Film Amorphous Silicon Solar Cells Research Articles

Dual metallic-based plasmonic back reflector to broaden the absorption spectra of a thin film amorphous silicon solar cell

Here, to obtain high efficiency in a thin film amorphous silicon solar cell, a dual metallic plasmonic back reflector was investigated. The designed dual metal plasmonic back reflector can improve the photocurrent and hence the efficiency. At first, a double layer SiO 2/Si3N4 as the antireflection (AR) was analyzed. The efficiencies of 8.74%, 11.38%, 12.53%, and 13.04% are obtained for a cell without AR, with SiO2, Si3N4, and SiO2/SiN 4 AR layers, respectively. A disk-ring and dual rings-based Ni and Ti-based plasmonic back reflector were designed. The study was carried out by a 3D finite difference time domain method and the optimized parameters were calculated to obtain higher efficiencies. Finally, a relatively higher photocurrent and conversion efficiency of 19.86mA/cm2 and 15.65% were achieved for the optimized structure with a dual Ni rings back reflector, respectively. Because of the importance of amorphous silicon solar cells due to the cost problem of crystalline silicon, here, the simulation steps present a valuable road map to design a novel plasmonic thin-film amorphous silicon solar cell.

Optimization of distributed Bragg’s reflectors in thin film solar cells

Distributed Bragg reflectors (DBRs) or one-dimensional photonic crystals (1DPCs) play key role in advanced opto-electronic and photonic devices. The term photonics is derived from photons in which particle indicates a quantum of light and photon carries energy proportional to the radiation frequency with zero rest mass. In this work, we present the designing 1DPCs by using Si/SiO2 layers using a plane wave expansion method (PWE). For that, various parameters are optimized such as thicknesses (d) of each layer, center wavelength (λc), refractive index (nH/nL) of individual layer and the number of DBR/period to analyze the photonic band gap (PBG). The transverse electric (TE) and magnetic (TM) field distribution at different wavelength is discussed and helpful to understand the light harvesting mechanism within the PBG. Finally, this optimized DBR layers were integrated into a thin film amorphous silicon solar cell as a back-end reflector. Due to the tuned PBG, the proposed and designed amorphous silicon thin film solar cell has yielded an improved of light absorption, which is useful for enhancing the photovoltaic performance.

Ultrathin Film Amorphous Silicon Solar Cell Performance using Rigorous Coupled Wave Analysis Method

The issues related to global energy needs and environmental safeties as well as health crisis are some of the major challenges faced by the human, which make us to generate new pollution-free and sustainable energy sources. For that the optical functional nanostructures can be manipulated the confined light at the nanoscale level. These characteristics are emerging and leading candidate for the solar energy conversion. The combination of photonic (dielectric) and plasmonic (metallic) nanostructures are responsible for the development of better optical performance in solar cells. Here, the enhancement of light trapping within the thin active region is the primary goal. In this work, we have studied the influence of front-ITO (rectangular) and back-Ag (triangular) nanogratings were incorporated with ultrathin film amorphous silicon (a-Si) solar cell by using rigorous coupled wave analysis (RCWA) method. The improvement of light absorption, scattering (large angle), diffraction and field distributions (TE/TM) were demonstrated by the addition of single and dual nanogratings structures. Significantly, the plasmonic (noble metal) nanogratings are located at the bottom of the cell structure as a backside reflector which is helpful for the omni-directional reflection and increased the path length (life time) of the photons due to that the collection of the charge carriers were enhanced. Further, the proposed solar cell structure has optimized and compared to a back-Ag, front-ITO and dual nanogratings based ultrathin film amorphous silicon solar cell. Finally, the obtained results were evidenced for the assistance of photonic and plasmonic modes and achieved the highest current density (Jsc) of 23.82 mA/cm2(TE) and 22.75 mA/cm2 (TM) with in 50 nm thin active layers by integration of (dual) cell structures.

The role of photonic and plasmonic modes in ultrathin amorphous silicon solar cells using finite difference time domain method

In photovoltaic market, the enhancement of optical performance in an ultra-thin film amorphous silicon (a-Si) solar cell is significant. Our main objective is to design and simulate a highest current density by using various nanostructures integrated with ultrathin a-Si solar cells. In this proposed work, the various photonic and plasmonic nanostructures were used in front side of the absorber layer and enhanced the collection of charge carriers due to that an improved the current density in ultrathin a-Si solar cells. Using finite-difference time-domain (FDTD) method, the obtained results indicate the optimized SiO2 nanogratings and Si3N4 thin films acting as an anti-reflection coating (ARC) layer with air medium (AM1.5) which showed significant current density of 16.25 mA/cm2 in ultra-thin a-Si solar cells. Finally, the light trapping mechanism evidenced the importance of nanostructures using transverse electric (TE) and magnetic (TM) field distributions by changing the various incident wavelength.

