Conference PaperPDF Available

Anti-Reflection coatings for highly efficient solar cells

Authors:
Vikas .. at University of Glasgow
Vikas ..
Download full-text PDF
Read full-text
Download citation

Abstract

Efficiency of solar cell is a big issue in the present time. Anti-Reflection Coating plays very important role in improving the efficiency of solar cell. Anti-Reflection coating is typically specified by either the maximum allowable reflectance at a single wavelength or by the average allowable reflectance over a specified wavelength range. Anti-Reflection coatings intended for a single wavelength or a single angle of incidence and very high performance can be obtained less than 0.1% reflectance per surface at visible wavelengths on glass substrates. A single layer of thin film of thickness around 100nm of Silicon Dioxide (SiO2) and Titanium Dioxide (TiO2), increases solar cell efficiencies by 3-4% and a triple-layer coating can improve its efficiency by 39-40%. The reflectance of solar cell can be reducing up to 3.2% by using Anti-reflection coating. So, multilayer coatings of SiO2 and TiO2 can be used for highly conversion of solar spectrum into electrical energy.
Content uploaded by Vikas ..
Author content
All content in this area was uploaded by Vikas .. on Nov 22, 2016
Content may be subject to copyright.
Anti-Reflection coatings for highly efficient solar cells
Vikas*, Surya Narain Diksit
Department of Applied Physics
Guru Jambheshwar University of Science & Technology,
Hisar 125001, Haryana, India
* vikas5293@gmail.com
ABSTRACT
Efficiency of solar cell is a big issue in the present time. Anti-Reflection Coating plays very important role in improving the efficiency of solar cell. Anti-Reflection coating is typically specified by either
the maximum allowable reflectance at a single wavelength or by the average allowable reflectance over a specified wavelength range. Anti-Reflection coatings intended for a single wavelength or a
single angle of incidence and very high performance can be obtained less than 0.1% reflectance per surface at visible wavelengths on glass substrates. A single layer of thin film of thickness around
100nm of Silicon Dioxide (SiO2) and Titanium Dioxide (TiO2), increases solar cell efficiencies by 3-4% and a triple-layer coating can improve its efficiency by 39-40%. The reflectance of solar cell can
be reducing up to 3.2% by using Anti-reflection coating. So, multilayer coatings of SiO2 and TiO2 can be used for highly conversion of solar spectrum into electrical energy.
Introduction
•One of the main barriers of solar cell efficiency is reflection of light from
front of its surface. Because a bare silicon surface reflects the light about
30% and GaAs reflect the light about 32.58% light from their front
surface.
• The Intensity of light transmitted and reflected between two medium is
depend upon change in refractive index of mediums and angle of incident
of light at interference . The intensity of reflected light is given by fresenl
equation of reflection is
IR =

•Fresnel reflection at the front surface of the solar cell can be reduce by
using another optical phenomenon known as “Interference of light in thin
film”.
Fig :- fresnel reflection
IR
Design of Anti-Reflection Coating
•Antireflection coatings (ARCs) are applied to PV cells to ensure a gradual increase of the
refractive index as incident photons traverse from air through to the absorber so as to reduce the
backward reflection losses.
•We deposit a slab of material of thickness d and refractive index nf and expect that R3 and R5
interferes destructively and transfer energy inside slab.
d = /4nf IR = [ 
 nf =   
Fig:- basic principle of ARC Fig:- Physical arrangement of Photovoltaic solar cells with ARC
Discussion of Deposition Technique
•The SiO2 has good passivation and scratch resistant properties and chemically stable at elevated temperatures . Another material is TiO2 which has suitable refractive index and a
low absorption throughout the visible region. In addition TiO2 is known for its chemical stability mechanical hardness, less moisture absorption, and comparatively smooth
fabrication process .
•Sol-gel spin-coating method applied extensively in preparing lots of different kinds of coated films has become a popular technique for the past thirty years due to its high process
speed, low-cost, continuous production, and suitability for the large-area process.
