HIT Solar Cells Research Articles

An investigation of the impact of nafion polymer on surface passivation and analysis of degradation in HIT solar cells for improvement performance

The effectiveness of Heterojunction with an intrinsic thin layer (HIT) solar cell is greatly improved by using Nafion polymer to passivate the surface and reduce carrier recombination processes. The enhancement of high-efficiency solar cells has garnered considerable interest in surface passivation as a potential substitute due to their exceptional electrical properties. There is little research on the optical and electrical characteristics of different levels of Nafion concentration. The HIT solar cells were treated with varying Nafion-passivation concentrations (2.5 wt %, 5 wt %, 10 wt %). The most significant performance improvement is at a concentration of 2.5 wt% after degradation for 8 h. The open-circuit voltage (Voc) climbed to 735.05 mV, and the fill factor (FF) increased at + 3.49 %, followed by the increase of power conversion energy (PCE) at + 0.96 %, both showing a considerable increase compared to a cell made from an unaffected cell. Due to its ability to boost silicon solar cell performance, a low Nafion concentration is preferred.

Exploring the potential of tin-based perovskite-silicon tandem solar cells through numerical analysis: A pathway to sustainable energy innovation

“Necessity is the mother of invention.” The global imperative to transition from fossil fuels to renewable energy sources, driven by the pressing issue of climate change, highlights the significance of advancing solar energy technologies. While single junction solar cells have reached a peak efficiency of approximately 31 %, the pursuit of higher efficiency has led to the exploration of tandem solar cell architectures, including perovskite-silicon and all-perovskite configurations. However, the widespread use of lead in perovskite structures raises environmental and health concerns. In response to these challenges, this study proposes a novel approach by integrating a tin-based wide bandgap absorber layer with a silicon HIT solar cell (Heterojunction with Intrinsic Layer). The investigation consists of an extensive exploration of six different carrier transport layers (CTL) for the top perovskite layer, considering variations in thickness and defect density. A comprehensive analysis of charge carrier dynamics within the device is conducted to understand the role of defect density in influencing solar cell performance parameters. Simulation results show that the overall tandem device gives an encouraging PCE of 32.12 % in 2 T configuration due to its excellent high value of current density matching 17.63 mA/cm2 and open-circuit voltage of 2.19V. We sincerely hope that our work will open new avenues in the field of Solar Photovoltaics paving the way for future innovations.

New optimized HIT solar cell using wide-bandgap nc-3C-SiC:H as a window layer

This study focuses on the investigation of HIT solar cell using nanocrystalline hydrogenated cubic silicon carbide (nc-3C-SiC:H) as a window layer. The selection of nc-3C-SiC:H is motivated by its wide bandgap, high electron drift velocity, and exceptional optical, electrical, and structural properties. Employing SCAPS-1D simulator, a comprehensive simulation analysis of thin nc-3C-SiC:H-based solar cell was conducted. By analyzing the current–voltage and quantum efficiency curves, the impact of doping concentration in the window layer was examined, covering a range from [Formula: see text] to [Formula: see text]. A rapid degradation of [Formula: see text] was observed for high doping concentrations. Additionally, the temperature dependence of external DC parameters for the temperatures 273, 300, and 318[Formula: see text]K was explored under AM1.5G and AM1.5D sunlight spectra. The application of two distinct light spectra resulted in the DC parameters exhibiting minimal variation or similarity. The study also took into account the influence of window thickness variation, temperature, and doping concentration. The findings demonstrate a remarkable influence of temperature and doping concentration on the DC parameters. [Formula: see text] value of 30.29[Formula: see text]mA/cm2 was achieved with a 3-nm thickness and an optimal efficiency of 19.48% was registered with a doping concentration of up to [Formula: see text], showcasing the promising potential of nc-3C-SiC:H.

Simulation studies on MoS2 (n)/a-Si:H (i)/c-Si (p)/MoO3 heterojunction solar cells using one sided short diode approximation

C-Si based heterojunction solar cells with dopant-free electron and hole transport layers (ETL and HTL) have attracted the researcher’s attention due to their high efficiency and relatively less complicated fabrication process. A number of materials have been proposed for their applications, as ETL and HTL. We have chosen n-type MoS2 monolayer as ETLfor c-Si based heterojunction solar cells and optimized the layer parameters, doping and thickness to achieve the efficiency of 21.05% with a Voc of 641 mV and Jsc of 45.88 mA/cm2 when direct metallization of Ag is used at back contact using one sided short diode approximation. Further, withinsertion of MoO3 as HTL at the back before Ag electrode, the efficiency could be improved to 23.54%with proper tuning of work function of MoO3. The increase in efficiency is accompanied with a small increase in Voc (650 mV) and Jsc (46.5 mA/cm2). Our studies provide a pathway to fabricate dopant free c-Si based heterojunction solar cells with comparable efficiency as those for HIT solar cells.

