Intrinsic Thin Layer Solar Cells Research Articles

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.

Electrical and Optical Characterization of Non-Hydrogenated a-Si/c-Si Heterojunction Solar Cells

This work deals with the performance of a heterojunction with intrinsic thin layer solar cell by sputtering silicon on p-type crystalline silicon substrate in argon ambient without hydrogen addition. This first effort was an attempt to use cost-effective means to convert light into electricity and to find fabrication processes which use fewer and cheaper materials for the fabrication of solar cells. Since transport mechanisms of amorphous silicon/crystalline silicon heterojunctions are still under investigation, the aim is to examine the behavior of the fabricated samples under electrical and optical constraints. Initial cell characterization includes electrical behavior via current-voltage characteristics and optical investigation via reflectance and absorptance measurements. Results are analyzed in a tentative to follow the absorption, generation and collection processes in the fabricated cell. The heterojunction interface is found to be a limiting factor in the cell performance. Under sun illumination, the open circuit voltage was 140 mV, the short circuit current was of 6 µA and the fill factor was of 42.56 %. Dark current-voltage characteristics indicated a tunneling and/or recombination carrier transport mechanism, while aborptance/reflectance measurements showed a generation process occurring in most in the crystalline silicon-side of the amorphous/crystalline silicon heterojunction. A carrier collection limitation is a very probable origin of the decreased cell generated current.

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.

In-Sn Oxide Bilayer Transparent Conductive Film by DC Magnetron Sputtering for Silicon Heterojunction Solar Cells

The optical and electrical properties of the front transparent conductive film of a heterojunction with intrinsic thin-layer solar cell are the key factors that determine the photovoltaic conversion efficiency of the device. First, the relationship between the structure as well as optoelectronic properties and sputtering process of ITO-97/3 (In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> :SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 97 wt.%:3 wt.%) thin film with low SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> content and conventional ITO-90/10 (In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> :SnO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> = 90 wt.%:10 wt.%) thin film was compared and studied in this article. Next, the application of ITO-97/3 thin film for heterojunction with intrinsic thin-layer solar cells was verified. It was found that, although the spectral response was improved, the series resistance of the device deteriorated. Finally, the bilayer structure of ITO-90/10 and ITO-97/3 was introduced into a heterojunction with intrinsic thin-layer solar cell. The results showed that the overall performance of the device was improved because of the combination of electrical and optical characteristics of the bilayer.

A Method for Calculating Operating Characteristics of Silicon Heterojunction Solar Cells with Arbitrary Parameters of Crystalline Substrates

Specific features of the current processes in silicon heterojunction with intrinsic thin layer solar cells have been investigated. The proposed model takes into account the ambipolar motion of carriers and allows one to calculate the operating characteristics at an arbitrary ratio of the diffusion length and the crystalline-substrate thickness. A numerical method for estimating the recombination-loss rate on silicon wafer surfaces based on the comparative analysis of the experimental values of short-circuit current and open-circuit voltage is described.

Enhanced electrical performance for heterojunction with intrinsic thin-layer solar cells based photovoltaic thermal system with aluminum collector

Crystalline silicon heterojunction with intrinsic thin-layer photovoltaic (HIT-PV) module produces more output power, compared with the c-Si photovoltaic module. However, it presents a risk of overheating in hot weather. In this paper, we used a new cooling design of the heterojunction with intrinsic thin-layer photovoltaic thermal (HIT-PVT) module to lower the temperature using laminated encapsulation of an aluminum collector in outdoor climates. The measured electrical, thermal and total efficiencies of a HIT-PVT system can catch up to 17.47%, 34.71% and 52.18%, respectively. Moreover, comparing with HIT-PV module, the output power of the HIT-PVT module was enhanced by 5.58% with coolant circulation, and the converted electrical energy can be increased by 9.81% with the designed HIT-PVT module. In addition, the primary energy savings of the new HIT-PVT and HIT-PV systems were 79.77% and 43.71%, respectively.

