Monocrystalline Silicon Solar Cells Research Articles

Comparative study of different silicon oxides used as interfacial passivation layer (SiNy:H / SiOx /n+-Si) in industrial monocrystalline silicon solar cells

Ultrathin silicon oxide (SiOx) is used as a passivating and tunneling layer in high efficiency passivated contact silicon (Si) wafer solar cells. In this work, the emitter surface passivation quality using a low-cost, low-temperature (40 °C), non-acidic and safe chemical oxide passivation process (named as NCPRE-oxide) grown using sodium hypochlorite solution is compared with other existing oxide growth or deposition processes such as dry thermal oxide, Radio Corporation of America standard clean-2 (RCA-2) chemical oxide, nitric acid based oxide, sulphuric acid based (Piranha) oxide, ozone based oxide and deposited oxide by plasma enhanced chemical vapour deposition on standard 6-inch textured Si wafers. All the oxides layers are capped with hydrogenated amorphous silicon nitride (SiNy:H) improve passivation of the n+-type Si surface. There is a substantial improvement in the effective minority carrier lifetime (τeff) for SiOx/SiNy:H stack on the phosphorous diffused pyramidal textured Si surface. Further, to compare the influence of NCPRE-oxide process with other oxide processes on the electrical performance of the final device, these different processes were included in the fabrication of large area industrial aluminum-back surface field (Al-BSF) solar cells. A comprehensive analysis based on ellipsometry for film thickness measurement, τeff measurement, cell current-voltage characteristics, photoluminescence imaging, internal quantum efficiency mapping, and front surface recombination velocity measurement is presented. The NCPRE-oxide process resulted in a similar improvement in passivation and cell efficiency as other oxide processes for Al-BSF cells. In addition, its low-cost, low thermal budget, easy waste disposal, and single-component nature make it viable for industrial scale implementation.

Metal Cations in Efficient Perovskite Solar Cells: Progress and Perspective.

Metal halide perovskite solar cells (PVSCs) have revolutionized photovoltaics since the first prototype in 2009, and up to now the highest efficiency has soared to 24.2%, which is on par with commercial thin film cells and not far from monocrystalline silicon solar cells. Optimizing device performance and improving stability have always been the research highlight of PVSCs. Metal cations are introduced into perovskites to further optimize the quality, and this strategy is showing a vigorous development trend. Here, the progress of research into metal cations for PVSCs is discussed by focusing on the position of the cations in perovskites, the modulation of the film quality, and the influence on the photovoltaic performance. Metal cations are considered in the order of alkali cations, alkaline earth cations, then metal cations in the ds and d regions, and ultimately trivalent cations (p- and f-block metal cations) according to the periodic table of elements. Finally, this work is summarized and some relevant issues are discussed.

Lead‐Free Tin‐Based Perovskite Solar Cells: Strategies Toward High Performance

Perovskite solar cells (PSCs) have achieved state‐of‐the‐art efficiency, approaching monocrystalline silicon solar cells due to the superior optoelectronic properties and intensive research efforts, fulfilling its forthcoming commercial use at affordable costs. Nevertheless, the toxicity of lead (Pb) is still one of the obstacles hindering future large‐scale production. Herein, the recent progress of emerging lead‐free tin (Sn)‐based PSCs is reviewed. First, the structural and photovoltaic‐related properties of Sn‐based perovskites are summarized. Following a brief introduction of film deposition methods, strategies recently adopted to obtain high performance are then discussed in detail. Finally, the current challenges and prospective opportunities are provided to help the further progression of Sn‐based PSCs.

Study and analysis the Cu nanoparticle assisted texturization forming low reflective silicon surface for solar cell application

Monocrystalline silicon solar cells with photo-absorbing morphology can amplify light-trapping properties within the absorber layer and help to fabricate cost-effective solar cells. In this paper, the effect of different parameters namely temperature and time of Cu-assisted chemical etching was thoroughly investigated for the optimization of the light absorption properties. P-type monocrystalline wafers were selectively treated with Cu(NO3)2.3H2O:HF:H2O2:DI water solution at 50 °C for five different time duration. The entire process was repeated at five different temperatures for 20min as well to study the relation between etching temperature and surface reflectance. Sonication bathing was used for the removal of the deposited Cu atoms from the surface with the variation of time and the effect was examined using energy dispersive spectroscopy (EDS). Field emission scanning electron microscopy (FESEM) and UV/VIS spectroscopy were conducted to study the surface morphology and light absorbance respectively. Inverted shapes almost similar to inverted pyramids or porous surface were found randomly on the surface of the wafer. The effect of temperature was found more significant compared to the effect of time variation. An optimum light reflectance was found at 50 °C for 20 min of texturization. Atomic force microscopy (AFM) of the textured sample revealed the average depth of pyramidal shape was about 1.58 μm. EDS results showed a proportional relation between time and Cu removal process, and a complete Cu atoms free textured surface after 25 min of sonication bathing. Therefore, a suitable Cu-assisted texturization technique was found, which could enable lowering the photo-reflectance below 1% without any antireflection coating.