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

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

Study of ultrathin‐film amorphous silicon solar cell performance using photonic and plasmonic nanostructure

The photonic and plasmonic nanostructures are highly feasible for enhanced light trapping mechanisms. These nanostructures hold great promises for better photovoltaic performance by yielding the highest light-harvesting photons within the few nanometer absorber regions. The shed light on the nano-scaled structures (thin films and nanogratings) is responsible for the highest scattering mechanism with the omnidirectional diffraction angles and enhanced life time of the photons. In this research work, we have focused on improved ultrathin film amorphous silicon (a-Si) solar cell performance, which was integrated by top-SiO2 and bottom-Ag nanogratings as a backside reflector by using rigorous coupled-wave analysis method. The SiO2 antireflection coating, nanogratings, and absorber (a-Si) layer thicknesses were optimized for better photovoltaic performance. With the influence of optimization parameters, the highest current density of 27.03 and 33.53 mA/cm2 were obtained from transverse electric and transverse magnetic polarization conditions due to the surface guided-mode, Fabry–Perot resonance, surface excitation, localized fields, and surface plasmon polariton modes.

Solar photovoltaic technology: A review of different types of solar cells and its future trends

The Sun is source of abundant energy. We are getting large amount of energy from the Sun out of which only a small portion is utilized. Sunlight reaching to Earth’s surface has potential to fulfill all our ever increasing energy demands. Solar Photovoltaic technology deals with conversion of incident sunlight energy into electrical energy. Solar cells fabricated from Silicon aie the first generation solar cells. It was studied that more improvement is needed for large absorption of incident sunlight and increase in efficiency of solar cells. Thin film technology and amorphous Silicon solar cells were further developed to meet these conditions. In this review, we have studied a progressive advancement in Solar cell technology from first generation solar cells to Dye sensitized solar cells, Quantum dot solar cells and some recent technologies. This article also discuss about future trends of these different generation solar cell technologies and their scope to establish Solar cell technology.

Integration of RF rectenna with thin film solar cell to power wearable electronics

AbstractThis paper reports an integration of dual band microstrip antenna with thin film amorphous silicon solar cell which creates a wearable system to harvest microwave energy. The multiple layers in the encapsulation of the thin film solar cell are used as a substrate for microstrip antenna. The rectifier and matching circuit are designed on cotton jeans material and the whole system is mechanically supported by the foam of 5 mm thick. The performance of the antenna is studied for the mechanical bending condition. The device has maintained good power conversion efficiency. The efficiency of the voltage doubler is tested by varying radio frequency power levels from −30 to10 dBm. The voltage doubler conversion efficiency at 1.85 and 2.45 GHz are 58 and 43%, respectively, for a load of 7.5 kΩ for an input power level of −5 dBm.

On KCN treatment effects on optical properties of Si-based bilayers

Abstract In this paper we report results from optical transmittance spectroscopy complemented with data from Raman scattering measurements to determine optical properties of two series of silicon based bilayers deposited by PECVD on glass substrate (intrinsic a-Si:H/p-type a-SiC:H and n-type mc-Si:H/intrinsic a-Si:H). These samples represent segments of common p-i-n thin film amorphous silicon solar cells with intrinsic hydrogenated silicon (a-Si:H) as the solar absorber. The members of the series differ by the KCN treatment conditions. Dispersive and absorptive optical properties – refractive indices, absorption coefficients and optical band gaps were determined from transmittance spectra. Each bilayer was considered as one effective thin film the optical properties of which can be regarded as effective optical properties of the bilayer structure. After KCN treatments refractive indices were modified probably due to the structural changes of bilayers. Moreover the effect of the solvent used in KCN solutions was recognized. Optical band gaps calculated either by the Tauc procedure or determined as iso-absorption levels were found to be only slightly KCN treatment dependent.

Broadband light trapping in nanotextured thin film photovoltaic devices

Substrates with engineered roughness are studied with the aim of achieving broadband and omnidirectional photon harvesting in thin film devices. Light coupling across the interfaces of a photonic device is induced by uniaxial pseudo-periodic gratings formed in a self-organised fashion via de-focused ion beam sputtering (IBS). The optical properties of the textured interfaces are assessed both experimentally and numerically using finite difference time domain (FDTD) algorithm, quantitatively demonstrating the optimal geometries which favour broadband diffuse scattering of radiation across the Vis-NIR spectral range. Thin film amorphous silicon solar cells based on the nanostructured patterns have been numerically studied via FDTD to assess absorption enhancement in comparison to flat reference devices, finding a 25% increase of short-circuit current, in good agreement with the experiment. Similar light trapping experiments performed on prototypical solar cells employing a PTB7:PC61BM organic absorber, allow to extend the general validity of the results to a relevant class of materials in the view of photovoltaic applications.