Low temperature defect passivation technology for semiconductor electronic devices—supercritical fluids treatment process

Currently, defects existing in materials and at the interface are the main bottlenecks limiting the manufacture of high-performance electron devices, especially semiconductor devices where the performance and reliability are affected by these defects. Therefore, high temperature annealing (HTA) is often applied to passivate defects, though it raises additional issues in the device fabrication process, such as heat budget and impurity diffusion. In this article, we propose a passivation technique induced by a supercritical fluid (SCF) treatment at relative low temperatures and test it for use in various devices. The SCF treatment is equipped with both high permeability and solubility to introduce reactive substances which act to passivate defects and further enhance device performance without altering the device material or making major changes to the fabrication process. The experimental results prove that this technique can be applied to the AlGaN-based ultraviolet C light-emitting diode to increase the band-to-band emission spectrum of 280 nm, as compared with the 360 nm emission spectrum of defects. The electrical characteristics of the GaN-based high electron mobility transistor including on/off currents, trans-conductance (Gm), and current collapse were also improved. Such a SCF treatment can also be applied to Si-based fin field effect transistors to increase the Gm and mobility because of reduction of defect concentration. This SCF treatment was also applied to a current-production heterojunction with intrinsic thin layer solar cell to improve the efficiency from 18.2% to 19.5%. Using this SCF treatment on InGaZnO thin film transistors results in effective suppression of the VTH shift, which proves the defects in the gate insulator have been eliminated. The SCF treatment has also been applied to a SnO2 gas sensor to increase the selectivity and endurance to humidity because of the passivation of vacancies. These all confirm that this SCF treatment's passivation capability can be applied to various electron devices. In addition, this SCF treatment has the advantages of being performed at low-temperature in a non-destructive process in a batch treatment with high selectivity, which provides the semiconductor industry a method to solve the manufacturing bottleneck in advanced electron devices.

Benefits of photonic management strategy for highly efficient bifacial solar cells

Bifacial solar cells have received great attention due to their higher power generation capacity compared to monofacial solar cells. However, insufficient infrared absorption becomes an obstacle to enhance the performance of bifacial solar cells. In this work, the distributed Bragg reflector (DBR), which is one of the most promising photonic management strategies, is innovatively applied to the backside of bifacial solar cells to improve the light absorption for long wavelengths (950–1100 nm). Through the application of MgF2/TiO2 DBR at the rear side of bifacial solar cells, infrared absorption is enhanced for solar cells with different backside pyramid angles and wafer thickness. Experimental results suggest 20 degrees is the most effective backside pyramid angle for the enhancement of infrared absorption. With this DBR reflector, the infrared energy loss is also sharply reduced for thinner wafers. The improvement of the short-circuit current for two typical bifacial solar cells (the passivated emitter and rear cell and the heterojunction with intrinsic thin-layer solar cell) further verify the absorption enhancement through the management of this backside photonic crystal. Our work demonstrates that the DBR technology is a promising candidate for more efficient bifacial solar cells.

Atomic simulation of Si&lt;sub&gt;&lt;i&gt;y&lt;/i&gt;&lt;/sub&gt;H&lt;sub&gt;&lt;i&gt;x&lt;/i&gt;&lt;/sub&gt; structure configuration in a-Si:H thin films