• The sol-gel process is a method for producing solid materials from small molecules. This method is used for the fabrication of metal oxides, especially the oxides of Silicon and
Titanium.
•It provide uniformly distribution of anti reflection material on substrate than plasma enhanced chemical vapor deposition. Due to centrifugal force appears on four corners of
substrate non-uniformity appear. It can control by adjusted spin rate of spin coater and concentration of sol-gel.
•Sol-Gel method provide high efficient ARCs on large area multicrystalline wafers.
•The SiO2-TiO2 colloid solutions contained varying volume ratios of SiO2 and TiO2 solutions.
• The SiO2 solution can be prepared by reacting metal alkoxide with a mixture of a critical amount of water and hydrochloric acid (HCl) catalyst in a medium diluted with ethyl
alcohol solvent. Tetraethyl orthosilicate (Si(OC2H5)4) was then added into the resultant solutions and stirred with a magnetic stirrer.
•Similarly TiO2 solution can be prepared except that titanium isopropoxide (Ti(OC3H9)4) was added instead of (Si(OC2H5)4).The SiO2 and TiO2 were then mixed separately in
different volume ratios. Finally, a small amount of DMF was added into the SiO2-TiO2 synthetic colloid solution.
•Various parameter of solar cells with coating and without coating is given in table where Jsc gives short circuit current density, Voc gives open circuit voltage and efficency of solar
cell.
AR Coating Jsc (mA/cm2) Voc(V) η (%)
No ARC 21.60 .5717 8.92
TiO2 25.80 0.5766 10.78
ZnO 28.31 0.5792 11.77
ZnO/TiO2 31.91 0.5824 13.37
SiO2/TiO2 32.51 0.5829 13.59
Table:- Parameters of Solar cells with different Coating Fig:- Refractive index spectrum for pure TiO2 and SiO2-TiO2 composite films deposited
Results and Discussion
•Application of thin films of SiO2 and TiO2 using the sol-gel process were utilized
as antireflection coating on monocrystalline silicon wafers.
•For deposition of Anti-Reflection Coating on substrate Sol-Gel technique provide
uniform distribution of material. Refractive index of composition decreases from
2.1 to 1.45 as ratio of SiO2 to TiO2 (SiO2/TiO2) decreases as shown in figure at a
wavelength of 630 nm.
•It is expected that sol-gel-ARC device should absorb more incident light resulting in
higher current density. It improve the quality of sol-gel ARCs that could help
increase the efficiency of solar cells.
•It could enables a more efficient and a continuous mass production of Si solar cells
compared to the use of PECVD method, which requires an expensive vacuum
process and dangerous process gases. SiO2-TiO2 (sol-gel)
Fig:- Sol-Gel anti-reflection coated device
References
[1] M. Moradi, Z. Rajabi Efficiency Enhancement of Si Solar Cells by Using Nanostructured Single and Double Layer Anti-Reflective Coatings JNS 3 (2013) 365-369.
[2] Khuram Ali*, Sohail A. Khan, M. Z. Mat Jafri Effect of Double Layer (SiO2/TiO2) Anti-reflective Coating on Silicon Solar Cells Int. J. Electrochem Sci., 9 (2014) 7865 - 7874 .
[3] Chih-Hsiang Yang, Shui-Yang Lien, Chia-Ho Chu, Chung-Yuan Kung, Tieh-Fei Cheng, Pai-Tsun Chen Effectively Improved SiO2-TiO2 Composite Film Applied in Commercial
Multicrystalline Silicon Solar Cells International Journal of Photoenergy Volume (2013).
[4] S.-M. Jung, Y.-H. Kim, S.-I. Kim, and S.-I. Yoo, Design and fabrication of multi-layer antireflection coating for III-V solar cell, Current Applied Physics, vol. 11, no. 3, pp.,538–541, 2011.
