Efficiency Of Silicon Solar Cells Research Articles

Photon management of combining nanostructural antireflection and perovskite down-shifting composite films for improving the efficiency of silicon solar cells

Photon management is an efficient route to ameliorate optical issues for improving the efficiency of solar cells. On account of reflection loss and spectral mismatch for silicon solar cells, we herein firstly demonstrate a photon management of combining antireflection and luminescence down-shifting coatings to simultaneously suppress the reflection of incident light with nanoporous structure and improve the spectra response of silicon solar cells in short wavelength with in-situ fabricated perovskite quantum dots composite film. Antireflection film can be obtained by sacrificing CdxZn1-xSeyS1-y/ZnS quantum dots template in PDMS composite film, which can bring 9.7% improvement in photocurrent for amorphous silicon solar cells. By further combining perovskite quantum dots down-shifting luminescence coating, an absolute improvement of 1.05% in power conversion efficiency was achieved. The photon management combining the antireflection and luminescence down-shifting coatings could provide a low-cost, simple but effective way to address the optical issues and improve the device performance of optoelectronic devices.

The effect of adding conductive polymers to the efficiency of silicon solar cells

Poly(3,4-ethylenedioxythiophenei) poly(styrenesulfonate) (BEDOT:PSS) and Poly Aniline (PANI) thin films was grown onto silicon solar cells by Dip-coating deposition method at thickness (100 nm). The optical properties were studied by using UV-V is absorption spectra. The surface morphology of the films was characterized by a scanning electron microscope SEM and the current–voltage characteristics of solar were measured, Values from 8.64, 7.21 by type of conductive polymers.

Optoelectronic properties of ultrathin ALD silicon nitride and its potential as a hole-selective nanolayer for high efficiency solar cells

Fully exploiting the power conversion efficiency limit of silicon solar cells requires the use of passivating contacts that minimize electrical losses at metal/silicon interfaces. An efficient hole-selective passivating contact remains one of the key challenges for this technology to be deployed industrially and to pave the way for adoption in tandem configurations. Here, we report the first account of silicon nitride (SiNx) nanolayers with electronic properties suitable for effective hole-selective contacts. We use x-ray photoemission methods to investigate ultra-thin SiNx grown via atomic layer deposition, and we find that the band alignment determined at the SiNx/Si interface favors hole transport. A band offset ratio, ΔEC/ΔEV, of 1.62 ± 0.24 is found at the SiNx/Si interface for the as-grown films. This equates to a 500-fold increase in tunneling selectivity for holes over electrons, for a film thickness of 3 nm. However, the thickness of such films increases by 2 Å–5 Å within 48 h in cleanroom conditions, which leads to a reduction in hole-selectivity. X-ray photoelectron spectroscopy depth profiling has shown this film growth to be linked to oxidation, and furthermore, it alters the ΔEC/ΔEV ratio to 1.22 ± 0.18. The SiNx/Si interface band alignment makes SiNx nanolayers a promising architecture to achieve widely sought hole-selective passivating contacts for high efficiency silicon solar cells.

Fabrication of low cost nano-grass n-type C-Si solar cell with sol–gel Al2O3 passivation

Silicon nano-grass Solar cell has the advantage of enhancing efficiency with cost effective method. Highly ordered silicon nano-grass is formed by chemical etching process. During this chemical etching unwanted nanograss is formed on both side of the wafer, resulting considerable transmission loss from rear side. This results in ultimate reduction of efficiency. The detrimental effect of nano-grass formation on both side of the wafer is briefly demonstrated here by simulation methods. Adopting the idea by simulation method this paper has reported silicon front sided nano-grass n-type c-Si solar cell by spin on diffusion source and rapid thermal annealing. The sheet resistance of the nano-grass silicon wafer is varied with respect to different spin-on diffusion profile. Later front surface has been passivated by sol–gel Al2O3 passivation. Eventually all the spin doped silicon nano-grass solar cell with sol–gel Al2O3 passivation provides a very promising route of cost effective high efficiency silicon solar cell technology. Broadband reflection between 300 and 1100 nm wavelengths has been suppressed to 2% for nano-grass Solar cell and maximum efficiency of 16.57% is achieved.

