 Electron Selective Passivating Contact in Silicon Solar Cells Approaching 23% Efficiency.

Carrier selective contacts with passivation effects are considered to have a significant influence on the performance of crystalline silicon (c-Si) solar cells. It is essential for electron selective contact materials to meet the requirements of ultra-low contact resistance and excellent passivation effects. This work introduces a stack layer of Lithium Phosphate (Li3PO4) /Titanium Dioxide (TiO2) as a new electron selective passivating contact. It is found that the stack achieves an impressive contact resistivity (ρc) of 0.128mΩcm2 on n-type c-Si substrates with resistivity ranging from 1 to 3Ωcm (14.6mΩcm2 for the n-Si/a-Si:H/Li3PO4/TiO2/Al contact). Furthermore, it effectively reduces the surface recombination parameter (J0) to less than 4fA by incorporating a 6nm a-Si:H(i) layer. The characterization of the n-Si/Li3PO4/TiO2 interface reveals that phosphorus diffusion into silicon plays a crucial role in achieving the ultra-low contact resistivity, while the presence of PO4 3- groups helps in fixing hydrogen atoms to maintain the desired chemical passivation effect. Finally, a silicon heterojunction solar cell (SHJ) with a rear full-area configuration of a-Si:H/Li3PO4/TiO2/Al is successfully demonstrated achieving an impressive power conversion efficiency of 22.89%. The result proves the efficacy of employing hydrogen-rich low-work function metal oxide stacks as electron selective passivating contacts.

Solution-Processed Fabrication of Ni3S2-Based Nanoheterostructure on Silicon Heterojunction Photocathode for Boosting Solar Hydrogen Generation.

Silicon heterojunction (SHJ) solar cell is an advanced and mature photovoltaic cell. Development of photoelectrochemical (PEC) water splitting devices for hydrogen fuel production using SHJ solar cells is considered as a promising approach to address energy crisis. To achieve this goal, it is necessary to deposit passivation layer and cocatalyst layer on the photoelectrode. However, the development of low-cost and scalable preparation methods for high-quality passivation and cocatalyst layer continues to be a significant challenge. Herein, an efficient passivation layer and hydrogen evolution reaction (HER) catalyst are successfully fabricated via solution processed methods. To improve the HER activity of Ni3S2, a Ni3S2-based nanoheterostructure of crystalline Ni3S2, Ni, and amorphous Y(OH)3 is constructed. The optimized photocathode exhibits excellent PEC-HER performance, which achieves a saturated photocurrent of -35.5mA cm-2 and an applied bias photon-to-current efficiency (ABPE) of 8.4 ±0.1% under simulated AM1.5G one-sun illumination and more than 120h of continuous water splitting. This study paves a way for the design and large-scale manufacturing of cost-efficient SHJ photocathode devices.

Highly Transparent Conductive Gallium-Doped Zinc Oxide Thin Films Grown by Reactive Plasma Deposition for Silicon Heterojunction Solar Cells

Highly Transparent Conductive Gallium-Doped Zinc Oxide Thin Films Grown by Reactive Plasma Deposition for Silicon Heterojunction Solar Cells

Using phosphorus doped hydrogenated silicon oxycarbide film as a window layer on the light entrance side of silicon heterojunction solar cells: The role of phase separation on electron transport

Using phosphorus doped hydrogenated silicon oxycarbide film as a window layer on the light entrance side of silicon heterojunction solar cells: The role of phase separation on electron transport

TiO2 and down-conversion phosphors to enhance UV protection of solar cells

In recent years, demand for solar generators for LEO (Low Earth Orbit) applications has been growing, and much research has focused on the use of less expensive and thinner (<90 μm). silicon-based solar cells that can be integrated on flexible Photovoltaic Assemblies (PVAs). These solar cells must be protected from space UV radiations and also withstand more than 50,000 thermal cycles in LEO. The solution advocated here involves the incorporation of UV-absorbing particles into a spatial polymer, combined with lanthanide ions based inorganic phosphors (Y2O3:Eu3+ and Y2O2S:Eu3+) to achieve the down-conversion process. Embedded into a silicone-based polymer matrix with a thickness close to 100 μm, these particles are then deposited on 180 μm thick Ga-doped heterojunction silicon cells (30x30 mm2). UV tests are carried out on ONERA's SEMIRAMIS platform at two doses: 425 esh and 1005 esh. A series of 1000 thermal cycles is carried out at the CEA. The first spatial UV analysis revealed a maximum loss of almost 5 % in short-circuit current (Isc) for PV devices after 1005 esh. Comparing results in open circuit voltage (Voc), the bare cell degrades as the dose increases (−2 % at 425 esh and −5 % at 1005 esh). One positive point is that the addition of TiO2 particles protects the solar cell. These initial results point out that it is possible to produce a protective coating to limit the effects of degradation of Silicon cells under space UV flux, with a focus on producing flexible PVAs.

