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Chapter
Transparent Solar PV Panels
TulshiShiyani
Abstract
Global warming is increasing emissions of greenhouse gases. It damages the
environment of Earth. Solar energy is the cleanest source of renewable energy. It is
an abundant source of clean energy. It has tremendous scope to generate electricity.
Solar cells are devices that convert solar energy into electrical energy. Transparent
solar panels are made up of transparent solar cells or transparent luminescent solar
concentrators. A transparency of about 80% has been achieved with power conversion
efficiency of about 12–15% in transparent solar cells. These cells can be used in
buildings, vehicles, and other desired applications to generate solar power. We discuss
solar energy basics and its conversion technologies. Transparent solar panels may
bring a revolution in low-power display devices and mobile applications.
Keywords: solar energy, solar cells, transparent solar panel, electrical energy
. Introduction
. Conventional solar panels
Solar energy is the cleanest source of renewable energy on earth. Solar cell works
on the principle of photoelectric effect that converts solar energy into electrical
energy. Solar cells are mainly categorized into four generations. The conventional
mono and polycrystalline wafer-based solar cells are first-generation [1, 2]. Thin
films solar cells such as CIGS, CdTe, and CZTS are second-generation of solar cells.
Multijunction solar cells are third-generation solar cells. Quantum dot and hybrid
solar cells are fourth generation of solar cells. Theoretically, each generation of solar
cells has energy conversion efficiency. Experimentally, multijunction solar cells have
achieved the highest energy conversion efficiency, about 47.5%. Silicon solar cells are
mostly commercialized technology due to abundant and cheap materials. However, its
fabrication involves expensive and toxic processes. Currently, solar panels are used as
off-grid and rooftop on-grid applications. Therefore, novel solar panel technology is
required for multiple applications such as windows, displays, surface, etc. [3–5].
. Transparent solar panels
A transparent solar panel is a basically challenging idea because sunlight (photons)
must be absorbed by solar cells and converted into electrical energy (electrons).
Sunlight can pass through the medium in transparent solar glass and it defeats the
conversion purpose. But in transparent solar panels, the absorption happens in a
Solar Panels - Recent Advances and Future Prospects
different way. The cell selectively harnesses a portion of the sunlight that is invisible
to naked eye and allows the visible light to pass through the device. The researchers
have developed the transparent luminescent solar concentrator (TLSC) to achieve
the transparent behavior of the cell rather than trying to develop the challenging
transparent PV glass cell [6, 7]. Transparent solar panels use transparent luminescent
solar concentrators as glass, which is transparent in nature. It uses organic molecules
to absorb invisible spectrum of sunlight. So, these organic molecules absorb the
specific IR and UV light. The electrons of molecules are excited by the energy of
radiation and jump to a higher-level orbit. When they settle at ground state, the
energy is released in the form of IR radiation (luminescent or glowing) of the
different non-visible spectrum. This emitted IR light is guided through the edge
of the plastic, where the strips of traditional solar cells convert it into electrical
energy. This technology is feasible on cars windows, buildings, mobile phones, and
other devices with a transparent surface. The limiting factor of this technology for
commercialization is its low efficiency of about 1%. However, efficiency can be
achieved by tuning the properties of the material in device. The first fully transparent
solar concentrator was built by researchers at Michigan State University in 2014. This
transparent solar panel could turn any glass sheet or window into a photovoltaic cell.
The full transparency was achieved for the solar glass by 2020. Transparent solar
panel technologies are set to transform the solar energy utilization landscape globally.
We may able to generate electricity from windows of building, vehicles, phones, etc.
These transparent solar panels can be deployed easily in various devices and systems
such as laptops, e-readers, skyscrapers, windows, etc. The glass windows in buildings
can be replaced by solar power windows [8, 9].
The organic salts absorb IR and UV light and emit IR in case processes occur
outside the visible spectrum. Thus it appears transparent. TLSC is composed of
organic salts that absorb specific UV and IR light, which then luminesce (glow)
as another invisible wavelength. This wavelength is then guided to the edge of the
window-thin PV solar cell strips that convert it into electricity. The mass production
of such transparent solar panels can give an efficiency of about 10%. This can help to
generate power through every window of home or office buildings and may bring a
transformative result [10].
