Silicon Solar Cell Applications Research Articles

Broadband Sensitized Near‐Infrared Quantum Cutting Materials for Silicon Solar Cells: Progress, Challenges, and Perspectives

Silicon solar cells are currently the most widely used type, accounting for more than 90% of the commercial market. However, the spectral mismatch between the solar spectrum and the absorption spectra of the cells is the main cause restricting their conversion efficiency, which cannot exceed the Shockley–Queisser limit. Quantum cutting can convert one high‐energy photon into two or more low‐energy photons and reduce the energy loss of the high‐energy photons, providing a way to improve the photoelectric conversion efficiency (PCE) of silicon solar cells. The unique electronic configuration of rare‐earth elements gives them excellent optical properties and makes them good candidates for the luminescent centers of quantum cutting materials. This article reviews their luminescence mechanism, energy transfer (ET) mechanism, and application in silicon solar cells and outlines the potential problems of broadband‐sensitized near‐infrared (NIR) quantum cutting materials. Some key issues and future directions are also discussed.

Modelling and analysis of high efficiency silicon solar cell using double layers anti-reflection coatings (ARC)

The modernization that is currently taking over across the world is resulting in numerous advancements in a variety of industries, and the most notable and apparent development is the rising use of solar energy, which has become more prevalent every day. Most companies, residences, schools, and other organizations rely mostly on solar energy as the main source of electricity. It was discovered that anti-reflective coating (ARC) had been applied to solar cells with the goal of increasing power conversion efficiency, decreasing reflection loss, and improving absorption. Although a single layer of ARC is sufficient, applying an additional layer might improve the solar cell application’s effectiveness. Hence, the modeling and analysis of double layers of anti-reflection coating (ARC) with different types of materials have been investigated and evaluated using personal computer one-dimensional (PC1D) simulation software. In this study, the double-layer anti-reflection coating on the solar cell was modeled using PC1D, where this software allowed for one-dimensional simulation of the parameters required for the operation of semiconductor-based solar energy systems. The PC1D simulation reveals that SiO2/TiO2 has the highest efficiency (22.82%) and lowest reflection compared to Si3N4/TiO2 and ZnO/TiO2. Also, SiO2/TiO2 generates the highest external quantum efficiency (EQE) among ARC double layers, making it ideal for silicon solar cell applications in order to boost the solar cell’s efficiency. The results for the effects of current, voltage, reflection, and EQE of the different double layers of ARC have also been studied in this paper.

Novel Interlayer Boosting the Performance of Evaporated Cu2O Hole‐Selective Contacts in Si Solar Cells

Passivating contacts based on transition metal oxides are of great interest for applications in crystalline silicon (c‐Si) solar cells due to their improved optical transparency and potential cost reduction. In this work, the contact resistivity and passivation for thermally evaporated Cu2O are investigated and optimized, with and without an Al2O3 interlayer, as a hole‐selective contact to c‐Si. Additionally, we implement an Al y TiO x /TiO2 stack as a novel passivating tunnel interlayer for hole‐selective contacts, achieving an implied open‐circuit voltage iV oc of 630 mV and a record‐low J 0 of 212 fA cm−2 while maintaining a contact resistivity ρ c of 62 mΩ cm2. A record‐low ρ c of 8 mΩ cm2 for Cu2O‐based contacts is also demonstrated at the expense of passivation. The addition of the interlayer resulted in a 2% absolute improvement in the efficiency of proof‐of‐concept c‐Si cells with full‐area rear Cu2O contacts, reaching 19.1%.The demonstration of this novel interlayer stack provides new avenues to improve the performance also of other hole‐selective passivating contacts.

The Effects of Porous Silicon and Silicon Nitride Treatments on the Electronic Qualities of Multicrystalline Silicon for Solar Cell Applications

The Effects of Porous Silicon and Silicon Nitride Treatments on the Electronic Qualities of Multicrystalline Silicon for Solar Cell Applications

Investigation of the role of Saw damage in Silver catalyzed Metal Assisted Chemical Etching on Multicrystalline Silicon for Solar cell Application

Investigation of the role of Saw damage in Silver catalyzed Metal Assisted Chemical Etching on Multicrystalline Silicon for Solar cell Application

Detailed investigation of electrical and optical properties of textured n-type and roughened p-type tunnel oxide passivated contacts for screen-printed double-side passivated contact silicon solar cell application