The hydrogenated amorphous silicon (a-Si:H) film is the core structure of hetero junction with intrinsic thin layer solar cell. Its quality determinates the photoelectric conversion efficiency of this solar cell directly. The configuration of Si&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;H&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; is an important structure characteristic of a-Si:H films, and it can influence on the quality of a-Si:H thin films and their application properties. However, it is difficult to study them in depth and detail by the existing analytical and testing methods. In this paper, the structure configuration of Si&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;H&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; in a-Si:H /c-Si thin films and the effect of substrate temperature on its content have been simulated and analyzed by molecular dynamics method. A modified Tersoff potential developed by Murty was used to calculate the inter-atomic forces. The results showed that the Si&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;H&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; structure in a-Si:H thin films can be summarized into six configurations. Three traditional configurations, including SiH, SiH&lt;sub&gt;2&lt;/sub&gt; and SiH&lt;sub&gt;3&lt;/sub&gt;, can be referred to as SiH&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; configurations.The other three nove configurations, including HSi&lt;sub&gt;2&lt;/sub&gt;(s), HSi&lt;sub&gt;2&lt;/sub&gt;(l) and HSi&lt;sub&gt;3&lt;/sub&gt;, can be referred to as HSi&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt; configurations. The main differences between the configurations of HSi&lt;sub&gt;2&lt;/sub&gt;(l) and HSi&lt;sub&gt;2&lt;/sub&gt;(s) are the longer Si—H bonds and bigger bond angle in HSi&lt;sub&gt;2&lt;/sub&gt;(l) configuration than those in HSi&lt;sub&gt;2&lt;/sub&gt;(s) configuration. All of the Si-H bonds in SiH&lt;i&gt;&lt;sub&gt;x&lt;/sub&gt;&lt;/i&gt; configurations are strong chemical bonds, while the Si—H bonds in HSi&lt;sub&gt;y&lt;/sub&gt;configurations are weak physical bonds. The further calculations of the Si-H bond energies in six configurations have been carried out by the first principle method. According the bond energies results, we can deduce that the order of the stability of six configurations from high to low is SiH &gt; SiH&lt;sub&gt;2&lt;/sub&gt; &gt; SiH&lt;sub&gt;3&lt;/sub&gt; &gt; HSi&lt;sub&gt;2&lt;/sub&gt;(s) &gt; HSi&lt;sub&gt;2&lt;/sub&gt;(l) &gt; HSi&lt;sub&gt;3&lt;/sub&gt;. Comparing the Si—H bond energies of the six configurations with the solar energy, it is found that the Si-H bond energy in HSi&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt; configuration is in the range of visible and infrared light in solar light. Si—H physical bonds are easy to fracture in HSi&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt; configuration caused by solar light. This may be the main mechanism of producing Steabler-Wronski (S-W) effect in amorphous silicon thin film cells. In addition, the rise of substrate temperature in the deposition process of a-Si:H films will lead to a significant decrease in the configuration content of all kinds of Si&lt;i&gt;&lt;sub&gt;y&lt;/sub&gt;&lt;/i&gt;H&lt;sub&gt;&lt;i&gt;x&lt;/i&gt; &lt;/sub&gt;configurations.

Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing

In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

Numerical Study of TCO/Silicon Solar Cells with Novel Back Surface Field

ZnS/Si/CuO heterostructure is investigated by a theoretical approach as a possible low-cost design for photovoltaic conversion in the track of the heterojunction with intrinsic thin layer solar cells. Our results indicate that, owing to perfect electron affinity and lattice matching properties, zinc sulfide with adequate Al doping can efficiently replace zinc oxide window layer as an emitter region for silicon-based solar cells. Lattice mismatch, energy band alignment at the interfaces and material resistivity are the framework parameters of the study. By focusing on the open circuit voltage parameter, the back metal/Si and silicon base doping were optimized so that the conversion efficiency was increased from 3.37% to 15.19%. The introduction of a cupric oxide (CuO) layer acting as a p + back surface field with a bandgap of 1.35 eV and appropriate doping as high as 7 × 1018 cm−3 can enhance the conversion efficiency to 17.30%, provided that the silicon material remains free from contamination by copper atoms and also by performing a suitable treatment of CuO to lower its resistivity.