Metallization process optimization of HIT solar cell for high current density and silver reduction

Metallization process optimization of HIT solar cell for high current density and silver reduction

Downshifting Encapsulant: Optical Simulation Evaluation of the Solution to Ultraviolet‐Induced Degradation in Silicon Heterojunction Solar Cells

Ultraviolet (UV)‐induced degradation (UVID) poses a significant challenge for the prospective mass production of silicon heterojunction (SHJ) solar cells, known for their high efficiency. In this study, the magnified impact of UV radiation when employing a silicon carbide (SiC)‐based transparent passivating contact (TPC) on the front side of SHJ solar cells is reported. A reduction in open‐circuit voltage (VOC), short‐circuit current (JSC), and fill factor of 12%, 6%, and 11%, respectively, is observed after UV exposure. Conventional UVID mitigation measures, UV‐blocking encapsulation, are assessed through single‐cell TPC laminates, revealing an unavoidable tradeoff between current loss and UVID. Alternatively, the utilization of ultraviolet‐downshifting (UV‐DS) encapsulants is proposed to convert UV radiation into the visible light spectrum. An optical simulation method, conducted via OPAL2, is presented to evaluate UV‐DS encapsulants for diminishing UVID in SHJ solar cells with different front contacts. A simple methodology is proposed to mimic the optical property of UV‐DS encapsulants. In the simulation results, additional current gains of up to 0.33 mA cm−2 achievable with suitable UV‐DS encapsulants are highlighted. The factors related to the UV‐DS effects are evaluated and the optimization pathway for UV‐DS encapsulants is elucidated.

Interface properties study of black silicon solar cells with front surface a-Si:H/c-Si heterojunction

Abstract The exceptionally low reflectance of black silicon (Si) across a broad wavelength range makes it an intriguing surface texture for solar cell applications. Si heterojunction (SHJ) solar cells fabricated on black Si formed by dry reactive ion etching using inductive coupled plasma on n-type Si are explored. The study is focused on the properties of the a-Si:H/ crystalline silicon interface, being a key issue for the photovoltaic performance of SHJ. Deep-level transient spectroscopy detected no radiation defect in Si after the etching. The surface of black Si was passivated with an intrinsic a-Si:H layer, followed by the deposition of p-type and n-type a-Si:H on the front and back sides, respectively. The SHJ solar cell photovoltaic performance based on black Si is strongly influenced by defect density at the a-Si:H/Si interface. Admittance spectroscopy and effective charge carrier lifetime measurements demonstrate that interface defect density decreases with the increase of (i) a-Si:H thickness. The value of 0.75 ms effective charge carrier lifetime was reached for single (i) a-Si:H layer passivation and 0.25 ms when (p)a-Si:H was deposited over the intrinsic a-Si:H layer. The measured open circuit voltage values for the SHJ solar cells increase with the (i) a-Si:H layer thickness reaching 658 mV. However, the fill factor decreases with increasing (i) a-Si:H layer thickness, limiting the efficiency at the maximum value below 14% due to the thickness uniformity of the a-Si:H layer. The development of conformal growth of a-Si:H is a key issue for further improvement of black Si heterojunction solar cell photovoltaic performance.