Evaluation the Performance of CPV with Different Concentration Ratio

The present work aims at decrease the cost of the photovoltaic (PV) solar system by decreasing the area of expensive solar cells by low cost optical concentrators that give the same output power. Output power of two types’ monocrystalline and polycrystalline silicon solar cells has been measured with and without presence of linear focus Fresnel lenses (FL) with different concentration ratios. Cooling system has been used to decrease the effect of temperature on solar cell performance. The results indicated that the increase in the output power is about 5.3 times by using Fresnel lens concentrator without using cooling system in comparison with solar cell without concentrator, while it is about 14.6 times by using cooling system. The efficiency of monocrystalline solar cell without cooling system is about 11.2% for solar irradiance 0.698 kW/m2, this value decrease to 3.3% for solar irradiance 12.4 kW/m2 and concentration ratio 17.7 by using Fresnel lens concentrator, while when using cooling system the efficiency enhance to 12.9% and 8.8% for solar irradiance 0.698 and 12.4, respectively.

Optimization of ALD $$\hbox {Al}_{2}\hbox {O}_{3}$$ process parameters for passivation of c-silicon and its implementation on industrial monocrystalline silicon solar cell

Effect of process parameters on \(\hbox {Al}_{2}\hbox {O}_{3}\) deposited using Atomic Layer Deposition (ALD) for the surface passivation of c-silicon surface has been investigated. Surface passivation properties of \(\hbox {Al}_{2}\hbox {O}_{3}\) have been measured by evaluating the minority carrier lifetime and interface charges at the \(\hbox {Si}/\hbox {Al}_{2}\hbox {O}_{3}\) interface. It has been observed that surface passivation properties of \(\hbox {Al}_{2}\hbox {O}_{3}\) are strongly dependent on process parameters such as substrate temperature, annealing temperature, and thickness of the deposited \(\hbox {Al}_{2}\hbox {O}_{3}\) film. Minority carrier lifetime, effective charge density (\(Q_{{\mathrm{eff}}}\)), and interface defect density (\(D _{{\mathrm{it}}}\)) were observed to vary from 180 to \(355\,\upmu \hbox {s}\), \(-\,2.3 \times 10^{12}\) to \(-1.46 \times 10^{13}\,\hbox {cm}^{-2}\) and \(1.2 \times 10^{9}\) to \(1.9\times 10^{10}\,\hbox {eV}^{-1}\,\hbox {cm}^{-2}\), respectively, for various process parameters. \(\hbox {Al}_{2}\hbox {O}_{3}\) film based on the optimized process parameters were then used as a passivation layer in fabricating industrial PERC solar cells. Effect of \(\hbox {Al}_{2}\hbox {O}_{3}\) passivation in PERC solar cells has been demonstrated by comparing the characteristics of the PERC solar cells with that of the standard Al BSF solar cells. An efficiency improvement of \(\sim 0.8\%\) has been observed in passivated emitter rear cells (PERC) solar cells as compared to the standard aluminum back surface field (Al BSF) solar cells.

Improved photovoltaic performance of monocrystalline silicon solar cell through luminescent down‐converting Gd2O2S:Tb3+ phosphor

AbstractThis work reports on efforts to enhance the photovoltaic performance of standard p‐type monocrystalline silicon solar cell (mono‐Si) through the application of ultraviolet spectral down‐converting phosphors. Terbium‐doped gadolinium oxysulfide phosphor and undoped‐gadolinium oxysulfide precursor powders were prepared by a controlled hydrothermal decomposition of a urea homogeneous precipitation method. The resulting rare‐earth element hydroxycarbonate precursor powders were then converted to the oxysulfide by annealing at 900°C in a sulfur atmosphere. The as‐prepared phosphors were encapsulated in ethylene vinyl acetate co‐polymer resin and applied on the textured surface of solar cell using rotary screen printing. Comparative results from X‐ray powder diffraction, field emission scanning electron microscopy, scanning transmission electron microscopy, and photoluminescence spectroscopy studies on the microstructure and luminescent properties of the materials are reported. We also compared the optical reflectance and external quantum efficiency response of the cells with and without a luminescent phosphor layer. The results obtained on the terbium‐doped gadolinium oxysulfide phosphor show clearly that the down‐conversion effect induced by the terbium dopant play a crucial role in enhancing the photovoltaic cells' performance. Under an empirical one‐sun illumination, the modified cells showed an optimum enhancement of 3.6% (from 16.43% to 17.02%) in conversion efficiency relative to bare cells. In the concentration range of 1 to 2.5 mg/mL, EVA/Gd2O2S (blank) composites also improve electrical efficiency, but not as much as EVA/Gd2O2S:Tb3+ composites.