Efficiency enhancement of silicon solar cells by silicon quantum dots embedded in ZnO films as down-shifting coating

In the present work, the incorporation of silicon quantum dots (SiQDs) in zinc oxide (ZnO) films to develop coatings that improve the efficiency of silicon solar cells is reported. The down-shifting conversion of the SiQDs was used to enhance the efficiency of a photovoltaic device. The room temperature spectrum centered at 510 nm (2.43 eV) for the SiQDs is shown. The transmittance of the SiQDs-ZnO samples was measured and the band gap (Eg) was estimated through Tauc’s method. An increase on the band gap from 3.35 to 3.55 eV as function of the incorporation of SiQDs was obtained. The influence of the SiQDs in the oxide crystallinity of the wurtzite structure was studied through the X-ray diffraction. To determine the current increase under a standard test condition (STC) was achieved and an overall efficiency of 17.58% was obtained using a SiQDs-ZnO coating on silicon solar cells. The synergistic effect of SiQDs addition to ZnO films was demonstrated.

Luminescent anti-reflection coatings based on down-conversion emission of Tb3+-Yb3+ co-doped NaYF4 nanoparticles for silicon solar cells applications

To improve energy conversion efficiency (Eff) of silicon solar cells, luminescent down-conversion (DC) is an effective approach to adjust solar spectrum by converting ultraviolet light to visible and near-infrared light. In this paper, Tb3+- Yb3+ co-doped NaYF4 phosphors (DCNPs) were successfully synthesized by a simple solvothermal method. It was confirmed from the strong photoluminescence excitation (PLE) and photoluminescence (PL) emission peaks that the energy transfer occured between Tb3+ and Yb3+ ions. The DCNPs were added in the SiO2 sol-gel to prepare anti-reflection coatings with DC performance, enhancing the visible and near-infrared region transmittance which matched with the band gap of silicon. An optimized short-circuit current density (Jsc) of 33.39 mA/cm2 and a relatively enhanced Eff of 6.74% were achieved in the silicon solar cells with the bi-functional film. These results indicated the availability of anti-reflection coating with DCNPs for improving energy conversion efficiency of silicon solar cells.

Synthesis and characterization of MAPbI3 thin film and its application in C-Si/perovskite tandem solar cell

Silicon, polymer and dye sensitized have been increasing rapidly in thin film of solar cells. Recently, perovskite is proposed as alternative material in the fabrication of solar cells. In this study, methyl ammonium lead triiodide (MAPbI3, CH3NH3PbI3) perovskite thin film was prepared by two-step process of spin coating. The preparation process of thin film is summarized by reaction between the methyl ammonium iodide (CH3NH3I) and lead iodide (PbI2). The absorbent layer of the prepared perovskite solar cell is based on the MAPbI3 (CH3NH3PbI3) thin film. The conversion efficiency of p-n silicon solar cells can be improved by preparing tandem solar cells. The X-ray diffraction result of the MAPbI3 perovskite film manifested that it is polycrystalline with tetragonal system having a crystallite size of about 40 nm. The absorption spectrum of perovskite film was recorded by Ultra Violet–Visible spectrophotometer. The energy band gap of the MAPbI3 film calculated by Tauc’s formula was ~ 1.51 eV. The field emission scanning electron microscope image of the MAPbI3 film surface elucidated a cubic-like crystal structure and other irregular structures also. The atomic force microscope image and the distribution chart of the grains of the film displayed that the grain size was ~ 58.7 nm. The results demonstrated that the conversion efficiency for silicon, perovskite and tandem (silicon/perovskite) solar cells are 3%, 4.83% and 7.42%, respectively.

A Method to Quantify the Collective Impact of Grain Boundaries on the Internal Quantum Efficiency of Multicrystalline Silicon Solar Cells

Herein, a method to quantify the amount of reduction in the internal quantum efficiency (IQE) of multicrystalline silicon solar cells that can be attributed to grain boundaries is presented. By correlating the IQE maps obtained via light beam induced current (LBIC) topography with optical images of Secco‐etched samples, the distribution of IQE values at the positions of grain boundaries can be compared with the distribution of IQE values for all other positions where other defects may exist. The segmentation of IQE at 826 nm maps of the samples shows grain boundaries to be more detrimental compared with the combined effects of all other defects that may exist in other regions of the cell. The grain boundaries reduce the average IQE by up to 4.07% absolute for the cell from the bottom of the ingot.