[5] Yi-Yu Lee, Wen-Jeng Ho, Jhih-Kai Syu, Quan-Ru Lai, and Cheng-Ming Yu 17.9% Efficiency Silicon Solar Cells by Using Spin-on Films Processes PIERS Proceedings, Suzhou, China, September
12-16, (2011)
... An account of application of ARCs on solar cells and modules, contemporary research and associated challenges are presented in the end to facilitate a universal understanding of the ARCs and encourage future research.❖ In[16], Vikas presents research about "Anti-Reflection coatings for highly efficient solar cells".Anti-Reflection Coating plays very important role in improving the efficiency of solar cell. Anti-Reflection coating is typically specified by either the maximum allowable reflectance at a single wavelength or by the average allowable reflectance over a specified wavelength range. ...
Design of PV modules including a layer between solar cells and glass cover to increase PV module lifetime
Thesis
Full-text available
  • Jun 2019
The current design of photovoltaic (PV) modules integrates solar cells directly onto a protective tempered glass layer. Consequently, any damage to the cover glass necessitates the complete replacement of the entire PV module, leading to a loss of perfectly functional solar cells that remain undamaged. To address this issue, this study proposes an innovative solution involving the incorporation of a lamination layer between the solar cells and the tempered glass in PV modules.The proposed lamination layer allows for the replacement of the tempered glass alone in the event of damage, without the need to replace the entire PV module. This approach significantly reduces replacement costs, especially as PV systems reach the end of their operational lifespan. The study evaluates the feasibility and practicality of this design, highlighting its potential to dramatically lower the overall cost of PV systems by mitigating unnecessary wastage and extending the functional life of undamaged solar cells.
View
... The major hindrances to achieving high efficiencies in these solar cells are losses due to unwanted reflection (Zhiyong & Qingfeng, 2014), resistivity (Masahiko, Yoshihiro, Kousuke, & Jun-ichi, 2018), electron-hole recombination (Saïdou, Madougou, Mohamadou, & Sissoko, 2010) as well as thermal losses (Hirst & Ekins-Daukes, 2011). Among these losses, optical losses account to about 30% (Vikas & Surya, 2015). It has been reported that applying antireflection coatings to the solar cells can lead to increase in transmittance of incident photons (Gandham, Hill, Macleod, & Bowden, 1979). ...
Optical Modelling of TCO Based FTO/TiO2 Multilayer Thin films and Simulation in Hydrogenated Amorphous Silicon Solar Cell.
Article
  • Apr 2023
Hydrogenated Amorphous silicon (a:Si:H) has low amounts of defects making it attractive for photovoltaic applications. To improve power conversion efficiency (PCE) of a:Si:H solar cells, this study investigated the effect of introducing FTO/TiO2 multilayer thin films into its structure to serve as antireflection coating. The multilayer thin films were characterized and optimized by optical simulations using a computer program, GLSIM (glazing simulator). The program was written in FORTRAN and implemented in MATLAB. The multi-Fresnel equations were employed to create the GLSIM program. Then using the program, together with the pairs of real and imaginary values of complex refractive index, n and k respectively, the transmittance and reflectance data of FTO/TiO2 multilayer thin films on glass substrate were computed. The optimized FTO/TiO2 multilayer thin films were then incorporated into silicon solar cell with structure glass/FTO/TiO2/n-a-Si:H/i-a-Si:H/p-a:Si:H/P+-BSF and characterized using SCAPS-1D software. The effect of varying layer thickness on the solar cell performance was also investigated. The optimized solar cell had a thickness of 100 nm, 50 nm, 900 nm, 100 nm, 10μm and 5μm for FTO, TiO2, n-a-Si:H, i-a-Si:H, p-a-Si:H and P+-BSF respectively. The device output performance were 37.96 mA/cm2, 1.34 V, 56.37% and 28.72% for Jsc, Voc, FF and η respectively showing a remarkable improvement in the solar cell performance. These results show potential of fabricating an improved hydrogenated silicon solar cell.