Potential application of novel graphene/diamane interface in silicon-based heterojunction with intrinsic thin layer solar cell

In this article, the patentability of novel graphene/diamane interface in HIT solar cell has been explored by simulated a structure modelled as: graphene (TCO) / n-diamane / a-Si: H (i) / p-cSi / Ag (back contact) with the help of software AFORS-HET version 2.5. Here, n-type diamane is used as an emitter layer and graphene as TCO. An efficiency of 31.2 % is achieved with this structure by varying various parameters of n-type diamane, p-crystalline silicon and hydrogenated intrinsic amorphous silicon layer which is pressed in between the two oppositely doped wafer (diamane and c-Si). Furthermore, when ITO is used as TCO then a comparatively low efficiency 27.15 % is achieved and when the commercially available values of silicon’s parameters is used for the validation of results then an efficiency of 24.15 % is obtained. Some parameters of a-Si: H (i) has been further optimized and the optimum efficiency 31.2 % has been found at minimum thickness of 3 nm at bandgap 1.6 eV. Finally, we have demonstrated that only carbon material has an ability that its two-dimensional allotropes can be used as an emitter layer as well as efficient transparent conducting electrode.

Emitter layer optimization in heterojunction bifacial silicon solar cells

Silicon solar cells continue to dominate the market, due to the abundance of silicon and their acceptable efficiency. The heterojunction with intrinsic thin layer (HIT) structure is now the dominant technology. Increasing the efficiency of these cells could expand the development choices for HIT solar cells. We presented a detailed investigation of the emitter a-Si:H(n) layer of a p-type bifacial HIT solar cell in terms of characteristic parameters which include layer doping concentration, thickness, band gap width, electron affinity, hole mobility, and so on. Solar cell composition: (ZnO/nc-Si:H(n)/a-Si:H(i)/c-Si(p)/a-Si:H(i)/nc-Si:H(p)/ZnO). The results reveal optimal values for the investigated parameters, for which the highest computed efficiency is 26.45% when lighted from the top only and 21.21% when illuminated from the back only.

Hydrogen effect on structural and optical properties of in-situ fabricated nc-Si:H prepared by facing targets sputtering

We report high-quality hydrogenated nanocrystalline silicon (nc-Si:H) thin films were prepared by facing targets sputtering (FTS) in the environment of Ar and H2 mixture gases. By increasing hydrogen dilution (RH) of FTS deposition, the structural evolution of as-fabricated Si-based films was observed. Fourier infrared spectroscopy (FTIR) shows that decrease in bonded hydrogen (CH) concentration, especially that of (Si-H2)n with increasing RH, indicating that the H etching effect increased atomic density of these films, thus improving film quality. With the RH increased, the Raman spectra show that the morphological transition from amorphous to crystalline states. We further reveal correlations between the degree of structural order in the amorphous network and the RH by calculating experimental data from the Raman measurements. Moreover, as-fabricated nc-Si:H films show large bandgap and narrow band tail states with increasing RH, which allows potential applications in the window passivation layer for HIT solar cells and Si-based charge-coupled devices (CCD). This work offers a novel route to fabricate high-quality nc-Si:H films for optoelectronic applications.

Investigation of HIT solar cells low frequency noise characteristics

The effect of solar cell fragment annealing on its noise characteristics is shown. The calculated difference in relaxation times arising from the change in noise after annealing was 30%. Measurements of noise characteristics in the dark and under illumination with a red laser with different radiation power were carried out. Close to linear dependences of noise power reduction with increasing radiation power were obtained.