Improving the Passivation of Molybdenum Oxide Hole‐Selective Contacts with 1 nm Hydrogenated Aluminum Oxide Films for Silicon Solar Cells

Silicon Solar Cells Precisely inserting hydrogen in few monolayer aluminum oxide passivation layer during atomic layer deposition (ALD) can lead to carrier lifetimes of over one millisecond. Coupling this layer with an ALD hole-selective molybdenum oxide film results in a low resistivity, fully transparent, passivating hole contact. This film stack can be integrated in highly efficient silicon solar cells. More details can be found in article number 2000093 by Kristopher O. Davis and co-workers.

Effect of Fresnel Reflection on Limit Photoconversion Efficiency in Silicon Solar Cells

The limit photoconversion efficiency of silicon solar cells is calculated assuming Lambertian light trapping of the incident solar radiation with AM1.5 G spectrum. Fresnel reflection of the trapped photons from the front surface has been neglected in the previous works. Here, a more accurate absorptance expression is used with Fresnel reflection properly included. As a result, a new photoconversion efficiency limit of 29.99% is found. It exceeds the latest reported value by as much as 0.27%-abs.

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.

Atomic Layer Deposition of Vanadium Oxide as Hole‐Selective Contact for Crystalline Silicon Solar Cells

AbstractHigh carrier recombination loss at the contact regions has become the dominant factor limiting the power conversion efficiency (PCE) of crystalline silicon (c‐Si) solar cells. Dopant‐free carrier‐selective contacts are being intensively developed to overcome this challenge. In this work, vanadium oxide (VOx) deposited by atomic layer deposition (ALD) is investigated and optimized as a potential hole‐selective contact for c‐Si solar cells. ALD VOx films are demonstrated to simultaneously offer a good surface passivation and an acceptable contact resistivity (ρc) on c‐Si, achieving a best contact recombination current density (J0) of ≈40 fA cm−2 and a minimum ρc of ≈95 mΩ.cm2. Combined with a high work function of 6.0 eV, ALD VOx films are proven to be an effective hole‐selective contact on c‐Si. By the implementation of hole‐selective VOx contact, the state‐of‐the‐art PCE of 21.6% on n‐type c‐Si solar cells with a high stability is demonstarted. These results demonstrate the high potential of ALD VOx as a stable hole‐transport layer for photovoltaic devices, with applications beyond c‐Si, such as perovskite and organic solar cells.

Illumination-Dependent Requirements for Heterojunctions and Carrier-Selective Contacts on Silicon

High efficiency silicon solar cells generally feature heterojunction or carrier-selective contact architectures, for which there is current interest in developing structures using a wide range of materials. The electrical and optical requirements that these layers must fulfill have been investigated previously for standard test conditions. Here, we investigate how the required work functions and layer thickness differ under other illumination conditions. The differences will be important for the optimization of tandem device subcells, and for devices which are intended for use in low-light conditions or under low-level concentration. Heterojunction cells are fabricated and the effect of reduced contact thickness and doping at different illumination levels is experimentally demonstrated. Simulations of a-Si/c-Si heterojunctions and ideal metal-semiconductor junctions reveal a logarithmic variation with illumination level of 0.1–10 suns in the electrode work function, and the heterojunction contact layer work function and thickness required to minimize efficiency losses.

Improvement of light-harvesting efficiency of amorphous silicon solar cell coated with silver nanoparticles anchored via (3-mercaptopropyl) trimethoxysilane