View
... In this aspect electrical and optical properties of Solar cell have been introduced by some cost effective technique. There are different types of antireflection coating in the commercial production scale to reduce the reflectance [2,3]. Although the coating shows good optical property but the budget is high due to sophisticated fabrication unit. ...
Fabrication of low cost nano-grass n-type C-Si solar cell with sol–gel Al2O3 passivation
Article
Full-text available
  • Nov 2020
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.
View
Advancements and challenges in pulsed laser-deposited hydrophobic CeO2 film for broadband antireflection applications
Article
  • Oct 2023
Due to the remarkable progress in photovoltaic technology, enhancing efficiency and minimized the costs have emerged as global challenges for the solar industry. A crucial aspect of this advancement involves the creation of solar cell antireflection coating, which play a significant role in minimizing sunlight reflection on the cell surface. In this study, we report on the optimization of the characteristics of CeO2 films prepared by pulsed laser deposition through the variation of laser energy density. The deposited CeO2 nanostructure films have been used as an effective antireflection coating (ARC) and light-trapping morphology to improve the efficiency of silicon crystalline solar cell. The film’s thickness increases as laser fluence increase. The refractive index of the antireflective film is measured as a function of laser fluence. The properties of CeO2 thin films’ were characterized by various techniques. X-ray diffraction measurements show the grown films were crystalline with cubic and hexagonal phases. The degree of crystallinity of the film increases with the increase in the laser fluence. Scanning electron microscope results reveal that the film’s morphology and film uniformity improved as the laser fluence increases. Raman shift of the CeO2 film as a function of laser energy density was investigated. Photovoltaic properties show that the conversion efficiency of the silicon solar cell increases from 8.37 to 14.04% after deposited with ARC CeO2 film at laser energy density of 76.39 J/cm2. The CeO2 films deposited at 76.39 J/cm2 laser pulse energy density have highest hydrophobicity among all the prepared samples.
View
Sol-gel/ALD low temperature process : study of Al2O3 and codoped TiO2 nanostructures for photovoltaic applications
Thesis
  • Jul 2021
Solar energy remains one of the most common renewable energy sources. Using photovoltaic cells, the energy of sunlight can be converted into electricity. Unfortunately, one of the main drawbacks of Si solar cells is their limited efficiency absorption of long wavelength sunlight. To address this issue, special attention is given to the upconversion luminescence process in which the sequential absorption of two or more photons leads to the emission of light at shorter wavelength (Visible) than the excitation wavelength (Near Infra Red) that can be reabsorbed by the cell. In this context, the work of this PhD thesis aims to develop coated upconversion nanopowder based thin films to extend the spectral sensitivity of solar cells to the NIR (Near Infra Red) spectrum.The idea is to investigate the efficiency of a low temperature procedure to get an efficient upconversion emission that can be used to improve the performance of Si solar cells. The structural, morphological and composition properties after every step of the proposed approach are examined in details. For the nanopowder based thin film, TiO2 is chosen as host material and Er3+/Yb3+, embedded as activator/sensitizer, to play the role of spectrum modifier. This nanopowder based thin film is formed through an optimization of the dispersion (pH, ultrasonication) and deposition (spin coating parameters) steps of the elaborated upconversion nanopowder. The Atomic Layer Deposition (ALD) layer of Al2O3 material followed by thermal treatment is used as an important tool for Si passivation through defects reducing. In addition, its potential application as a barrier from the surrounding environment helps to avoid the supressing of luminescence. The influence of thickness layer and thermal treatment on upconversion luminescence and structural properties of the nanopowder-based films are studied. It is concluded that ALD reinforced nanopowder thin films retained the original functionality of the nanopowder related to upconversion phenomenon. Interestingly, by tuning the thickness of the coating layer, enhancement by 98% of the green upconversion emission can be obtained, it is proved that Al2O3 acts as a barrier to decrease the quenching of luminescence and promote the light absorption. Furthermore, the effect of ALD coating and thermal treatment on adhesion and hardness of the coated nanopowder based films is investigated. The combination of the common steps used for enhancing electrical properties with good luminescence and mechanical properties makes these films more attractive.