This paper presents detailed characterization and analyses of the optical, electrical, and contact properties of a 35 nm phosphorus-doped (n-type) polysilicon (poly-Si) and a 250 nm boron-doped (p-type) poly-Si deposited respectively on textured and roughed surface. These layers could be applied respectively to the front and rear sides of an n-type Si to produce back junction bifacial screen-printed double-side tunnel oxide passivated contacts (DS-TOPCon) solar cells. Optical and device modeling revealed a short circuit current density loss of 1.5 mA/cm2 and 0.5 mA/cm2 due to absorption in the front n-TOPCon and rear side p-TOPCon layers, respectively. The passivation and contact properties including metalized and unmetallized recombination current density (J0), as well as contact resistivity, were determined as a function of contact firing temperature in the range of 700∼800℃. The passivation quality of the front thin n-TOPCon was found to deteriorate with increased firing temperature while the rear thick p-TOPCon improved. The study showed that the simulated contact firing at 730℃ resulted in the best unmetallized double-side TOPCon precursor, with an excellent implied open-circuit voltage of 730 mV and implied fill factor of ∼86 %. However, the metalized J0 increased and contact resistivity decreased monotonically with the increase in the firing temperature. The 2D device simulations revealed that these layers can produce screen-printed DS-TOPCon cells with an efficiency of ∼22.5 %. Solar cell modeling also showed that the DS-TOPCon solar cell efficiency can reach 24.1 % by decreasing the n-TOPCon thickness to 20 nm and lowering the full area metalized J0 to ∼100 mA/cm2.

One step coating anti-reflective SiO2 film for silicon solar cells applications by atmospheric pressure plasma jet

By utilizing an atmospheric pressure plasma jet, a one-step deposition of anti-reflective silicon dioxide coating was successfully achieved on solar cover glass. A two-dimensional moving platform was utilized to coat large-area cover glass measuring 300 mm * 300 mm. Remarkably, at an input power of 40 W, the temperature of the cover glass remained as low as 59.4 °C. The impact of different motion patterns on the anti-reflective properties of the film was thoroughly investigated. Upon assembling the solar cells, a notable efficiency enhancement from 24.03% to 24.28% was observed. This method demonstrates promising prospects for repairing anti-reflective films on malfunctioning solar cell modules in photovoltaic power plants.

Charge trapping and photovoltaic characteristics in monocrystalline silicon solar cells employing molybdenum oxide and copper oxide stacked hole-selective contacts

A hole-selective contact (HSC) composed of stacked layers of molybdenum oxide (MoOx) and copper oxide (CuOx), called MOCOSL, has been proposed as passivation booster for screen-printed monocrystalline silicon solar cell (SMSC) applications. The passivation quality of MOCOSL is investigated by characterizing its charge trapping properties, including fixed oxide charge (Qf) and interface trap density (Dit). The conversion efficiency (CE) of SMSCs is improved by MOCOSL, resulting in an increase from 20.66% to 21.76%. This improvement is attributed to an increase in the negative Qf and a decrease in Dit, which result in an increase in the open circuit voltage (Voc) and short circuit current (Jsc). Specifically, the number of negative Qf is increased by MOCOSL, which helps to reduce the recombination of charge carriers.

Review of Laser Doping and its Applications in Silicon Solar Cells

Laser-doped selective emitter diffusion techniques have become mainstream in solar cell manufacture covering 60% of the market share in 2022 and are expected to continue to grow to above 90% within the next five years (ITRPV). This was a very rapid uptake of technology, coming from only ∼10% penetration in 2018, and has enabled over 20 fA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> front recombination current reductions on the dominant passivated emitter and rear cell concepts in the same short period. In this article, a broad overview of key concepts in relation to laser doping methods relevant to solar cell manufacturing is given. We first discuss the basic mechanisms behind laser doping along with the benefits over conventional doping methods. The main laser doping approaches reported in the literature are then discussed, along with implications for metallization strategy, particularly in relation to selective emitter and back surface field formation in the dominant passivated emitter and rear cell technology. Different cell concepts that have benefited from the application of laser doping are also discussed. In the last section, we discuss the main defects induced by laser processing of silicon which affect the finished devices, potential and debated causes, as well as some commonly applied treatments for their mitigation.