Optical properties of a random inverted pyramid textured silicon surface studied by the ray tracing method

The random inverted pyramid texture has been extensively studied experimentally in high-efficiency monocrystalline silicon solar cells due to its superior optical properties. In this paper, a random inverted pyramid structure model was established, and the optical performance was studied by the ray tracing method. It has five common light paths and can achieve lower reflectance than random upright pyramids. To further analyze the optical properties of random inverted pyramids, a simplified random inverted pyramid model, which consists of two overlapping inverted pyramids, was studied and analyzed in detail. The proportions of the light path related to different overlapping regions, and the reflectance ranging from 10.11% to 10.64%, can be obtained, which is lower than the reflectivity of random upright pyramids. We believe that the random inverted pyramid texture can have a wide range of applications in high-efficiency monocrystalline silicon solar cells.

Effect of doping profile on sheet resistance and contact resistance of monocrystalline silicon solar cells

This paper presents the preparation and characterization of phosphorous-doped silicon solar cells based on screen-printed technique with systematically changing the phosphorous doping concentration. In the work, P-type monocrystalline (100) oriented Czochralski Si wafers of the thickness of 200 μm were textured using wet alkaline solution. Phosphorous was doped on Si wafers employing the diffusion technique with a fixed flow rate of liquid phosphorus oxychloride (POCl3) at the changing diffusion time of 10 min, 15 min and 20 min, respectively. Four-point probe method was adopted to measure the sheet resistance of doped wafers that resulted in significant decrease in the sheet resistance. Moreover, the doping concentration of phosphorus atoms estimated by energy-dispersive x-ray spectroscopy (EDS) analysis as well as Hall Effect measurement found to increase with increasing doping time. Furthermore, the increasing and decreasing of the front contact and back contact resistance with increasing doping concentration was confirmed by the measured contact resistance for different doping densities of the cells using transmission line method (TLM). Thus, the study on the controllable sheet resistance and contact resistance by varying the doping concentration may assist in the commercialization of efficient crystalline Si solar cell.

Design, Optimization and Characterisation of IBC c-Si (n) Solar Cell

The integrated-back contact (IBC) solar cell has attracted wide attention due to its high conversion efficiency, low processing temperature, and thinner substrate from the emerging light trapping of silicon on the pyramidal textured surface. In this paper, a novel IBC solar cell design optimization based on the n-type crystalline silicon wafer was simulated in 2D using Silvaco TCAD tools and the obtained results were compared to the recently published works which allow us to identify the optimum IBC solar cell configuration. In addition, the 2D simulation results are compared to the obtained results by IMEC using SolayTec’ ALD (atomic layer deposition) technique. The numerical simulation leads to attaining 24.79% conversion efficiency and 726 mV open-circuit voltage for the considered n-type mono-crystalline silicon solar cell under the AM1.5 spectrum.

Study and analysis of the morphological, elemental and electrical properties of phosphorus doped monocrystalline silicon solar cell

In this study, the impact of diffusion time on monocrystalline silicon solar cell has been analysed morphologically, elementally, and electrically by adjusting diffusion time to establish optimized properties for high-efficiency. P-type raw wafers were prepared for diffusion following cleaning and wet etching operation. POCl3 diffusion was done by varying diffusion time with a constant flow rate of process gases. The morphological and elemental studies were carried out with scanning electron microscope (SEM), and energy dispersive x-ray spectroscopy (EDX) respectively. Four-point probe test and Hall Effect measurement were used for studying the electrical characteristics (sheet resistance, resistivity, conductivity, and bulk concentration). From SEM result analysis, noticeable structural damages were found with the increase of doping time. Surface reflectance measurement (SRM) also supported the morphological distortion. Phosphorus, oxygen, silicon, and boron were traced by EDX analysis. The formation of phosphosilicate glass (PSG), as well as the depth of emitter, has been confirmed from the elemental analysis. The emitter length was varied from 2.5 μm to 9 μm. 5 min doped sample showed minimum surface deformation with maximum light absorbance. An acceptable sheet resistance with a compatible conductivity, mobility, and bulk concentration are also found for 5 min diffusion, which could potentially lead to high-efficient solar cell fabrication.