Owing to small size effect and large surface area, silver nanoparticles (Ag NPs) exhibit special physical properties and are widely used in different applications. One of the significant applications is that Ag NPs can be coated on the glass surface of solar cell to increase the light-harvesting efficiency of solar cell due to the plasmonic resonance and scattering effect. In this study, Ag NPs used for the coating of solar cells were synthesized via a chemical reduction method. The effect of the concentration of sodium borohydride (NaBH4) as reducing agent and 1-dodecanethiol (DDT) as capping agent on the size and shape of Ag NPs synthesized have been investigated. The synthesized Ag NPs were characterized using UV–vis spectroscopy, X-ray diffraction, energy-dispersive X-ray spectrometry and ATR-FTIR spectroscopy; while the particle size, morphology and topology of Ag NPs were examined by scanning electron microscopy and atomic force microscopy. By coating the glass surface of amorphous silicon solar cells with a uniform array of Ag NPs with the particle size of > 350 nm, a power conversion efficiency (PCE) enhancement of approximately 41% has been achieved. (3-mercaptopropyl) trimethoxysilane (MPTMS) was used as the adhesion promoter to anchor Ag NPs on the silicon surface of solar cells. With 7% of MPTMS, the array of Ag NPs formed on the glass surface was found being the most evenly distributed with a densely packed surface coverage, which resulted in 46% of PCE enhancement of the silicon solar cells.

Edge effect in silicon solar cells with dopant-free interdigitated back-contacts

Dopant-free heterojunction opens new doors to highly efficient silicon solar cells with interdigitated back-contacts (IBC) via an easy hard-mask processing. However, the existence of inevitable overlap between the hole- and electron-transport layers may cause edge leakage and recombination, which will deteriorate the power conversion efficiency. Here we unambiguously determined the edge recombination and recombination losses quantitatively, in combination with detailed comparisons in photovoltaic parameters, dark and light current-voltage ( I–V ) curves, partially illuminated I–V curves, of the hard-mask processed and the lithography processed IBC devices. Without the interfacial passivation layer, the solar cells fabricated by the hard-mask method suffer severe edge recombination with loss of 3 × 10 −4 A and a quite poor fill factor ( FF ) of ~66%, suggesting that the edge recombination could be another important issue affecting the FF besides the series resistance. With the clear understanding of the edge effect, we finely control the edge overlap, and finally obtained silicon dopant-free solar cells (with of intrinsic amorphous silicon as passivation layer) with over 20% efficiency and 73% FF either by lithography or by hard-mask methods. • Figuring out the edge recombination is one of the important items affecting the Fill Factor in IBC-DFHJ solar cells. • A series of new methods are provided to quantitatively and positionally analyze this edge recombination. • By well suppressing the edge recombination, IBC-DFHJ solar cells with a promising PCE of 20.6% was realized.

Effect of Etching Temperature on the Surface Texturing of Si{100} in an Extremely Low Concentration Tmah for Minimized Reflectivity

Among various renewable energy resources, solar energy is one of the most abundant energy available in nature. The solar energy can be utilized by converting photon energy into electrical energy by using solar cells as energy harvesters. Silicon-based solar cells dominate the current photovoltaic market because of its higher efficiency, excellent stability, non-toxicity, lower processing cost and excellent reliability in the outdoor conditions.1 However, the silicon solar cell efficiency can be further increased by reducing the front surface reflection from silicon, which is greater than 35%. In order to reduce the reflection from silicon surface, surface texturing is done where silicon surface is intentionally made rough. Wet anisotropic etching is most widely used in surface texturing of silicon because of its high throughput and lower cost. Potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) are two most extensively used alkaline solution for surface texturing of silicon. 2-4 In these two etchants, TMAH is preferred because it is fully compatible with CMOS process and also provide high etch selectivity between silicon and silicon dioxide. Surface texturing using low concentration TMAH (<5%) results in high surface roughness. This is a remarkable observation that can be applied in solar cell industries to minimize the reflection from silicon front surface.In this work, we have studied the effect of very low concentration TMAH (1.0-0.1 wt%) without adding any additive and agitation during etching for surface texturing of Si{100} surface. The main objective of this study is to achieve an optimized etched surface topography at lowest possible etching concentration and etching time to minimize the reflectance for application in solar cells. The average solar weighted reflectance (Rsw) of around 10% is obtained in a very mild etching conditions. Compared to the previous results reported in literatures and also the mild etching conditions, reflectance values obtained in this work are quite promising for large area surface texturing of silicon solar cell panels for enhancement in their efficiency. In addition, the use of very low concentration TMAH minimizes the chemical waste. This also helps in adopting the technique for fabricating anti-reflective silicon surfaces at large scale.