Influence of the properties of p-a-Si:H layer and the work function of front contact on silicon heterojunction solar cell performance

Heterojunction c-Si and hydrogenated amorphous silicon (a-Si:H) devices with intrinsic a-Si:H thin layer, known as HIT solar cells, are promising alternatives to conventional c-Si solar cells for the possibility of higher open circuit voltage, low temperature processing and lower costs. We have studied the influence of the properties of p-a-Si:H layer and the work function of the front electrode material on the performance parameters of n-c-Si based HIT solar cells using numerical simulation. The findings are further analyzed using energy band diagrams and carrier concentration profiles at the heterointerface of a-Si:H/n-c-Si to reveal the underlying charge transport mechanisms.

Numerical Simulation for Optimization of Ultra-thin n-type AZO and TiO2 Based Textured p-type c-Si Heterojunction Solar Cells

A maximum efficiency of 17 % for ultra-thin n-type AZO layer and 17.5 % for ultra-thin n-type TiO2 layer based silicon heterojunction solar cell is reported by optimizing its properties which is much higher than practically obtained efficiency signifying a lot of improvements can be performed to improve efficiency of TiO2/Si and AZO/Si heterojunction solar cell. AZO layer and TiO2 layer is used as n-type emitter layer and crystalline silicon wafer is used as p-type (p-cSi) layer for modelling AZO/Si and TiO2/Si heterojunctions solar cell respectively using AFORS HET automat simulation software. Various parameters like thickness of AZO, TiO2 layer, p-cSi layer, doping concentration of donors (Nd) and effective conduction band density (Nc) are optimized. Finally, texturing at different angle is studied and maximum efficiency is reported at 70 μm thick p-type crystalline Silicon (p-cSi) wafer, that can be very helpful for manufacturing low cost HJ solar cells at industrial scale because of thin wafer and removal of additional processing setup required for deposition of amorphous silicon i-layer. Utilization of TiO2 and Aluminium doped Zinc Oxide as n-type layer and p-cSi as p-type layer can help in producing low cost and efficient heterojunction (HJ) than compared to HJ with intrinsic thin layer HIT solar cells.

Simulation and Optimization of Back Surface Field for Efficient HIT Solar Cells

We investigate an appropriate material for the optimisation of Back Surface Field (BSF) layer in Heterojunction with Intrinsic thin layer (HIT) solar cells: ITO/p-a-Si:H/i-a-Si:H/n-c-Si/BSF/Ag. The obtained results show that it is important to choose hydrogenated amorphous silicon to create the BSF layer instead of crystalline silicon as in the case for conventional HIT solar cells. The use of hydrogenated amorphous silicon creates a significant band discontinuity at the valence band due to the presence of the heterojunction at the interface n-c-Si/n++-a-Si:H. We also show that increasing the BSF layer thickness degrades the solar cell J-V characteristic due to the low diffusion length and lifetime of the minority carriers and also because of the increase of the recombination rate in this heavily doped layer. The global device optimization was performed with SCAPS–1D software under STC conditions and the results show that a considerable efficiency of 27.44 % can be achieved.

Surface Passivation Studies of n-type Crystalline Silicon for HIT Solar Cells

Surface passivation of n-type Crystalline Silicon wafer using thin dielectric films is an important and major factor in improving photovoltaic performance of HIT solar cells. In this study, Numerical simulation was carried out by using AFORS-HET simulation software in which energy band diagram with and without surface passivation (a-Si:H(i)) was investigated and the highest conduction band offset obtained on n type c-Si wafer is 0.85 eV which is comparatively higher than p-type c-Si wafer which was reported between 0.1 and 0.15 eV. Performance of HIT solar cell with passivation layer is simulated and obtained efficiency of 12.9% by incorporating actual conditions to compare with experimentally obtained data. It has been understood that applying an effective dielectric passivation of silicon surface resulted with high open circuit voltage (Voc) and low surface recombination lead to an increase of cell efficiency by 1.1% (from 11.8 to 12.9%). Also, the simulated results shows that to obtain good conversion efficiency Defect density of interface (Dit) should be lower than 1x1011 cm−2eV−1. Validation of the simulation results is done by conducting PECVD experiments for optimizing the amorphous silicon passivation to a layer thickness down to 15 nm. HIT Solar cells have been developed, using the optimum layer of passivation, and their performance have been studied. An improvement in the minority charge carrier lifetime of ~53 µs (from 215 to 268 μs) and on the other hand reduction in the surface recombination velocity of ~ 12.9 cm/s (from 65.11 cm/s down to 52.23 cm/s) has been achieved through passivation which effectively increased the open circuit voltage (Voc) from 0.690 to 0.705 V. In this preliminary study, a conversion efficiency of 11.3% of heterojunction with intrinsic thin layer (HIT) solar cell on 10 mm × 10 mm n-c-Si wafer has been obtained.