View
Effectively Improved SiO2-TiO2 Composite Films Applied in Commercial Multicrystalline Silicon Solar Cells
Article
Full-text available
Composite silicon dioxide-titanium dioxide (SiO2-TiO2) films are deposited on a large area of 15.6 × 15.6 cm2 textured multicrystalline silicon solar cells to increase the incident light trapped within the device. For further improvement of the antireflective coatings (ARCs) quality, dimethylformamide (DMF) solution is added to the original SiO2-TiO2 solutions. DMF solution solves the cracking problem, thus effectively decreasing reflectance as well as surface recombination. The ARCs prepared by sol-gel process and plasma-enhanced chemical vapor deposition (PECVD) on multicrystalline silicon substrate are compared. The average efficiency of the devices with improved sol-gel ARCs is 16.3%, only 0.5% lower than that of devices with PECVD ARCs (16.8%). However, from equipment depreciation point of view (the expiration date of equipment is generally considered as 5 years), the running cost (USD/watt) of sol-gel technique is 80% lower than that of PECVD method for the first five years and 66% lower than that of PECVD method from the start of the sixth year. This result proves that sol-gel-deposited ARCs process has potential applications in manufacturing low-cost, large-area solar cells.
View
Effect of Double Layer (SiO2/TiO2) Anti-reflective Coating on Silicon Solar Cells
Article
  • Dec 2014
  • INT J ELECTROCHEM SC
Silicon based solar cells have been fabricated for single layer SiO2 and double layer SiO2/TiO2 antireflective coatings (ARC) using rf sputtering technique. The results were obtained with non-texturized surface of p-type mono-crystalline silicon (100) substrate and compared with the as-grown Si solar cell. Effect of single layer (SLAR) and double layer (DLAR) AR coatings on the performance of solar cell were characterized through electrical (AM 1.5G, 100 mW/cm2), optical and morphological measurements. The addition of the DLAR initiated 37% improvement in the efficiency of the mono-crystalline Si solar cells, compared with 4.5% of the SLAR Si solar cell. Morphological and optical measurements were carried out by atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), Raman spectra and reflectance spectra. A reflection spectrum of DLAR was also measured which shows the minimum reflection of 2.3% at 630 nm with an average reflection of 7% (within the 400-1000 nm range). The results indicated that the DLAR SiO2/TiO2 coatings could be valuable in achieving highly absorbent surfaces in optoelectronic devices as well as in the production of high efficiency low cost silicon solar cells.
View
Design and fabrication of multi-layer antireflection coating for III-V solar cell
Article
  • May 2011
  • CURR APPL PHYS
ZnS and ZnS–MgF2 composite films were prepared on soda-lime glass substrates and MgF2 films on GaAs by rf magnetron sputtering to investigate multi-layer antireflection (AR) coatings. Optical constants of these films were determined by envelope method and spectroscopic ellipsometry. In particular, ZnS–MgF2 composite films were fabricated by co-sputtering of ZnS and MgF2 target to obtain intermediate refractive index material for a middle layer in the triple-layer AR coating and these films exhibited the desired intermediate refractive index. Based on the extracted optical constants, single-, double- and triple-layer AR coatings on GaAs substrates were designed and fabricated by rf magnetron sputtering. Low reflectance could be obtained from single-layer AR coating only at a specific wavelength and could be obtained from multi-layer AR coating at wide wavelength regime. Additionally, incident angle dependence of the reflectance of the multi-layer AR coatings was also investigated and showed different behavior according to a number of layers.
View
Rajabi Efficiency Enhancement of Si Solar Cells by Using Nanostructured Single and Double Layer Anti-Reflective
  • Jan 2013
  • 365-369
  • M Moradi
M. Moradi, Z. Rajabi Efficiency Enhancement of Si Solar Cells by Using Nanostructured Single and Double Layer Anti-Reflective Coatings JNS 3 (2013) 365-369.