Heterojunction With Intrinsic Thin-layer Research Articles

Performance assessment of different photovoltaic module technologies in floating photovoltaic power plants under waters environment

The paper undertakes a novel study that aims to analyze the performance characteristics of ten monocrystalline or polycrystalline silicon modules employing different emerging technologies in waters environment. In this work, monitoring data were collected over a duration of one year using a multi-technology empirical platform within a floating photovoltaic power plant. The energy performance of different module technologies was evaluated using multiple performance metrics such as array yield, performance ratio, capacity factor, efficiency and energy density. By considering environmental variables such as irradiance, ambient temperature, and water temperature, the thermal behavior of photovoltaic modules under water surface deployment conditions is revealed. Furthermore, the multiple variable coupling analysis was conducted to determine the correlation between the performance metrics of various technology type modules and meteorological variables in waters environment. The results indicate that the energy performance and reliability of monocrystalline silicon modules using double-glass double-sided P-type PERC technology is superior to other technologies in waters environment, and the performance ratio and capacity factor reach 88.95 % and 15.04 %, respectively. The heterojunction with intrinsic thin-layer (HIT) technology module exhibits better thermal stability and holds an advantage in the deployment of limited water surface areas due to its higher energy density. Moreover, the performance ratio of floating photovoltaic systems shows a weak correlation with irradiance, and is more significantly affected by the negative correlation of ambient temperature than water temperature.

Solar Photovoltaic Parameter Extraction for Three Different Technologies Using Particle Swarm Optimization Method

Industry and academia are becoming more interested in solar energy. The problem of providing an alternative to fossil fuels and limiting the environmental damage brought on by their emissions is what has brought about this increased focus. Solar photovoltaic is the subject of a growing number of studies. The goal of the current investigation is to investigate how various technological modules namely single junction amorphous silicon (a-Si), Hetero junction with Intrinsic Thin-layer (HIT) and multi crystalline silicon (mc-Si) are affected by seasonal spectrum variation respond to Indian climatic circumstances. Compared to many other nations, the entire Indian subcontinent has a relatively distinct climate with distinct seasonal patterns. The four seasons that are considered in this study are summer, winter, monsoon, and post monsoon. The impact of each season varies on the spectrum. Such a study will be helpful to measure the parameter connected to the spectrum and assess its impact on the effectiveness of the PV array. In order to conduct accurate performance investigations, the extraction of the right circuit model parameters is essential. The estimation of the solar PV parameter is done by using Particle swarm optimization (PSO) algorithm.

Research progress of light and elevated temperature-induced degradation in silicon solar cells: A review

At present, passivated emitter and rear cell (PERC) solar cells dominate the photovoltaic industry. However, light and elevated temperature-induced degradation (LeTID) is an important issue responsible for the reduction of PERC efficiency, which may lead to up to 16% relative performance losses in multicrystalline silicon solar cells, and this degradation occurs in almost all types of silicon wafers. Even in next-generation silicon solar cells like Tunnelling oxide passivated contact (TOPCon) and Heterojunction with Intrinsic Thin-layer (HJT) solar cells, LeTID can still cause an efficiency loss up to 1% relative. LeTID is a long process in terms of time during the whole cycle of degradation and regeneration, which will seriously affect the conversion efficiency and stability of solar modules, and hence increase the cost of electricity generated by solar cells. Furthermore, after years of research on LeTID, researchers are yet to determine the specific cause of LeTID. In this paper, we refer to specific literature, briefly describe the development history of LeTID, introduce the phenomena of LeTID in crystalline silicon solar cells, and describe its characteristics. In addition, we also analyzed the fundamental causes of LeTID, and found that the cause may be related to metal impurities or hydrogen contained in solar cells. At present, in view of the participation of hydrogen in LeTID and other existing related theories, this paper introduces several methods to inhibit LeTID in crystalline silicon. Finally, the content of this paper is summarized, and the development of solar cells in the future is prospected.

