anti reflective coatings on the solar photo voltaic panel's
PRESENTED BY :-
RAJNEESH KUMAR GAUTAM
M-TECH (ENERGY AND ENVIRONMENT)
IN THE EXPERT GUIDANCE OF :-
VIJAY K. JAISWAL
ASSISTANT PROFESSOR (GUEST)
BBA UNIVERSITY -LUCKNOW
In typical installations,
approximately 4% of incoming
light is reflected off the face of
the PV module and is lost.
What is antireflective coating ?
Antireflective or anti-reflection (AR) coating is a type of optical
coating applied to the surface of lenses and other optical devices to
reduce reflection.This improves the efficiency of the system since
less light is lost.
Antireflection is achieved by destructive interference between
For destructive interference Δ = (2m+1) λ/2
2nd = (2m+1) λ/2 => d = λ/4nc = λ’/4
d = minimum required thickness of coating
λ’ = wavelength in coating medium
About 4% of the light hitting the glass of a solar modules is reflected and thus
lost for electricity production.
Reflections can be reduced and thus light transmission can be increased by
using antireflective (AR) coatings.
The higher electricity output results in a reduction of the cost per panel.
‘Traditional’ AR coatings are either expensive or have to compromise on the
balance optical vs mechanical properties.
Why use anti-reflective coatings on
solar cover glass?
Solid silica particles
Modern Coat™ AR coating
Chemical vapour deposition
Physical vapour deposition
Formation of antireflection coating
Plasma enhance chemical vapour deposition
Low temperature treatment
More corrosion resistant
Can coat complex shapes
Hard particles can be
incorporated to increase
Can coat most metals and
More expensive than
Heat treatment is needed to
develop optimum properties
Thin compound layers can
be produced by reacting a
metal surface with an
acidic solution. e.g. Thin
(10mm) coatings of metal
phosphates are formed on
steel substrates exposed to
phosphoric acid. These
provide low friction
Cheap and simple to
Restricted range of materials
can be treated
Thin treated layer
Poor treatment durability
Difficult to control treatment
quality on heterogeneous
PHYSICAL VAPOUR DEPOSITION
A variety of vacuum deposition
Purely physical process , no
chemical reaction involved.
Process involved three steps:
multiple coating layers possible
MgF2 coating on glass
Almost any type of inorganic material can be
used as well as some kinds of organic materials.
The process is more environmentally friendly
than processes such CVD.
Advantages of PVD
High capital cost
Equipment size large because vacuum required
Processes requiring large amounts of heat require
appropriate cooling systems
The rate of coating deposition is usually quite slow
CHEMICAL VAPOUR DEPOSITION
Gaseous compounds react to form a dense layer on
a heated substrate. The most widely deposited
wear-resistant coatings are TiC, TiN, chromium
carbide and alumina. Deposition temperatures are
generally in the range 800-1000C which restricts
the range of materials which can be coated and can
lead to component distortion. Thicknesses are
limited to about 10mm due to the thermal
expansion mismatch stresses which develop on
cooling which also restrict the coating of sharp
Layer deposition involves chemical reactions
Large density films
Good stoichiometry & uniformity over large surface area.
SiO2 SiN, SiON, SiOC , and TiO2 with proper thickness are
the common AR material deposited chemically.
Required high temp to produce high quality material and for
many application the substrate cannot tolerate being heated
so not useful in that case .
High coating hardness
Good adhesion (if the coating is not too thick)
Good throwing power (i.e. uniformity of coating)
High temperature process (distortion)
Sharp edge coating is difficult (thermal expansion
Limited range of materials can be coated
Environmental concerns about process gases
Combined process of both CVD and PVD
a process used to deposit thin films from a gas state (vapour)
to a solid state on a substrate.
Chemical reactions are involved in the process, which occur after
creation of a plasma of the reacting gases
The plasma is generally created by RF (AC) frequency or DC discharge
between two electrodes, the space between which is filled with the
Processing plasmas are typically operated at higher pressures
PLASMA ENHANCED CHEMICAL VAPOUR DEPOSITION
of a few millitorr to a few torr , although arc discharges and
inductive plasmas can be ignited at atmospheric pressure
Plasma enhanced CVD is most useful because it can deposit layers on fragile
substrates that cannot withstand the high temperatures of other CVD
Plasma enhanced CVD systems allow for greater control of the film
composition, density, and film stress.
Higher deposition rate at low temperature relatively
Plasma can cause damage to the substrate surface when either secondary
electrons collide with the wafer surface or the energy of the ion bombard-
ment becomes too high.
Advantages of PECVD
How much reflection while using AR coating ?
Can be reduced up to ~ 0.2%
APPLICATION OF ANTIREFLECTION COATING
Anti-reflection coated optical windows
Reflex free sight glasses
Laser scanner windows
Anti glare coated instrument windows
Low reflection camera windows
Antireflection coated glass for displays
In microelectronic photolithography to
reduce image (substrate) distortions .
solar cell with SiO coating
Glass with MgF2 coating
TESTING OF ARC SURFACE
SAND BLAST TESTING
Figure 2: Surface defects post sand blasting
showing scratches on ARC glass and
of the uncoated glass