Amorphous layers by electron beam evaporator deposition for hetero-junction with intrinsic thin layer solar cells applications

A low-cost process with electron beam evaporator deposition for amorphous layers was demonstrated in hetero-junction with intrinsic thin layer (HIT) solar cell. The cleaning process with saw damage removal procedure and the annealing temperature are also discussed in this work. The open-circuit voltage (Voc) and short-circuit current density (Jsc) were obtained as 285 mV and 2.9 mA/cm², respectively, with 5 min saw damage removal and 450°C forming gas annealing. Therefore, the low-cost process with the electron beam evaporator deposition could possibly fabricate the HIT solar cell and be a candidate for future higher performance photovoltaic device with optimisation process condition.

Study of Au/n-Ti&lt;sub&gt;2&lt;/sub&gt;S/p-Si/Al Schottky-Type Thin Film Heterojunction Solar Cells: Computer Simulation Modeling

The Au/n-Ti2S/p-Si/Al heterojunction with intrinsic thin-layer solar cells were analyzed by AFORS-HET software program. Thickness of the emitter intrinsic layer and the interface state density of such cells were studied. In which, the intrinsic layer inserted between the Ti2S and crystalline p-type silicon substrate, reduce the interface state density. The thinner intrinsic layer is better than thicker one, when the interface state density is lower than 1010 cm-2.V-1. As the thickness of the emitter increased, both short-current density (J) and the conversion efficiency were decreased. The dependence of J-V characteristics of the Au/n-Ti2S/p-Si/Al heterojunction solar cell on Front and back Surface Recombination Velocity (SRV) was studied. By optimizing the initial parameters set, the Au/n-Ti2S/p-Si/Al solar cell reaches a high efficiency (I·) up to 21.849% (FF: 0.834, Voc: 0.666 V, Jsc: 39.39 mA/cm2).

Study of p-Layer Doping Density and Surface Band Bending on the Indium Tin Oxide/Hydrogenated Amorphous Silicon Heterojunction Solar Cells

A solar cell (indium tin oxide (ITO)/p-doped amorphous silicon (p-a-Si:H)/intrinsic polymorphous silicon (i-pm-Si:H)/n-doped crystalline silicon (n-c-Si)) simulation, focused on p-layer doping density NA and surface band bending Esbb at the interface ITO/p-layer has been performed. Despite the deterioration of p-layer material quality with doping density, the reduced bulk recombination was found to compensate for the increased loss in the p-layer. An increase of p-layer doping density NA and contact barrier height φb0 (variation of the surface band bending Esbb) leads to an increase of the e ciency of heterojunction with intrinsic thin layer solar cells.

Effects of bath composition on the morphology of electroless-plated Cu electrodes for hetero-junctions with intrinsic thin layer solar cell

The morphology of an electroless-plated Cu electrode was investigated as a function of bath composition. To enhance the selectivity of Cu electrode deposition on the surface of an indium tin oxide layer, a Ti/Cu multi-layer was deposited as a Cu electrode seed layer by physical vapor deposition, and then electroless plating was performed using various complexing agents and a surfactant. The degree of selectivity was effectively influenced by the type of complexing agent. The electroless plating solution containing N,N,N′,N′-tetrakis(2-hydroxypropyl)ethylenediamine (THPED) as complexing agent showed excellent selective growth of the Cu electrode as compared to the solution containing ethylenediaminetetraacetic acid. Even though THPED led to better selective growth of the electroless-plated Cu electrode, the aspect ratio of electrode lateral growth was about 2.7 times that of vertical growth. By adding a nonionic surfactant, the ratio between vertical growth rate and lateral growth rate was improved about 4.6 times. The Cu–THPED electroless plating with nonionic surfactant provided a drastic decrease in lateral growth rate, compared with the Cu–THPED electroless plating bath excluding nonionic surfactant. The Cu–THPED solution including nonionic surfactant is a promising composition of electroless plating solution for the clear selective plating of Cu electrodes on hetero-junctions with intrinsic thin layer solar cells.