Development of Phosphorus-Doped Nanoscale Poly-Si Passivating Contacts via Inkjet Printing for Application in Silicon Solar Cells

Herein, high-quality localized phosphorus-doped polycrystalline silicon (poly-Si) passivating contacts containing nanoscale poly-Si film (∼100 nm) on an ultrathin SiOx layer (∼1.5 nm) were fabricated via an inkjet printing technique. A detailed study of the impacts of inkjet printer settings, dopant concentration, and annealing temperature on the poly-Si passivating contact performance (represented by implied open-circuit voltage iVoc and contact resistivity ρc) was carried out. By applying optimized process conditions on symmetrical industrially processed intrinsic poly-Si/SiOx/n-type crystalline Si (c-Si) substrates, good surface passivation was achieved with an iVoc of 699 mV, together with a low ρc of 6.4 mΩ·cm2, after annealing at 975 °C. After a hydrogenation treatment via the deposition of aluminum oxide (AlOx)/silicon nitride (SiNy) stack and subsequent forming gas annealing (FGA), the optimum annealing temperature shifted to 950 °C and the iVoc was further improved to an excellent value of 729 mV. Optical images reveal that a line width of 75 μm can be realized on a mechanically polished silicon wafer. Moreover, high-resolution micro-photoluminescence (μ-PL) maps clearly demonstrate the localization of the doped regions on the symmetrical substrate after annealing. These results show that inkjet printing is a promising technique for the fabrication of localized poly-Si/SiOx passivating contacts in high-efficiency solar cells with high flexibility and simplicity.

Photovoltaic and interface characteristics of mono-crystalline silicon solar cells with molybdenum oxide hole-selective layers by ammonium hydroxide reconstructed nanostructure

Ammonium hydroxide reconstructed nanostructure (AHRN) is proposed as an attachment enhancer between molybdenum oxide (MoOx) hole-selective layers (HSLs) and silicon interface for screen-printed mono-crystalline silicon solar cell (SMSC) applications. The conversion efficiency (CE) is demonstrated from 20.6% to 21.6% for SMSCs with MoO2 HSL and attachment enhancer. The betterment mechanism is attributed to a suitable nanostructure, resulting in the increase of the fill factor and peeling force. Moreover, the interface trap density (Dit) is hardly degraded by MoO2 formed on the Si surface at a specific AHRN.

Green upconversion improvement of TiO2 codoped Er3+-Yb3+ nanoparticles based thin film by adding ALD-Al2O3 for silicon solar cell applications

This paper investigates the upconversion luminescence modification of codoped nanoparticles with lanthanides ions based thin films through adding a coating. First, these nanoparticles based thin films composed of Er3+-Yb3+ co-doped anatase-TiO2 are prepared using spin coating technique supported by a design of experiment (DOE) approach with the Hadamard matrix of order 4 to improve the deposition conditions. For the coating step, different thicknesses of Al2O3 layer are realised by thermal atomic layer deposition (T-ALD) onto the surface of Er3+-Yb3+ co-doped anatase-TiO2 nanoparticles based thin films. The results show that the ALD-Al2O3 coating can benefit the luminescence properties of the upconversion nanoparticles based thin films. Thin ALD-Al2O3 (10 nm) coated stack exhibits similar upconversion luminescence as the uncoated nanoparticles based film but insures also their stability. Meanwhile, for 100 nm ALD-Al2O3 coating, enhancement of the upconversion green emission by 98% at the expense of the red emission compared to uncoated sample is observed. This results are promising to be applied in photovoltaics field.

Performance Enhancement of Crystal Silicon Solar Cell by a CsPbBr3–Cs4PbBr6 Perovskite Quantum Dot @ZnO/Ethylene Vinyl Acetate Copolymer Downshifting Composite Film

Crystal silicon solar cells being the most successful photovoltaic devices have prevailed in the energy market for decades. To further improve the device performance, photon management is necessary. Herein, a CsPbBr3–Cs4PbBr6 perovskite quantum dot@ZnO/ethylene vinyl acetate copolymer downshifting composite film is coated on the silicon solar cell. This downshifting composite film helps to convert high‐energy (UV‐blue) photons to relatively low‐energy photons with a wavelength at about 500 nm, which possess higher sensitivity in silicon solar cells. The effects of tetra‐n‐heptylammonium bromide and Zn(C2H5)2 on composition, optical and luminescence properties of perovskite quantum dots are thoroughly investigated, and a clean quantum dot solution with strong luminescent intensity can be obtained. The perovskite quantum dot@ZnO/ethylene vinyl acetate composite film absolutely improves the efficiency of silicon solar cells by 1.18%. The value is much higher than pure ethylene vinyl acetate (0.42%) and composite film without ZnO (0.57%). Moreover, ZnO inclusion can inhibit Cs and Pb leakage and maintain the device working stability, which is helpful for their commercial application in the future. This study further reveals that the enhancement lies in carrier relaxation energy loss reduction. Herein, a low‐cost downshifting composite film with excellent environmental stability for silicon solar cells applications is proposed.