Characterization of the Laser Scribing Process of HIT Cells for a Photovoltaic Shingled Module

Shingled string technology can be used to maximize the output power of photovoltaic modules. The maximum power (Pmax) of a shingled photovoltaic module can be increased by using a bifacial heterojunction with an intrinsic thin layer (HIT) of cells. To fabricate the shingled strings for a high power module, we first cut 6-inch solar cells by laser scribing while minimizing cutting loss. Unlike standard crystalline silicon (c-Si) solar cells, the structure of bifacial HIT solar cells is weak under thermal effect, so an optimal scribing condition had to be found. After laser scribing processes had been optimized, Pmax was increased by 0.02W for each separated solar cells when we using an ultraviolet (UV) laser compared to the green laser, and a UV cut shingled string of HIT cell was demonstrated for the first time.

Investigation of the interface defect density at pm-Si:H/c-Si and the surface recombination speeds on silicon heterojunction solar cells

We carefully analyze in this article, the influence of the interface defect density of the defective surface between crystalline silicon and hydrogenated polymorphous silicon (i-pm-Si:H/n-c-Si) on the current density-voltage (J–V) characteristic of n-type HIT solar cells (ITO/p-a-SiC:H/i-pm-Si:H/n-c-Si/Al). We have also studied the variation of the electrons and holes surface recombination speeds on the front and the back face of the studied cell. The results show that the recombination rate is higher on the front surface of the c-Si wafer when the defect density increases. Indeed, we have found that for the two values of the front contact barrier height at the ITO/p-a-SiC:H, when the interface defect density increases, the Voc and the FF drop. Thus, the efficiency goes from almost 20 to 2 %. These results allow us to conclude that to have a good Voc, the surface of the active layer should be passivated to have a interface defect density less than 1011 cm−2. For the variation of the surface recombination speed SnL with the interface defect density for electrons at the back face of the solar cell, no sensitivity is observed. For small values of these defects, the efficiency increases when the holes surface recombination speed SpL is decreased, but for large values of interface defect density, no improvement is observed, even for low surface recombination speeds.

The prospective application of a graphene/MoS2 heterostructure in Si-HIT solar cells for higher efficiency.

The efficiency of a Si-HIT (heterojunction with intrinsic thin layer) solar cell based on a graphene/MoS2 heterostructure has been optimized by varying the various parameters of graphene (Gr) as a transparent conducting electrode (TCE) and n-type molybdenum disulfide (n-MoS2) as an emitter layer. The photovoltaic performance of a graphene/n-MoS2/a-Si:H/p-cSi/Au single facial HIT solar cell has been studied using AFORS-HET v2.5 simulation software. A maximum output efficiency of 25.61% has been achieved. The obtained results were compared with the results from a commercially available a-Si:H layer and p-cSi wafer after simulation. Moreover, the dependence of the cell performance on changes in the TCE and the back contact materials has also been studied. Finally, it has been demonstrated that the graphene layer and n-MoS2 layer could act as a TCE and an efficient emitter layer, respectively, in a n-MoS2/p-cSi based HIT solar cell.

High-efficiency Crystalline Silicon Solar Cells: A Review

Solar energy is a clean renewable energy resource that can be converted to electricity with photovoltaic (PV) technology without environmental damage. Solar energy can be transformed to electricity using a range of technologies, but crystalline silicon (c-Si)-based PV technology dominates in the PV market due to the high efficiency, long-term stability, reliability, and second most abundant (27%) material. Recently, c-Si solar cells achieved an outstanding efficiency of 26.7% through silicon heterojunction technology combined with an interdigitated back contact structure. Most industries and researchers are attempting to improve the efficiency further to reach the silicon limit. The dominant position of crystalline silicon solar cell in large-area electricity production and industrialization motivated us to write this review paper. This review paper covers the key factors that affect the efficiency, such as structure, process optimization, cost reduction strategies. In addition, some promising cell structures, such as PERC, IBC, HIT, and HBC solar cell, and their efficiencies are reported. Overall, this study provides a detailed idea to the new photovoltaic researchers regarding the solar cell structure, their efficiencies, and future potential of solar cells.