Improving the Efficiency of Thin Film Amorphous Silicon Solar Cell by Changing the Location and Material of Plasmonic Metallic Nanostructures

In this work we present a 3D-finite difference time domain (FDTD) simulation of ultra thin amorphous silicon solar cell. The optical generation rate and plasmonic resonance enhance absorption in thin film cell in which silver nanoparticles are imbedded inside the depletion region of p-n junction. Here, the operation of thin film solar cell has been analyzed. Here, by inserting the metal nanoparticles within the active layer in the depletion region of the p-n junction, a new structure has been introduced. We have utilized three different materials, gold, silver and aluminium and the efficiencies of 5.27%, 5.3% and 3.74% have been obtained respectively. The results indicate a significant increase in the efficiency of proposed solar cell with silver nanoparticles.

The devisable reflection-enhanced lumpy silver particle and its application in thin film amorphous silicon solar cell

A tailored large-size plasmonic core-protuberances silver particle with unique optical properties with promising applications in thin-film solar cells was numerically and experimentally studied. The designed particle possesses an extremely enhanced electromagnetic near-field excited by localized surface plasmons resonance and its far field angular plots of light scattering power indicated an enhanced back-scattering ability. When embedded the lumpy particles into the rear of thin-film amorphous silicon solar cells, light trapping in broad wavelength range and ideal short circuit density of the cells increased. A simple one-step reaction was established to acquire the structured particles. The strengthening backward scattering capacity in a broadband light region was also verified experimentally.

Fabrication of honeycomb textured glass substrate and nanotexturing of zinc oxide front electrode for its application in high efficiency thin film amorphous silicon solar cell

A significant part of broad band sunlight remains unabsorbed in a simple structured amorphous silicon solar cell. This absorption can be enhanced by adopting a light-trapping scheme with the help of a textured front surface and back reflector. For this purpose, honeycomb-type texture was fabricated on a glass surface by chemical etching. A 3 μm×3 μm honeycomb patterned optical-mask was used to create an image-pattern of an etch-mask on the glass surfaces. We used 0.5% hydrofluoric acid (HF) as an etchant solution with an optimized etching time ranging between 25 and 28 min. This single textured glass shows an enhancement in diffused transmission of light. In solar cell application, a 630-nm-thick Al-doped ZnO (AZO) layer was deposited over the textured glass surface. An additional random etching was carried out on the AZO with 1% HF acid solution for 10 s. This results to a double textured AZO superstrate on which solar cells were fabricated. The solar cells show higher short circuit current density to 17.2 mA/cm2. Finally, we obtained photovoltaic conversion efficiency of an optimized solar cell as 10.75% (with the corresponding Jsc as 17.03 mA/cm2).

High efficiency thin‐film amorphous silicon solar cells

AbstractEnhancing light absorption within thin film amorphous silicon (a‐Si) solar cells should lead to higher efficiency. This improvement is typically done using various light trapping techniques such as utilizing textured back reflectors for pronounced light scattering within the cell thus achieving higher absorption. It is believed that embedding metallic nanoparticles (MNPs) inside the structure could increase light scattering. However, embedding MNPs can also cause significant structure defects and pronounced efficiency drop as well – it has been indicated by many experiments that disproved this belief. In search of ways to improve efficiency, we have investigated the impact of MNP's size, and location within the solar cell, in addition to the effect of defects, and doping levels on the overall efficiency. On the basis of our 3D multiphysics (optical‐electric) modeling, we developed a design guideline for embedding these MNPs and reducing the impact of defects created in the embedding process. The results of simulations were compared to relevant measured data, and it showed a good agreement. Subsequently, models were used to predict performance, and over 30% improvement in solar cell efficiency (~13% is predicted); which is beyond the state of the art. This was predicted by optimizing the size and location of the MNPs and tailoring the doping levels to have better forward light trapping and absorption.