Admittance spectra of silicon photocells in dark mode

An extended model of silicon photovoltaic cells with localized parameters is presented, including inductance in a series branch. Based on the recorded admittance-frequency spectra, the dependences of the active and reactive components from the bias voltage for PERC (Passivated Emitter Rear Cell), HIT (Heterojunction with Intrinsic Thin-layer solar cells) and IBC (Interdigitated Back Contact cells) elements are reconstructed. The structure of the Nyquist diagrams for the components of admittance spectra is analyzed, which make it possible to visually determine the working scheme of the chain based on the elementary links of the first and second orders.

МОДЕЛИРОВАНИЕ ГЕТЕРОСТРУКТУРНОГО СОЛНЕЧНОГО ЭЛЕМЕНТА A-SI:H(N)/A-SI:H(I)/C-SI(P)

In this work, a silicon solar cell HIT (heterojunction with intrinsic thin-layer) a-Si:H(n)/a-Si:H(i)/c-Si(p) was simulated using AFORS-HET software. The influence of layer thickness and temperature of the solar cell under study on its photovoltaic characteristics is discussed. When optimizing the above characteristics, its effectiveness reaches a value of 19.1%. The results obtained are the foundation for further scientific and technological research on the development of highly efficient silicon solar cells.

Synergetic or colliding effects on the solar-electric conversion efficiency from light-trapping structured surfaces: Coupling optical-electrical features of bifacial solar cells

Light-trapping structures play an important role in the application of solar cells due to their ability to enhance absorption. A dilemma related to comprehensive consideration of augmenting the light-trapping ability of surfaces of solar cells and suppressing recombination tendency induced by improper design of structured surfaces to keep in mind the ultimate goal of achieving as high solar-electric conversion efficiency of commercial photovoltaic cells as possible. This work is aimed at investigating the coupling optical-electrical properties of bifacial heterojunction with intrinsic thin-layer (HIT) solar cells on which multiscale pyramid microstructures are fabricated. Based on the results of coupling investigation, a tradeoff between optical and electrical properties are achieved with pyramids of 3–5 μm. The highest power conversion efficiency (PCE) locates at solar cells with pyramids of 3–5 μm. The best PCE amounts respectively to 23.46% and 21.85% with the frontal and rear illumination and the bifacial utilization can be enhanced is up to 93.4%. The output properties are superior to those of PV cells in the baseline. The interconnection between the temperature coefficient of PV conversion efficiency and dimensions of the microstructured surfaces is studied. The influences of different light-trapping structures on the ability of photon absorption and the recombination of carriers of solar cells are characterized. This work provides the guideline for selecting more appropriate structures with both benign optical and electrical properties to enhance the performance of solar cells.

고효율 Silicon Heterojunction Solar Cell을 위한 Indium Tin Oxide 연구

HIT (heterojunction with intrinsic thin-layer) solar cells are in the spotlight as ultra-high efficiency solar cells. While an a-Si: H (i) (intrinsic hydrogenated amorphous silicon) layer is important for high quality passivation layers, the TCO (transparent conductive oxide) has also become important. This paper describes the changes in the properties of ITO (indium tin oxide) in HIT solar cells. ITO is used as a TCO because of its high transmittance and conductivity at thin thickness. On the other hand, a relatively high free carrier concentration and low mobility are disadvantageous compared to other TCOs. To improve the properties of ITO, a method of diversifying the deposition process and subsequent heat treatment has been proposed. Alternatively, IZO (indium zinc oxide), IO: H (hydrogen doped indium oxide), IWO (indium tungsten oxide), and ITiO (indium titanium oxide), etc. have been used as TCOs to replace ITO.