Comparative investigation of performances for HIT-PV and PVT systems

Crystalline silicon heterojunction solar cells are a promising candidate for high efficiency solar cells, and the heterojunction photovoltaic (HIT-PV) module is strongly dependent on the temperature. In this study, we design three heterojunction photovoltaic modules to improve the performance by preventing from over-heating, with, glass, Tedlar/Polyethylene terephthalate/Tedlar (TPT) and aluminum substrates, respectively. The efficiencies of those HIT-PV modules are investigated under four different outdoor climates. The aluminum-module shows the best thermal dissipation; while the glass-module/TPT-module have the better electrical efficiency and electrical energy, since there is the high reflectivity layer on the surface of the glass (and TPT) substrates rather than the aluminum substrate. In order to increase the output power of HIT-PV modules, we design a heterojunction photovoltaic thermal (HIT-PVT) system based on HIT solar cells and aluminum thermal collector. The measured results of HIT-PVT system show that the coolant circulation increase the output power, and the HIT-PVT module can provide the domestic hot water supply (up to 51.2 °C) under outdoor conditions. In addition, the cost of HIT-PVT systems are much lower than those of the conventional photovoltaic systems, and the investment payback time can be less than 3 years.

Damage to passivation contact in silicon heterojunction solar cells by ITO sputtering under various plasma excitation modes

Analysis of damage to passivation contact in heterojunction with intrinsic thin layer (HIT) solar cells by indium tin oxide (ITO) sputtering under various plasma excitation modes such as radio frequency (RF), direct current (DC), RF-superimposed DC, pulsed DC is presented. A significant degradation of effective minority carrier lifetime of the precursor cells at both low and high-level injections after the ITO deposition by sputtering technique was observed regardless of plasma excitation modes. We found that the main reason for this degradation was mainly due to the ion flux in the sputtering plasma rather than the ion kinetic energy. On the basis of the experimental and simulated results, we attributed the degradation of surface passivation quality mainly to the damage of the amorphous-silicon/crystalline-silicon interfaces rather than that of the intrinsic hydrogenated amorphous silicon layers. This degradation could be significantly reduced by the ITO deposition at a high temperature in which a trade-off between degradation and curing step was expected to occur. The cell performance of the HIT solar cells using the ITO films deposited by various plasma excitation modes at 180 °C was subsequently discussed. The ITO films deposited by the RF-superimposed DC mode exhibited a high potential as excellent opto-electrical properties and free sputter-induced damage electrodes for HIT solar cell applications. To our best knowledge, this is the first time that the ITO films deposited by the RF-superimpose DC mode are used as electrodes in the HIT solar cells.

Review of ZnO Transparent Conducting Oxides for solar applications

Solar energy is a renewable clean energy and photovoltaic is one of the most effective ways to use sunlight currently. Transparent conductive films such as ITO, AZO and so on as the window layer are widely used in HIT and other high efficientcy silicon-based heterojunction solar cells. The Zinc oxide conductive thin film (ZnO) has a high transmittance at 800-1200 nm and a low resistivity, and has the potential to replace ITO film. However, it is limited by the preparation method. The resistivity of the film itself is very high, about 1E-3Ω⋅ cm. And the average optical transmittance in the 300-1200 nm wavelength range is less than 80%. Furnace annealing can play a key role in the elimination of stress, film of repair, recrystallization and grain growth, reducing the interface defects, improving the interface properties, and film photoelectric performance is improved. In the other hand, doping is necessary for achieve a high properties ZnO film.

Deposition and characterization of ITO thin film over glass for defogger application and for solar photovoltaics

Indium thin oxide (ITO) films have been used in solar cell applications as top conducting layers for many years. These films possess very good transmission and a low sheet resistance thus making them ideal candidate material for top conducting layers in thin film and HIT solar cells. In the present work, ITO films have been deposited over soda lime glass substrates for use as defogger applications, and for use as front contact electrode in HIT type solar cells as well. ITO deposition is done using pulsed DC sputtering technique inside a vacuum chamber with large size ITO sputtering target of 15 inches by 5 inches. Silver bus bars are printed at the two edges of glass using thick film screen printing technique and the firing of thick film is done in a belt furnace. The deposited ITO thin film characterization is done by using XRD, SEM and 4 probe sheet resistance measurement techniques. The transmission spectra is analyzed for optical transmission properties.