Transparent solar panels are categorized into (i) partially transparent solar panels:
Heliatek Gmb, a German manufacturer has developed this technology that can absorb
60% of the sunlight it receives. They have achieved an energy conversion efficiency
of about 7.2%. However, the generation of solar power can be increased by adjusting
the transmitted and absorbed sunlight, for example, south-facing glass buildings
can reduce the transmitted light. (ii) fully transparent solar panels: The researchers
at MSU, USA have achieved fully transparent PV glass panels that resemble regular
glass. They have achieved energy conversion efficiency of about 10%. Bigger or more
windows can generate more solar power [11–13].
Currently, researchers at Michigan State University and MIT as well as manufac-
turers such as Brite solar, Physee, and Ubiquitous energy are pioneers in transparent
solar panel technology as shown in Figure . Ubiquitous energy has achieved energy
conversion efficiency of 9.8% and working toward developing net-zero energy
buildings [14, 15]. Physee has introduced power windows that work as building blocks
for smartskin. Smartskin can work for sensing, power generation, and regulating
the inside climate using an artificial intelligent system. Richard Lunt has proposed
making a solar cell that would absorb all the energy from the sun except the part that
allows us to see. He has developed highly transparent solar cells that represent the
Transparent Solar PV Panels
DOI: http://dx.doi.org/10.5772/intechopen.110062
wave of the future. He has claimed that these solar panels have similar power genera-
tion potential as rooftop. This can also be applicable to buildings, cars, mobile, and
other such devices. MIT researchers are developing transparent solar cells that could
turn every product such as windows and electronic devices into power generators.
These cells can absorb only IR and UV light. They have developed a room-tempera-
ture fabrication method and can deposit coatings of solar cells on various materials to
run electronic displays using ambient light [16–18].
Figure 1.
Vladimir Bulović of electrical engineering and computer science showing their transparent solar cells (upper),
and Richard Lunt demonstrates the transparency of the novel solar cell at MIT (lower).
Solar Panels - Recent Advances and Future Prospects
Solar Panel blinds are accessories to transparent solar glass or panels in case of
windows for generating electricity. This blocks direct sunlight from entering inside.
SolarGaps introduce solar blinds and claim that they can generate about 100W of
power on every 10 sq. ft. of window area. It can be installed from outside or inside and
can control its angle according to the sun’s position [19, 20].
. Device configuration of transparent photovoltaic device
The schematic representation of a transparent photovoltaic device is shown in
Figure . This shows the key component of transparent solar cell, which transmits
visible light and captures NIR and UV light. The thick layer is glass, plastic, or other
transparent material. The coating of PV materials on top of the device. These PV
materials are photoactive layers. The active layers include semiconducting materi-
als that get excited upon falling sunlight and interact, creating an electric field that
causes electric current to flow in a device through a circuit. This current can be taken
out of the device to an external circuit via connecting sandwiched electrodes. Both
electrodes must be transparent and they are anti-reflective coatings to reduce light
reflection. Therefore, a combination of optical design, molecular engineering, and
optimization of the device are used to design transparent PV devices [21].
Figure 2.
Schematic of transparent photovoltaic device.
Transparent Solar PV Panels
DOI: http://dx.doi.org/10.5772/intechopen.110062
. Spectral response of conventional and transparent PV cells
The spectral response of conventional and transparent solar cells is shown in
Figure . The absorptive response (black curve) is superimposed on the solar spec-
trum (gray curve). In the conventional cell, the wavelengths at which absorption
is relatively high include the visible spectrum (400–700nm). The transparent cell
absorbs well in the near-infrared and the ultraviolet spectrum but the absorption
drops off and approaches zero in visible range [22].
The current transparent solar cells transmit more than 70% of the visible light,
which is within the range of tinted glass used in the windows of buildings with a
Figure 3.
Spectral response for conventional (upper) and transparent PV devices (bottom).
Solar Panels - Recent Advances and Future Prospects
power-conversion efficiency of about 2%. Lunt and Bulović claimed that it can able to
reach over 12% efficiency on basis of theory. Lunt already has demonstrated transpar-
ent cells integrated into series can power the liquid crystal display on a small clock,
relying entirely on ambient light [23].
. Transparent flexible solar cells
A flexible transparent solar cell was first developed at MIT as shown in Figure .