Performance evaluation of 830 kWp grid-connected photovoltaic power plant at Kamuzu International Airport-Malawi

The paper presents performance evaluation for 830 kWp grid-connected PV power plant at Kamuzu International Airport in Malawi. The study used both measured and simulated data for the period September 2013 to August 2017. The PV array comprises 3540 solar modules of Heterojunction with Intrinsic Thin-layer (HIT) technology; each module was rated 235 Wp and tilted at 30°. The annual four-year average array, inverter and overall system efficiencies were 15.3%, 95.2% and 14.6%, respectively. An average annual capacity factor of 17.7% was obtained and the annual four-year average performance ratio was 79.5%. The results from this study are compared with those of representative PV power plants reported elsewhere.

Effect of additional HfO2 layer deposition on heterojunction c‐Si solar cells

AbstractThe efficiency of a heterojunction with intrinsic thin‐layer (HIT) solar cell with an insulator/ITO structure was discussed in this paper. First, the efficiency was analyzed by OPAL 2 simulations. Second, an insulator/ITO structure was experimentally applied to a HIT solar cell. The OPAL 2 simulations using an insulator/ITO/Si structure and a TCO/ITO/Si structure showed that the generation current density in the Si substrate increased when the insulator or TCO layer had a proper thickness. Experimentally, HfO2, a type of insulator, was deposited on a HIT solar cell with a thickness varying from 3 to 15 nm. The average efficiency of the HIT solar cell improved from 18.21% to 20.75% after HfO2 deposition. The highest efficiency was achieved for the 3‐nm‐thick HfO2/HIT solar cell structure, which exhibited the best improvement in the current density of approximately 1.5 mA/cm2. For the external quantum efficiency of the HfO2/HIT solar cell, the total absorption was improved by HfO2 deposition. The results suggest that the HfO2 layer improves the solar cell efficiency of the HIT solar cell by increasing light absorption.

Evaluation of the performance and degradation of crystalline silicon-based photovoltaic modules in the Saharan environment

The aim of this paper is to present three years of an evaluation of the performance and degradation rate of three different crystalline silicon-based photovoltaic (PV) modules in the Saharan environment. The PV modules are: mc-Si (multi-crystalline), c_Si (mono-crystalline, back contacted) and HiT (heterojunction with intrinsic thin-layer); they are installed in Saida which is located at the proximity of Algeria’s Sahara. Two methods were used to calculate the degradation rate; the effective peak power of the PV modules and the temperature corrected performance ratio. It was found that the HIT technology performs worse than the other technologies with the highest degradation rate, ranging from −1.53%/year to −1.92%/year. The mc_Si PV and c_Si PV module technologies present a lower degradation rate than the HIT technology in the range of −0.74%/year to −0.83%/year and −0.58%/year to −0.79%/year respectively.

Research on the Structure, General Design and Operational Mechanism of Energy Internet

能源互联网是解决当前能源紧缺和环境污染问题的重要手段之一，是推动我国能源革命的重要战略支撑。构建合理的网络构架，选择最优的总体设计方案，是能源互联网取得长足发展的前提和基础。以分布式冷热电三联供系统、储能型高效HIT光伏电站、低风速风力发电、分布式智能电网系统、智慧能源生活社区、源网荷储协调控制等为技术依托，拟定能源互联网的整体构架；基于扬州宝应西安丰镇实验基地的实验研究，选择合适的电能转化机制，制定详细的总体设计方案；依据设计方案制定能源互联网的运行机制，实现电力交易的多元化。 Energy Internet is one of the effective means to solve the immediate problems of energy shortage and environmental pollution. And it is an important strategic support for China’s energy revolution. Establishing an applicable structure and selecting the optimal design are the basis of the development of Energy Internet. Firstly, the whole structure of Energy Internet is proposed relying on the technology of distributed cold and heat power supply system, energy storage type of efficient Heterojunction with intrinsic Thinlayer (HIT) photovoltaic power station, wind power generation at low wind speed, distributed smart grid, smart energy living community and coordinative control of generation-grid-load-storage. Secondly, the general plan is formulated in the experimental base. Lastly, the operational mechanism is established to make power transactions diversified.