Interpretation of the degradation and trends in the performance of heterojunction silicon solar cells at low temperature

Interpretation of the degradation and trends in the performance of heterojunction silicon solar cells at low temperature

Nanoimprint Lithography for Solar Cell Applications

Nanoimprint lithography (NIL) has emerged as a noteworthy technology in the realm of fabricating micro- and nanostructures with anti-reflective characteristics for diverse solar cell applications. This advanced technique presents a cost-effective approach, accompanied by a vast array of design versatility, thereby facilitating enhanced flexibility in optimizing the efficiency of photovoltaic systems. NIL boasts a multitude of applications across nearly all solar cell types. This article delves into the utilization of NIL and its influence on power conversion efficiency within various solar cell categories, encompassing silicon-based solar cells (including monocrystalline, polycrystalline, amorphous, microcrystalline, and silicon heterojunction solar cells), third-generation solar cells (such as copper indium gallium diselenide, dye-sensitized, perovskite, and organic solar cells), compound solar cells, nanowire-based solar cells, and bio-inspired solar cell structures. By capitalizing on the multiscale textures achievable through the NIL process, substantial advancements can be made in further elevating the performance of solar cells.

Perovskite/Silicon Tandem Solar Cells Above 30% Conversion Efficiency on Submicron-Sized Textured Czochralski-Silicon Bottom Cells with Improved Hole-Transport Layers.

In perovskite/silicon tandem solar cells, the utilization of silicon heterojunction (SHJ) solar cells as bottom cells is one of the most promising concepts. Here, we present optimization strategies for the top cell processing and their integration into SHJ bottom cells based on industrial Czochralski (Cz)-Si wafers of 140 μm thickness. We show that combining the self-assembled monolayer [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with an additional phosphonic acid (PA) with different functional groups, can improve film formation when used as a hole transport layer improving wettability, minimizing shunt fraction and reducing nonradiative losses at the buried interface. Transient surface photovoltage and transient photoluminescence measurements confirm that the combined Me-4PACz/PA layer has similar charge transport properties to Me-4PACz alone. Moreover, this work demonstrates the potential for thin, double-side submicron-sized textured industry-relevant silicon bottom cells yielding a high accumulated short-circuit current density of 40.2 mA/cm2 and reaching a stabilized power conversion efficiency of >30%. This work paves the way toward industry-compatible, highly efficient tandem cells based on a production-compatible SHJ bottom cell.

Resistivity analysis on the enhancement of silicon heterojunction solar cells in light-thermal treatment

Resistivity analysis on the enhancement of silicon heterojunction solar cells in light-thermal treatment

Ultrathin Self-Assembled Monolayer for Effective Silicon Solar Cell Passivation.

Passivation technology is crucial for reducing interface defects and impacting the performance of crystalline silicon (c-Si) solar cells. Concurrently, maintaining a thin passivation layer is essential for ensuring efficient carrier transport. With an ultrathin passivated contact structure, both Silicon Heterojunction (SHJ) cells and Tunnel Oxide Passivated Contact (TOPCon) solar cells achieve an efficiency surpassing 26%. To reduce production costs and simplify solar cell manufacturing processes, the rapid development of organic material passivation technology has emerged. However, its widespread industrial production is hindered by environmental safety concerns, such as strong acid corrosion and biological and ecological safety issues. Here, we discovered a low-cost self-assembled monolayer (SAM) hole-selective transport material known as 2PACz ([2-(9H-carbazol-9-yl) ethyl] phosphonic acid) with phosphate groups to form c-Si solar cells for the first time. The ultrathin film of 2PACz with phosphate groups can establish strong and stable P-O-Si bonds on the silicon surface. Meanwhile, like 2PACz, a uniform ultrathin film with a carbazole function group can offer electron-localizing and thus hole-selective properties, which provides ideas for studying dopant-free silicon solar cells. As a result of such interfacial passivation engineering, it plays an important role in repairing porous structures, such as pyramid-textured silicon surfaces, and cutting losses during the commercialization of c-Si solar cells. Crucially, this advancement offers insights for the development of new high-efficiency ultrathin film passivation methods in the postsilicon era.