Comparison of C-, N-, and O-Incorporated Non-blistering PECVD Si Films for Application in SiOx-Based Passivating Contacts for Si Solar Cells

For application in high-efficiency silicon solar cells bearing SiOx-based passivating contacts, we have developed 100 nm thick, PECVD Si-rich amorphous films, capable of being processed in industrial furnaces without blistering, by incorporating adequate amounts of each of C, N, and O in the films during PECVD. We found that non-blistering of the films is a result of the low intrinsic stress (compressive) in the films and not due to a low H content, which, in fact, is much higher in the non-blistering films than in the C-, N-, and O-free films. Among the three types of non-blistering Si-rich amorphous films, we conclude that the O-incorporated one is the most suitable for application in SiOx-based passivating contacts owing to the film’s high excess Si content and ability to crystallize.

Luminescence properties and energy transfer of the near-infrared phosphor Ca3In2Ge3O12:Cr3+,Nd3.

The double doping strategy based on energy transfer is an effective way to regulate the NIR spectral distribution. In this work, Ca3In2Ge3O12:xNd3+ (CIG:xNd3+) and Ca3-x In1.93Ge3O12:0.07Cr3+,yNd3+ (CIG:0.07Cr3+,yNd3+) phosphors are successfully prepared via a high-temperature solid-state method. CIG:0.07Cr3+ shows broadband emission centered at 804 nm, which covers most of the excitation peaks of Nd3+ ions. Under excitation at 480 nm, Cr3+ can provide effective energy transfer to Nd3+. In addition, CIG:0.07Cr3+,0.15Nd3+ has good temperature stability, and maintains 68.98% of the room-temperature intensity at 150 °C. The phosphors can convert short-wave photons to long-wave photons and enhance solar cell utilization, demonstrating the potential application of this material in solar spectral conversion technology.

A new direct band gap Si-Ge allotrope with advanced electronic and optical properties.

Direct-band silicon materials have been a sought-after material for potential applications in silicon photonics and solar cells. Accordingly, methodologies like nanostructure engineering, alloy engineering and strain engineering have been developed. In this work, the particle swarm optimization (PSO) algorithm is used to design direct-band Si-Ge alloys. The findings of phonon computations demonstrate that all these structures are dynamically stable. In addition, ab initio molecular dynamics and elastic constant calculations are carried out, with results indicating these structures are thermodynamically stable at 300 K, as well as being mechanically stable. All of these materials exhibit semiconductor behavior with band gaps of 1.03, 0.68 and 1.37 eV for α, β and γ phases, respectively, at the HSE06 level. The results of effective mass and mobility of carriers that are important in applications show that holes are more easily transported in all structures, with higher concentration of holes accompanied by lower carrier mobility. Different concentrations of holes nh lead to different limits in the scattering process. When nh is lower than the value of around 1016 cm-3, deformation potential scattering is dominant, while the ionized impurity scattering process limits overall mobility when nh is higher than such a value. Finally, the absorption spectra shows that both α and β phases have isotropic optical properties in the X- and Y-directions while strong anisotropy can be seen in the Z-direction. However, the γ phase exhibits no notable isotropy. This investigation finds three direct-band and potentially CMOS compatible materials, a finding which will benefit the development of high efficiency emitters or solar cells.

Physical and photovoltaic characteristics of copper oxide thin films as hole-selective layers for screen-printed mono-crystalline silicon solar cell applications

Copper oxide (CuO4.8) is proposed as a hole-selective layer (HSL) for screen-printed mono-crystalline silicon solar cell (SMSC) applications. The bandgap, work function, and valance band offset (VBO) of the CuO4.8 HSL are presented. The energy band diagram of the P-Si(100)/SiOx/CuO4.8/Ag stacked film is shown. The results indicate an improvement of the conversion efficiency of more than 1.4% absolute from 17.2% to 18.6% for SMSCs with CuO4.8 as the HSL. The promotion mechanism is attributed to the low VBO of the CuO4.8 HSL. Moreover, the surface recombination is reduced by tunneling SiOx formed on the Si surface during CuO4.8 evaporation at a specific ambient oxygen level.