Simulation of multi-layer antireflection film for crystalline silicon solar cell

Based on the design theory of single-layer, double-layer and multi-layer antireflection films, the thickness and refractive index of each layer of three-layer antireflection films are designed and calculated. The theoretical results of double-layer and three-layer antireflection films was simulated by PC1D, and reflectance, internal and external quantum efficiency and device characteristics of solar cells with double-layer and three-layer antireflection coatings were comparative studied. The results show that the three-layer antireflection film has a wider wavelength response range and higher external quantum efficiency, and the conversion efficiency of the three-layer antireflection film Crystalline silicon solar cells is improved by 0.2% compared with the double-layer antireflection film Crystalline silicon solar cells.

Passivating contacts and tandem concepts: Approaches for the highest silicon-based solar cell efficiencies

The efficiency of photovoltaic energy conversion is a decisive factor for low-cost electricity from renewable energies. In recent years, the efficiency of crystalline silicon solar cells in mass production has increased annually by about 0.5–0.6%abs per year. In order to maintain this development speed, new technologies must be developed and transferred to industrial production. After the transition from full area Al back surface field cells to passivated emitter and rear contact cells, passivating contacts are an important step to get as close as possible to the efficiency limit of single junction Si solar cells. The theoretical background and the two prominent technologies for passivating contacts are presented and discussed. After implementing passivating contacts, the fundamental limit of single junction Si solar cells of 29.4% is in reach. Multi-junction solar cells are the most promising option to achieve efficiencies greater than 30%. Tandem technologies based on crystalline silicon as bottom cells have the advantage that they are based on a mature technology established on a gigawatt scale and can partially use the existing production capacity. In addition, silicon has an ideal bandgap for the lower subcell of a tandem solar cell. The two most promising material candidates for the top cell, i.e., III/V and perovskites, will be discussed. The presented technology routes show that silicon is able to maintain its outstanding position in photovoltaics in the coming years.

Reducing light reflection by processing the surface of silicon solar cells

This study discussed a surface processing technique for improving the energy conversion rate of solar cells with silicon as the substrate. The technique involves texturing the surface of a silicon substrate and coating it with an antireflective layer to enhance its antireflective property and thereby its photoelectric conversion efficiency. Double surface texturing (DST) texture was formed through photolithography and anisotropic wet etching, and radio frequency magnetron sputtering was performed to deposit the SiO2/TiO2 double-layer antireflective coating to reinforce the surface texture of a silicon solar cell. Subsequently, a scanning electron microscope was employed to analyze the DST texture before and after the surface was coated with a double-layer antireflective coating (ARC). An UV–VIS spectrophotometer attached with an integrating sphere was then applied to measure the light absorption rate of the processed surface at different wavelengths. After optimum DST and double-layer ARC treatments, the average reflectance within the visible light reduce to 9.94%, which means the absorption of incident light into the absorption layer was enhanced to improve the energy conversion efficiency of silicon solar cells.

Efficiency enhancement of silicon solar cells covered by GeO2-PbO glasses doped with Eu3+ and TiO2 nanoparticles

An objective of the solar industry is to improve the efficiency of the light -electricity conversion process of photovoltaic solar cells. An alternative to achieve this purpose is to manage the solar spectrum that is absorbed by the solar cell in order to match it with the solar cell responsivity. It can be done, for example through the downconversion process, covering the solar cell with photonic materials that can convert photons of the UV region to photons with energy close to the band gap energy of the solar cell. This process can be observed, for example, through the UV excitation of transparent glasses with low phonon energy hosting luminescent ions with energy levels in the VIS region. The luminescence from these energetic levels can be improved siting the luminescent ions in places with low symmetry. In the present study the optical response to the solar spectrum of GeO2-PbO glasses containing Eu3+ ions and titanium dioxide nanoparticles was explored to enhance the efficiency of polycrystalline silicon solar cells. Results revealed a maximum efficiency enhancement of 15.92% for the silicon solar cell covered with GeO2-PbO glass doped with 1% of Eu2O3 and 0.5% of TiO2 heat treated for 24 h. This efficiency enhancement was attributed to the location of the Eu3+ ions in sites of low symmetry of TiO2 nanoparticles.