Window p-layer in amorphous pin solar cells using ZnO as Transparent Conductive Oxide

The main steps of p-layer development in pin thin film amorphous silicon solar cell at TEL Solar are presented. First, the implementation of a new PECVD reactor is shown to contribute to an improvement in amorphous silicon carbide (a-SiC) p-layer quality probably by reducing the porosity and leading to an increased open circuit voltage after the solar cell is subjected to light soaking. Second, an alternative high flow deposition regime for the p-doped a-SiC layer was successfully developed improving the layer purity and electrical conductivity. And third, a softer deposition regime for the very first part of the p-layer, the contact layer, which plays a crucial role in the release of Zn from the TCO, contributes to a decreased overall Zn contamination.

Inverted nanocone-based thin film photovoltaics with omnidirectionally enhanced performance.

Thin film photovoltaic (PV) technologies are highly attractive for low-cost solar energy conversion and possess a wide range of potential applications from building-integrated PV generation to portable power sources. Inverted nanocones (i-cones) have been demonstrated as a promising structure for practical thin film PV devices/modules, owning to their antireflection effect, self-cleaning function, superior mechanical robustness, and so forth. In this work, we have demonstrated a low-cost and scalable approach to achieve perfectly ordered i-cone arrays. Thereafter, thin film amorphous silicon (a-Si:H) solar cells have been fabricated based on various i-cone substrates with different aspect ratios and pitches to investigate the impact of geometry of i-cone nanostructures on the performance of the as-obtained PV devices. Intriguingly, the optical property investigations and device performance characterizations demonstrated that the 0.5-aspect-ratio i-cone-based device performed the best on both light absorption capability and energy conversion efficiency, which is 34% higher than that of the flat counterpart. Moreover, the i-cone-based device enhanced the light absorption and device performance over the flat reference device omnidirectionally. These results demonstrate a viable and convenient route toward scalable fabrication of nanostructures for high-performance thin film PV devices based on a broad range of materials.

Hetero-structured lumpy nanoparticle conformal structure for high absorbance of ultrathin film amorphous silicon solar cells

We present a concept for enhancing the absorbance of amorphous-silicon solar cells by using hetero-structured nanoparticles consisting of dielectric core particles combined with small metallic surface nanoparticles half embedded in the core to harness both the scattering effect and the near field light concentration. Through optimising key parameters, including the relative distance of the nanoparticles to the solar cell, the radius ratio of the core to the surface nanoparticles, and the refractive index of the core particles, the short circuit current density in a 20 nm nanoparticle-integrated active layer is equivalent to that in a 300 nm flat active layer.

Development of n-μc-SiOx:H as cost effective back reflector and its application to thin film amorphous silicon solar cells

Development of doped silicon oxide based microcrystalline material as a potential candidate for cost-effective and reliable back reflector layer (BRL) for single junction solar cells is discussed in this article. Phosphorus doped μc-SiOx:H layers with a refractive index ∼2 and with suitable electrical properties were fabricated by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) technique, using the conventional capacitively coupled reactors. Optoelectronic properties of these layers were controlled by varying the oxygen content within the film. The performance of these layers as BRL have been investigated by incorporating them in a single junction amorphous silicon solar cell and compared with the conventional ZnO:Al based reflector layer. Single junction thin film a-Si solar cells with efficiency ∼9.12% have been successfully demonstrated by using doped SiO:H based material as a back reflector. It is found that the oxide based back reflector shows analogous performance to that of conventional ZnO:Al BRL layer. The main advantage with this technology is that, it can avoid the ex-situ deposition of ZnO:Al, by using doped μc-SiO:H based material grown in the same reactor and with the same process gases as used for thin-film silicon solar cells.

Design and Analysis of Spectrally Selective Patterned Thin-Film Cells

This paper outlines several techniques for systematic and efficient optimization as well as sensitivity assessment to fabrication tolerances of surface texturing patterns in thin film amorphous silicon (a-Si) solar cells. The aim is to achieve maximum absorption enhancement. The joint optimization of several geometrical parameters of a three-dimensional lattice of periodic square silver nanoparticles, and an absorbing thin layer of a-Si, using constrained optimization tools and numerical FDTD simulations is reported. Global and local optimization methods, such as the Broyden–Fletcher–Goldfarb–Shanno quasi-Newton method and simulated annealing, are employed concurrently for solving the inverse near-field radiation problem. The design of the silver-patterned solar panel is optimized to yield maximum average enhancement in photon absorption over the solar spectrum. The optimization techniques are expedited and improved using a novel nonuniform adaptive spectral sampling technique. Furthermore, the sensitivity of the optimally designed parameters of the solar structure is analyzed by postulating a probabilistic model for the errors introduced in the fabrication process. Monte Carlo simulations and unscented transform techniques are used for this purpose.

Self-organized broadband light trapping in thin film amorphous silicon solar cells

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p–i–n type thin film a-Si:H solar cells.