Wind Effect Modeling and Analysis for Estimation of Photovoltaic Module Temperature

The performance of photovoltaic (PV) modules in outdoor field conditions is adversely affected by the rise in module operating temperature. Wind flow around the module affects its temperature significantly, which ultimately influences the module output power. In this paper, a new approach has been presented, for module temperature estimation of different technology PV modules (amorphous Si, hetero-junction with intrinsic thin-layer (HIT) and multicrystalline Si) installed at the site of National Institute of Solar Energy (NISE), India. The model based on presented approach incorporates the effect of wind speed along with wind direction, while considering in-plane irradiance, ambient temperature, and the module efficiency parameters. For all the technology modules, results have been analyzed qualitatively and quantitatively under different wind situations. Qualitative analysis based on the trend of module temperature variation under different wind speed and wind direction along with irradiance and ambient temperature has been presented in detail from experimental data. Quantitative results obtained from presented model showed good agreement with the experimentally measured data for different technology modules. The model based on presented approach showed marked improvement in results with high consistency, in comparison with other models analyzed for different technology modules installed at the site. The improvement was very significant in case of multicrystalline Si technology modules, which is most commonly used and highly temperature sensitive technology. Presented work can be used for estimating the effect of wind on different technology PV modules and for prediction of module temperature, which affects the performance and reliability of PV modules.

N-type compensated silicon: resistivity, crystal growth, carrier lifetime, and relevant application for HIT solar cells

N-type compensated silicon shows unusual distribution of resistivity as crystal grows compared to the n-type uncompensated silicon. In this paper, evolutions of resistivities with varied concentrations of boron and varied starting resistivities of the n-type silicon are intensively calculated. Moreover, reduction of carrier mobility is taken into account by Schindler’s modified model of carrier mobility for the calculation of resistivity of the compensated silicon. As for substrates of solar cells, optimized starting resistivity and corresponding concentration of boron are suggested for better uniformity of resistivity and higher yield (fraction with ) of the n-type compensated Cz crystal rod. A two-step growth method is investigated to obtain better uniformity of resistivity of crystal rod, and this method is very practical especially for the n-type compensated silicon. Regarding the carrier lifetime, the recombination by shallow energy-level dopants is taken into account for the compensated silicon, and evolution of carrier lifetime is simulated by considering all main recombination centers which agrees well with our measured carrier lifetimes as crystal grows. The n-type compensated silicon shows a larger reduction of carrier lifetime compared to the uncompensated silicon at the beginning of crystal growth, and recombination with a oxygen-related deep defect is sufficient to describe the reduction of degraded lifetime. Finally, standard heterojunction with intrinsic thin-layer (HIT) solar cells are made with substrates from the n-type compensated silicon rod, and a high efficiency of 22.1% is obtained with a high concentration () of boron in the n-type compensated silicon feedstock. However, experimental efficiencies of HIT solar cells based on the n-type compensated silicon show an average reduction of 4% along with the crystal length compared to the uncompensated silicon. The obtained results enrich our knowledge on the n-type compensated silicon and contribute to the development of n-type compensated silicon-based solar cells for commercial application.

High Efficiency Computer Simulation for Au/n-ZnO/p-Si/Al Schottky-Type Thin Film Heterojunctions

In this paper, the Au/n-ZnO/p-Si/Al heterojunction for developing solar cells with high conversion efficiency and low cost were studied. The Au/n-ZnO/p-Si/Al HIT (heterojunction with intrinsic thin-layer) solar cells were analyzed and designed by AFORS-HET software. The characteristics of such cells with emitter intrinsic layer thickness and interface states density are discussed. The simulation results show that the key role of the intrinsic layer inserted between the ZnO and crystalline silicon substrate p-Si is to decrease the interface states density. If the interface states density is lower than 1010 cm−2.V−1, a thinner intrinsic layer is better than a thicker one. The increase of the thickness of the emitter will decrease the short-current density and affect the conversion efficiency. The effect of Surface Recombination Velocity (SRV) front and back on the J-V characteristics of the Au/n-ZnO/p-Si/Al heterojunction solar cell has been studied with this simulation. With the optimized parameters set, the Au/n-ZnO/p-Si/Al solar cell reaches a high efficiency (η) up to 21.849 % (FF: 0.834, Voc: 0.666 V, Jsc: 39.39 mA/cm2).