The progression of silicon technology acting as substratum for the betterment of future photovoltaics

To solve energy crisis, generation of clean and renewable energy sources are highly recommended. It not only solve energy-related matters but also resolves environmental issues. A great number of renewable energy sources are present nowadays to resolve aforementioned issues, out of which photovoltaic modules is the preferable technology over others. Silicon is the native element to be used in photovoltaic module, due to its reasonable cost and band gap. The deciding parameters to harness solar energy to electricity rely upon solar irradiance and weather conditions. Here, we describe the rapid transformation of silicon as photovoltaic solar cell material that transfigured the photovoltaic industry. The photovoltaic industry initiated with monocrystalline silicon and multicrystalline silicon solar cell having conversion efficiency reached up to approximately 22.9% and 20.8%, respectively. The contemporary outburst for the trade of photovoltaic industry is due to the high manufacturing cost of silicon solar panels, which provided a chance for researchers to quest for advanced technology. It gave an opportunity for thin film solar cell to infiltrate in the market. This technology reduced the cost but on the expense of lower conversion efficiency.

Correction to: Non-destructive Testing of a Monocrystalline Silicon Solar Cell: Magnetic Field - Electrical Properties Correlation

Due to an oversight, the author incorrectly labeled the axis in Fig. 5 of the published online version.

Active area cell efficiency (19%) monocrystalline silicon solar cell fabrication using low-cost processing with small footprint laboratory tools

A high efficiency (> $$18\%$$ ) industrial large area crystalline silicon wafer solar cell fabrication process generally requires industrial equipment with large footprint, high capital and running costs. Stricter processing window, continuous monitoring and automated functioning are the reasons for it. However, for any conventional laboratory (lab) it is always difficult to manage these requirements with limited available lab space or insufficient fund and other related resources. In this work, we report a novel way to fabricate high efficiency full area aluminium back surface field monocrystalline silicon wafer solar cells in our lab using low-cost processing with small-footprint fabrication tools for 6 inch pseudo-square industrial wafers. The novelty of our work includes optimization of every fabrication process step, e.g., texturization, emitter diffusion, emitter passivation and anti-reflection coating deposition, edge-isolation, screen printing and co-firing individually. These modifications include tuning of processing tools and processes, utility changes and inclusion of additional process steps. Beaker-based chemical processes, manual diffusion furnace, introduction of low temperature oxidation, low temperature silicon nitride deposition processes, plasma-edge isolation tool, single manual screen printer, single oven drying of metal pastes and co-firing using rapid thermal processing tools were used at our lab. For our cells, actual and active area efficiencies of 18.5 and 19% (measured under AM1.5G 1 Sun condition), respectively, were achieved.

Photovoltaic and Physical Characteristics of Screen-Printed Monocrystalline Silicon Solar Cells with Laser Doping and Electroplated Copper

Photovoltaic and physical characteristics of screen-printed monocrystalline silicon solar cells (SPMSCs) were presented with electroplated copper (EPC) as the rear contact. The boron back surface field (B-BSF) formed by spin-on doping and laser doping (LD) was prepared as a seed layer for the EPC. The LD parameters, including the laser focus, laser power, laser speed, and laser line pitch, were investigated. Moreover, the effects of KOH etching on the surface properties after the LD process were explored. Furthermore, to enhance the adhesion between the B-BSF seed layer and EPC contact layer, a laser pinhole process was proposed. Finally, the EPC processes with various electroplating times were addressed. The results revealed that the mechanism of enhancements could be attributed to a continuous B-BSF seed layer and a reduction of series resistance, as well as an increase of open-circuit voltage and adhesion between the B-BSF seed layer and EPC contact layer.

Investigation of phosphorus diffused back surface field (BSF) in bifacial nFAB solar cells

Recently bifacial n-type passivated emitter and rear totally diffused (PERT) monocrystalline silicon solar cells have become one hot spot in photovoltaic (PV) industries, due to good bifaciality, high and stabilised conversion efficiency. Unlike passivated emitter and rear contacts (PERC) structure, n-PERT solar cells require the use of a thin and uniform back surface field (BSF) layer, usually achieved by phosphorus doping. In this study, we optimised the phosphorus diffusion process in terms of surface concentration, junction depth and carrier lifetime. The effects of different phosphorus BSF were investigated by fabricating n-type front and back contact (nFAB) PERT solar cells using industrial feasible approaches and M2 size Czochralski (Cz) monocrystalline Si wafers (6 in., 244.32 cm2). Good phosphorus profiles were developed, which gives low parasitic absorption, low contact resistance and low J0 value when passivated with silicon nitride (SiNx) layer. The optimised champion cell shows a high Voc of 666.5 mV, Jsc of 40.2 mA/cm2, fill factor of 79.9%, efficiency of 21.43% from front side-illumination, together with a good bifaciality factor of 93.0%.