Enhancement of optoelectronic properties of Vanadium nitride/porous silicon heterojunction photodetector prepared by electrochemical etching and reactive DC sputtering

Enhancement of optoelectronic properties of Vanadium nitride/porous silicon heterojunction photodetector prepared by electrochemical etching and reactive DC sputtering

Laser‐Sintered Silver Metallization for Silicon Heterojunction Photovoltaic Cells

Herein, a novel metallization technique is reported for crystalline silicon heterojunction (SHJ) solar cells in which silver (Ag) fingers are printed on the SHJ substrates by dispensing Ag nanoparticle‐based inks through a needle and then sintered with a continuous‐wave carbon dioxide (CO2) laser. The impact of the Ag ink viscosity on the line quality and the line resistance is investigated on three Ag inks with different viscosities. Increasing ink viscosity yields higher Ag contact heights, larger aspect ratios, and lower line resistance values. The Ag line height increases from less than a micrometer to ≈18.62 ± 3.48 μm with the increasing viscosity. Photoluminescence imaging shows that the low‐resistance Ag metal contacts obtained do not result in any passivation damage of the SHJ substrate. This is because the wavelength of light emitted from the CO2 laser (i.e., 10.6 μm) leads to optical absorption in the Ag, but this light is effectively transparent to the transparent conductive oxide film, amorphous silicon films, and crystalline silicon substrate. Bulk resistivity values as low as 6.5 μΩ cm are obtained for the laser‐sintered Ag contact and printed using the Ag ink with the highest viscosity in this work.

27.09%-efficiency silicon heterojunction back contact solar cell and going beyond

Crystalline-silicon heterojunction back contact solar cells represent the forefront of photovoltaic technology, but encounter significant challenges in managing charge carrier recombination and transport to achieve high efficiency. In this study, we produced highly efficient heterojunction back contact solar cells with a certified efficiency of 27.09% using a laser patterning technique. Our findings indicate that recombination losses primarily arise from the hole-selective contact region and polarity boundaries. We propose solutions to these issues and establish a clear relationship between contact resistivity, series resistance, and the design of the rear-side pattern. Furthermore, we demonstrate that the wafer edge becomes the main channel for current density loss caused by carrier recombination once electrical shading around the electron-selective contact region is mitigated. With the advanced nanocrystalline passivating contact, wafer edge passivation technologies and meticulous optimization of front anti-reflection coating and rear reflector, achieving efficiencies as high as 27.7% is feasible.

Failure modes of silicon heterojunction photovoltaic modules in damp heat environment: Sodium and moisture effects

Failure modes of silicon heterojunction photovoltaic modules in damp heat environment: Sodium and moisture effects

Silicon heterojunction back-contact solar cells by laser patterning.

Back-contact silicon solar cells, valued for their aesthetic appeal because they have no grid lines on the sunny side, find applications in buildings, vehicles and aircraft and enable self-power generation without compromising appearance1-3. Patterning techniques arrange contacts on the shaded side of the silicon wafer, which offers benefits for light incidence as well. However, the patterning process complicates production and results in power loss. We employed lasers to streamline the fabrication of back-contact solar cells and enhance the power-conversion efficiency. Using this approach, we produced a silicon solar cell that exceeded 27% efficiency. Hydrogenated amorphous silicon layers were deposited onto the wafer for surface passivation and to collect light-generated carriers. A dense passivating contact, which differs from conventional technology practice, was developed. Pulsed picosecond lasers operating at different wavelengths were used to create the back-contact patterns. The approach developed is a streamlined process for producing high-performance back-contact silicon solar cells, with a total effective processing time of about one-third that of the emerging mainstream technology. To meet the terawatt demand, we developed indium-less cells at 26.5% efficiency and precious silver-free cells at 26.2% efficiency. Thus, the integration of solar solutions into buildings and transportation is poised to expand with these technological advances.

Improved electrical contact properties in Indium-free silicon heterojunction solar cells with amorphous SnO2 TCO layers

Improved electrical contact properties in Indium-free silicon heterojunction solar cells with amorphous SnO2 TCO layers

Investigation of Graphene Single Layer on P-Type and N-Type Silicon Heterojunction Photodetectors.

Photodetectors are of great interest in several technological applications thanks to their capability to convert an optical signal into an electrical one through light-matter interactions. In particular, broadband photodetectors based on graphene/silicon heterojunctions could be useful in multiple applications due to their compelling performances. Here, we present a 2D photodiode heterojunction based on a graphene single layer deposited on p-type and n-type Silicon substrates. We report on the electro-optical properties of the device that have been measured in dark and light conditions in a spectral range from 400 nm to 800 nm. The comparison of the device's performance in terms of responsivity and rectification ratio is presented. Raman spectroscopy provides information on the graphene single layer's quality and oxidation. The results showcase the importance of the doping of the silicon substrate to realize an efficient heterojunction that improves the photoresponse, reducing the dark current.