Fabrication and characterization of sputtered Mg and F co-doped ZnO thin films with different substrate temperature for silicon thin-film solar cell applications

Transparent conducting oxide thin films have been extensively studied for various optoelectronic devices. In this paper, we investigated the influence of substrate temperature on structure, morphology, electrical and optical properties of Mg and F co-doped ZnO (MFZO) thin films. The MFZO films were deposited on glass substrates by radio frequency magnetron sputtering at a temperature ranging from room temperature to 200 °C. Experimental results indicate that small amounts of Mg (3 at%) and F (6 at%) co-doping does not change the (002) oriented hexagonal wurtzite structure of ZnO, but it can improve the crystallinity and optoelectronic properties by increasing the substrate temperature. For all MFZO films, the average transmittance in the visible region exceeds 91%. As the substrate temperature rises to 200 °C, the electrical resistivity of the film drops to 1.18 × 10−3 Ω cm. The high figure of merit (FOM) of the film deposited at 200 °C, 1.36 × 10−2 Ω−1 or 2.96 × 104 Ω−1 cm−1, makes it a transparent conductor of choice for photovoltaic applications. By etching with a dilute HCl solution, the surface morphology of the as-deposited MFZO film was modified to a crater-like texture, resulting in a significant increase in the average haze in the visible region from 4.5% to 52.3%. By employing the developed high-FOM and high-haze MFZO film as the front electrode of a-Si:H thin-film solar cells, a 30% increase in conversion efficiency was achieved under AM 1.5 G illumination.

Tuning the optoelectronic properties of AZO thin films for silicon thin film solar cell applications

Al-doped ZnO (AZO) thin films are deposited using dc magnetron sputtering and the process conditions are optimized to obtain transparent conducting electrode (TCE) with desirable properties suitable for photovoltaic applications. In the course, the effects of deposition parameters such as growth temperature, deposition time and plasma power density on the structural and optoelectronic properties were investigated using suitable characterization techniques. XRD analysis of the deposited films at different process conditions showed a strong c-axis preferred orientation. The surface roughness of the deposited films was examined using AFM analysis. Elemental analysis was carried out using XPS. The resistivity and sheet resistance of the thin films decreased with increase in temperature, deposition time and power density. The optimized films deposited at 250 °C resulted in electrical resistivity of 6.23 × 10−4 Ωcm, sheet resistance of 9.2 Ω/□ and exhibited an optical transmittance of &gt;85% in the visible range. Figure of merit (FOM) calculations were carried out to analyze the suitability of deposited thin films for thin film amorphous silicon solar cell applications. The photogain of optimized intrinsic a-Si:H layer was in the range of 104, whereas no photogain was observed in doped a-Si:H layers. The thin film solar cell fabricated using the optimized AZO film as TCE exhibited power conversion efficiency of 6.24% when measured at AM 1.5 condition.

A comprehensive investigation of the potential of metal assisted chemical etched (MACE) nano-textures over conventional micron-sized iso-textures for industrial silicon solar cell applications

We present a comprehensive comparative analysis of acid textured and MACE (Metal Assisted Chemical Etching) nano-textured multi crystalline silicon (mc-Si) solar cells processed in an industrial cell line in terms of performance parameters. The batch average open circuit voltage of nano-textured solar cells was marginally lower and the measures for improving the same are discussed. Batch average short circuit current (JSC) and fill factor (FF) were respectively 0.65 mA-cm−2 and 0.7% (absolute) higher for MACE nano-textured solar cells. Significantly lower surface reflectance in MACE nano-textured cells in the blue and near infrared regions are found to be the reason for the enhancement in JSC. The main component of FF gain is identified as the lower series resistance in MACE cells. The contact formation mechanism in screen printed mc-Si solar cells, investigated using scanning electron microscopy, revealed that the elevated portions at the boundaries of the textures act as favorable sites for silver crystallite precipitation. A larger areal density of such sites is observed on the MACE nano-textured surface than in case of acid textured solar cells, leading to a much lower series resistance. The results suggest the potential for the application of MACE in the more popular mono-crystalline silicon cell technology for further reduction of contact resistance. Alternatively, MACE may be used to obtain similar contact resistance with lower amount of silver paste, compared to iso- and pyramid textured solar cells.