Influence of Deposition Pressure on the Properties of Round Pyramid Textured a-Si:H Solar Cells for Maglev.

HIT (Heterojunction with Intrinsic Thin-layer) photovoltaic cells is one of the highest efficiencies in the commercial solar cells. The pyramid texturization for reducing surface reflectance of HIT solar cells silicon wafers is widely used. For the low leakage current and high shunt of solar cells, the intrinsic amorphous silicon (a-Si:H) on substrate must be uniformly thick of pyramid structure. However, it is difficult to control the thickness in the traditional pyramid texturing process. Thus, we textured the intrinsic a-Si:H thin films with the round pyramidal structure by using HNO3, HF, and CH3COOH solution. The characteristics of round pyramid a-Si:H solar cells deposited at pressure of 500, 1000, 1500, and 2000 mTorr by PECVD (Plasma Enhanced Chemical Vapor Deposition) was investigated. The lifetime, open circuit voltage, fill factor and efficiency of a-Si:H solar cells were investigated with respect to various deposition pressure.

The temperature dependence of the characteristics of crystalline-silicon-based heterojunction solar cells

Temperature dependences of the photovoltaic characteristics of (p)a-Si/(i)a-Si:H/(n)c-Si singlecrystalline- silicon based heterojunction-with-intrinsic-thin-layer (HIT) solar cells have been measured in a temperature range of 80–420 K. The open-circuit voltage (VOC), fill factor (FF) of the current–voltage (I–U) characteristic, and maximum output power (Pmax) reach limiting values in the interval of 200–250 K on the background of monotonic growth in the short-circuit current (ISC) in a temperature range of 80–400 K. At temperatures below this interval, the VOC, FF, and Pmax values exhibit a decrease. It is theoretically justified that a decrease in the photovoltaic energy conversion characteristics of solar cells observed on heating from 250 to 400 K is related to exponential growth in the intrinsic conductivity. At temperatures below 200 K, the I–U curve shape exhibits a change that is accompanied by a drop in VOC. Possible factors that account for the decrease in VOC, FF, and Pmax are considered.

Numerical simulation of silicon heterojunction solar cells with Si/Si1-xGex quantum wells

Heterojunction with intrinsic thin-layer (HIT) solar cells attract attention due to their high open circuit voltage and stable performance. However, short circuit current density is difficult to improve due to light losses of transparent conductive oxide and hydrogenated amorphous silicon passivation (a-Si:H) layer and low absorption coefficient of crystalline silicon (c-Si). Silicon germanium alloy (Si/Si1-xGex) quantum wells and quantum dots are capable of improving low light utilization by strong optical absorption in the infrared region. In this article, opto-MoS2of the HIT solar cells integrated with Si/Si1-xGex quantum wells (HIT-QW) as a surface absorber are investigated by numerical simulation with Technology Computer Aided Design (TCAD). The influences of germanium content on the MoS2of HIT solar cells with long carrier lifetimes of Si1-xGex layers (p*) and defect-free a-Si:H/c-Si interface are investigated at first. The simulation results indicate that optical utilization in the infrared region is enhanced with the increase of germanium fraction, while open circuit voltage degrades due to the decreasing of the energy band gap of Si1-xGex, radiative recombination and auger recombination mechanism in the Si/Si1-xGex quantum wells. And the conversion efficiency reaches a maximum value at a germanium fraction of 0.25 then drops distinctly. When the germanium fraction increases from 0 to 0.25, the short circuit current density increases from 34.3 mA/cm2 to 34.8 mA/cm2, while the open circuit voltage declines from 749 mV to 733 mV. Hence, the conversion efficiency increases from 21.5% to 21.7% due to the fact that the enhancement of short circuit current density compensates for the reduction of open circuit voltage. When the germanium content increases to more than 50%, a serious open circuit voltage loss of more than 130 mV associated with the energy band gap loss of Si1-xGex arises in the HIT-QW solar cells, which indicates that the dominating carrier transport mechanism changes from shockley diffusion to recombination in the Si/Si1-xGex quantum wells. Subsequently, the influences of interface defects at a-Si:H/c-Si interface and bulk recombination centers in the Si/Si1-xGex quantum wells are discussed. Both interface holes at a-Si:H/c-Si interface and bulk holes in Si1-xGex quantum wells can be recombined through the interface defects at a-Si:H/c-Si interface and bulk recombination centers in the Si/Si1-xGex quantum wells, respectively, which restricts the position of hole fermi level in the open circuit condition. When the germanium fraction increases, the influence of interface defects at a-Si:H/c-Si interface becomes weak on the degradation of open circuit voltage compared with the significant influence of the bulk trap centers. Moreover, p* of longer than 510-5 s is necessary for the retention of electrical performance of HIT-QW solar cells by the simulation. Based on this research, high-efficiency HIT solar cells can be achieved by incorporating high-quality Si/Si0.75Ge0.25 quantum wells, which also requires the impactful passivation of a-Si:H/c-Si interface.