The Influence of the EVA Film Aging on the Degradation Behavior of PV Modules Under High Voltage Bias in Wet Conditions Followed by Electroluminescence

The influence of the ethylene-vinyl acetate (EVA) film quality on potential induced degradation was studied on in-house developed mini modules with p -type monocrystalline silicon solar cells. The modules were assembled with EVA films of equivalent qualities, but different ages and exposed to an accelerated test (relative humidity = 85%, T = 60 °C, Vbias = +1000 V). The age of the EVA film was determined from the time we received the EVA film, and opened the sealed enclosure and the time of lamination. After the EVA film was removed from the sealed enclosure, it was kept in a dark place at room temperature. The storage times of the “fresh,” “aged,” and “expired” films were: less than 14 d, around 5 mo, and more than 5 years, respectively. While modules with a “fresh” EVA film exhibit almost no degradation, the modules with the “aged” EVA film degrade very rapidly and severely. Their degradation rate was around 0.2%/d during the 2000 h of damp heat test. We also observed a strong silver line corrosion, which occurs because of the peroxide leftovers in the “aged” EVA films.

Crack detection in monocrystalline silicon solar cells using air-coupled ultrasonic lamb waves

In recent years, solar energy becomes one of the most popular renewable energy resources. Among the solar energy systems, solar cells are considered to be one of the most critical components, which are naturally fragile during either fabrication or service. Thus, nondestructive examination of solar cells is required practically. In this research, solar cells made from monocrystalline silicon are selected as the typical samples. The air-coupled ultrasonic nondestructive testing system, based on the generation and reception of the A0 mode Lamb waves, will be adopted for defects detection. Firstly, the dispersion curves of Lamb waves in anisotropic monocrystalline silicon are calculated theoretically, which provides a theoretical foundation for analyzing the behavior of Lamb waves propagating in silicon solar cells. Then, experiments on monocrystalline silicon solar cells are carried out by introducing the air-coupled ultrasonic Lamb waves. The amplitude distributions of Lamb waves propagating along various rotation angles in silicon solar cells are obtained. It shows a strong anisotropic properties of the tested samples. Finally, artificial cracks in solar cells are scanned circularly and laterally. The results of amplitude distributions give the scattering pattern of cracks, which can be used to determine whether the crack breaks through or not. And the extracted amplitude cross-correlation coefficients can help to estimate the length of them.

Plasma-produced ZnO nanorod arrays as an antireflective layer in c-Si solar cells

In this work, we develop a simple customized radio-frequency plasma-enhanced horizontal tube furnace deposition system to directly grow high-quality ZnO nanorod arrays on zinc films and investigate their application as an antireflective layer in n+pp+ monocrystalline silicon (c-Si) solar cells. Field emission scanning electron microscope, X-ray diffractometer, and transmission electron microscope studies reveal that ZnO nanorod arrays feature a perfect crystalline wurtzite structure and grow preferentially along [0001] direction. The antireflective performance of ZnO nanorod arrays is confirmed by Fresnel coefficient matrix method and MATLAB software calculation. Furthermore, PC1D simulation demonstrates that the photovoltaic property for c-Si solar cells of the pyramid-textured front surface using ZnO nanorod arrays as an antireflective layer is much better than that for the other three types of c-Si solar cells (i.e., c-Si solar cells of the pyramid-textured front surface without using any antireflective layer, c-Si solar cells of the planar front surface using ZnO nanorod arrays as an antireflective layer, as well as c-Si solar cells of the planar front surface without using any antireflective layer). In particular, the photovoltaic conversion efficiency of 20.23% has been achieved for c-Si solar cells of the pyramid-textured front surface using ZnO nanorod arrays as an antireflective layer. This work is highly relevant to the development of an advanced process for the realization of high-efficiency, low-cost, and stable solar cells.

Numerical Analysis of the Optical Contribution of Rear Passivation Layers to the Photo-Generated Current of Monocrystalline Silicon Solar Cells

Numerical Analysis of the Optical Contribution of Rear Passivation Layers to the Photo-Generated Current of Monocrystalline Silicon Solar Cells