Researchers have developed a novel technique using graphene to prepare solar cells on
surfaces of glass, plastic, paper, and tape. This device contains carbon-based organic
materials with graphene electrodes and transparent material. This device involves
a layer of graphene on the solar cell. The flexible transparent solar cells would be
lightweight and cheap technology as well as low-cost materials [23]. Organic materials
absorb the UV and IR components of the solar spectrum but transmit visible light.
The most affordable option is to use indium tin oxide (ITO) coated flexible substrate.
But ITO is brittle and may break during deposition on flexible substrate. A one-atom
thick layer of graphene can be developed as alternative to ITO in transparent solar
cells. This alternative material is flexible, highly conductive, and transparent. The
most important thing is that it is made up of inexpensive carbon material [24].
There are some problems during the deposition of graphene electrodes on solar
cells. The first problem is depositing 1 atom layer thick of graphene. A bottom layer of
graphene is deposited directly on the substrate and then the top layer. The fabrication
of graphene on the top layer in solar cells as a hole transport layer is very tricky. The
other main problem is preparing graphene electrodes for different applications. One
electrode should let electrons flow out easily in solar cells. So, here both graphene
electrodes have different work functions. Therefore, changing the work function is
not an easy task. A layer of ethylene-vinyl acetate (EVA) can be incorporated into
the graphene layer to make the device more flexible. This would differ both graphene
electrodes to work for different purpose [25].
In practical, a transparent solar cell was developed using graphene, ITO, and
aluminum materials. The performance of this solar cell was lower than solar cells with
one aluminum electrode. Aluminum electrode on the bottom reflects some incom-
ing light back into solar cell and increases the absorbance of sunlight more than a
Figure 4.
Transparent solar cell on flexible substrate developed at MIT.
Transparent Solar PV Panels
DOI: http://dx.doi.org/10.5772/intechopen.110062
transparent cell. The PCE for graphene/graphene devices was comparable to existing
commercial solar panels, about 4.1% with transparency of about 61%.
The organic solar cell has the advantage to deposit on any type of surface, such
as rigid or flexible, transparent, etc. The graphene/graphene devices have been
demonstrated on various flexible substrates such as plastic, opaque paper, translucent
kapton tape, etc. The performance was nearby in all these devices [26].
. Manufacturing of transparent solar panels
Polysolar is developing transparent solar panels for buildings, canopies, and
greenhouses applications. These panels can be used on walls with non-directional
ambient sunlight. They have installed transparent solar panels in some buildings and
bus shelters. This has allowed manufacturing of PV powering interactive displays,
lighting, and signage. They have achieved power conversion efficiency of up to 12–15%
in gray-tinted panels. Polysolar is trying to cover maximum area for generation of solar
power and increase the transparent PV footprint in various sectors [27].
Thin-film PV cells (in orange color) are deposited as a naturally translucent layer
onto the glass (blue) before another glass sheet is laminated on top as shown in Figure .
They allow the panels to work at a much higher efficiency at varying angles than regular
solar panels and can generate solar power at low levels of sunlight [28–30].
Ubiquitous energy is also developing transparent PVs using semiconductor with
higher efficiencies and transparencies. They are also trying to assemble panels on
electronic devices such as mobile phone display to self charge the devices.
. Conclusion
Transparent solar panels are very challenging to find their real time applications.
They have huge scope to generate solar power and making electronic devices for self
charging applications. Currently, they have limitations on large applications due to
low efficiency and cost. These solar cells can block the most of IR. Researchers have
Figure 5.
Thin-film photovoltaic cells (in orange) are deposited as a naturally translucent layer on to the glass (blue).
Solar Panels - Recent Advances and Future Prospects
Author details
TulshiShiyani
Saurashtra Research Institute, SRI, Rajkot, India
*Address all correspondence to: sh.ts@protonmail.com
developed graphene based organic solar cells with improved efficiency with signifi-
cant transparency. Increasing the amount of active area would push up the PCE, but
transparency would drop. The highest transparency of about 80% has been measured
in transparent solar cells with maximum power conversion efficiency of about
12–15%. The various materials have been utilized to improve the transparency and
performance of solar cells. Transparent solar panel would bring a remarkable change
in electronic and optical applications.
Acknowledgements
The authors are thankful to Shiyani Research Institute, Rajkot, and Shiyani
Enterprise (OPC) Private Limited, Rajkot for providing technical support to publish
this chapter.
© 2023 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of
the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided
the original work is properly cited.
Transparent Solar PV Panels
DOI: http://dx.doi.org/10.5772/intechopen.110062
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