Analytical study of a-Si:H/c-Si thin heterojunction solar cells with back surface field

In this paper, the high efficiency TCO-n(aSi:H)-i(aSi:H)-p(c-Si)-$$\hbox {p}^{+}$$p+(aSi:H) heterojunction with intrinsic thin-layer (HIT) solar cell is analyzed. The effects of the intrinsic thin-layer and the back surface field (BSF) on the photovoltaic parameters of thin solar cells are discussed. The analytical results show that the intrinsic layer inserted at the a-Si:H/c-Si interface decreases the density of interface states. If the interface state density is lower than $$10^{11}\,\hbox {cm}^{-2}$$1011cm-2 in the presence of an intrinsic thin layer a-Si:H, the effect of recombination current density on the photovoltaic parameters becomes low. The BSF formed by hydrogenated amorphous silicon layer can increase the conversion efficiency by about 2.6 % and the open-circuit voltage to $$\sim $$~80 mV as compared to the HIT solar cell wherein the BSF is realized by crystalline silicon. The results obtained from the simulation studies are in good agreement with the literature, and might open promising opportunities for enhancing the design parameters of HIT cells.

Development of Selective Electroless‐Deposited Electrode in Heterojunction with Intrinsic Thin‐Layer Solar Cell

AbstractIn this paper, we describe selective deposition of a major electrode and a protection electrode in a heterojunction with intrinsic thin‐layer (HIT) type solar cell. Sn and Ni were used for the protection electrode to prevent the oxidation of Cu, which was used for the main electrode. SEM and TEM were used to analyze the microstructural evolution and changes in the interface as a result of each electroless deposition. Finally, the performance of our solar cell created via electroless deposition was evaluated. We determined the photovoltaic conversion efficiency (PCE) to be 16.4 %, the fill factor (FF) to be 72.2 %, the open circuit voltage (Voc) to be 681 mV, and the short circuit current (Jsc) to be 33.0 mA/cm2. These output values match the performance of an Ag screen‐printed solar cell and demonstrate the possibility of commercializing an inexpensive HIT solar cell with high efficiency.

Analysis of the possibility of high-efficiency photovoltaic conversion in tandem heterojunction thin-layer solar cells

The possibility of creating tandem heterojunction-with-intrinsic-thin-layer (HIT) solar cells possessing photovoltaic conversion efficiency greater than that of the best existing single-junction HIT structures is analyzed. It is established that, because of small carrier lifetimes and high degrees of compensation, the use of amorphous silicon in tandem HIT cells cannot provide for record high conversion efficiency. Key parameters of the material for a widegap p-n junction on the frontal side of tandem solar cells are determined that will allow a photovoltaic conversion efficiency above 25% under AM1.5 conditions to be reached.