Performance of hetero junction with intrinsic thin-layer solar cell depending upon contact resistivity of front electrode

Low temperature curing of Ag paste for electrode formation in silicon hetero junction (SHJ) solar cells is important for providing better device characteristics. Ag paste is composed of solvent, various organic materials, and additives; hence its electrical and mechanical adhesion properties depend on the curing conditions. The adhesion of the Ag paste was determined by scratch test, whereas the specific contact resistance was measured using the transfer length method. Various Ag electrodes were formed at various curing temperatures within the temperature range of 160°C–240°C, at 20°C intervals. The curing time was also varied for another set of Ag electrodes. With 200°C temperature and for 20-min curing, the critical load of 20.06 N and specific contact resistance of 19.61 mΩ·cm2 were observed. Using the same conditions, the efficiency of the SHJ solar cell was found to be improved by 3.8%.

Texturization and rounded process of silicon wafers for heterojunction with intrinsic thin-layer solar cells

Heterojunction with intrinsic thin-layer (HIT) solar cells are sensitive to interface state density. Traditional texture process for silicon solar cells is not suitable for HIT one. Thus, sodium hydroxide (NaOH), isopropanol (IPA) and mixed additive were tentatively introduced for the texturization of HIT solar cells in this study. Then, a mixture including nitric acid (HNO3), hydrofluoric acid (HF) and glacial acetic acid (CH3COOH) was employed to round pyramid structure. The morphology of textured surface and the influence of etching time on surface reflectance were studied, and the relationship between etching time and surface reflectance, vertex angle of pyramid structure was analyzed. It was found that the mixture consisting of 1.1 wt% NaOH, 3 vol% IPA and 0.3 vol% additives with etching time of 22.5 min is the best for HIT solar cells under the condition of 80°C. Uniform pyramid structure was observed and the base width of pyramid was about 2–4 μm. The average surface reflectance was 11.68%. Finally the effect of different processes on the performance of HIT solar cells was investigated. It was shown that these texturization and rounding techniques used in this study can increase short circuit current (Jsc), but they have little influence on fill factor (FF) and open circuit voltage (Voc) of HIT solar cells.

Sub-Bandgap External Quantum Efficiency in Ti Implanted Si Heterojunction with Intrinsic Thin Layer Cells

In this work we present the manufacturing processes and results obtained from the characterization of heterojunction with intrinsic thin layer solar cells that include a heavily Ti ion implanted Si absorbing layer. The cells exhibit external circuit photocurrent at photon energies well below the Si bandgap. We discuss the origin of this below-bandgap photocurrent and the modifications in the hydrogenated amorphous intrinsic Si layer thickness to increase the open-circuit voltage.

Determination of the Interface States in Amorphous/Crystalline Silicon Using Surface Photovoltage Spectroscopy

The interface state level at amorphous/crystalline silicon (a-Si:H/c-Si) heterojunctions is identified with surface photovoltage spectroscopy (SPS). A positive slope alteration of SPS in 1.2 eV indicates there is a primarily empty state at Ev(c-Si)+0.75 eV. Using hydrogen plasma treatment (HPT) on c-Si surface, we observed a systematic variation in the SPS signal upon HPT time, which was associated to the change of interface state density. Our results show that the SPS can be used to optimize the heterojunction with intrinsic thin-layer solar cell preparation process.

Processed optimization for excellent interface passivation quality of amorphous/crystalline silicon solar cells

This study evaluates the interface passivation quality of the amorphous/crystalline heterointerface and the performance of the heterojunction with intrinsic thin layer solar cells via values of a plasma parameter characterized by the deposition pressure (p)×electrode distance (d). Increasing the product of p×d leads to a lower crystalline fraction and higher hydrogen content, and enhances the c-Si surface passivation. This p×d evaluation factor is also compared with other evaluation factors, such as the silane depletion fraction and film-crystallinity. The tendencies of minority carrier lifetimes with respect to these evaluation factors were similar. Using the highest p×d value of 48, the photovoltaic parameter of the device yielded an open-circuit voltage of up to 710mV, in turned giving an efficiency of 19.12%.