Transparent photovoltaic film: a solar innovation

Transparent photovoltaic film is an innovative technology that generatessolar energy while retaining the material’s transparency and lightness. This could lead to innovative applications that promote the development of renewable energies (ENR). This promising solution is being developed by a number of companies, including Armor, which markets a product called ASCA. This article presents the technology, its applications and the companies pioneering the field.

Transparent photovoltaic film technology

Transparent photovoltaic films are based on organic photovoltaic (OPV) cell technology, which uses organic semiconductor materials, unlike traditional silicon-based photovoltaic cells. These organic materials are generally polymers or small molecules that can be deposited in thin layers on a variety of substrates, such as glass or flexible plastic films.

The basic principle of light-to-electricity conversion in OPVs is similar to that of inorganic photovoltaic cells. When sunlight strikes the organic semiconductor material, light energy is absorbed, generating pairs of electrons and holes (excitons). These excitons migrate to the junction area between the donor and acceptor materials, where they separate to form free charges. The electrons then move towards the negative electrode, while the holes move towards the positive electrode, creating an electric current.

Transparent photovoltaic films generally have a sandwich structure made up of several layers, including :

1. Substrate : This layer serves as a support and can be made of flexible or rigid materials, such as glass or plastic.
2. Transparent conductive layer: This layer ensures electrical conductivity while allowing light to pass through the film.
3. Active layer : This is the heart of the device, where organic semiconductor materials absorb light and generate excitons.
4. Buffer layer: This layer facilitates charge separation and improves cell efficiency.
5. Electrode : The electrode collects the separated electrical charges and transfers them to the external circuit.

One of the main challenges facing transparent photovoltaic films is to optimize transparency while maintaining acceptable energy efficiency. Researchers are exploring various approaches to improving the performance of OPVs, including developing new organic semiconductor materials, optimizing the optical and electrical properties of transparent conductive layers, and designing more efficient cell architectures.

Advantages and disadvantages of transparent photovoltaic films

Transparent photovoltaic films, based on organic photovoltaic (OPV) cell technology, offer a number of advantages and disadvantages over traditional photovoltaic cells, such as those based on silicon.

Advantages

1. Lightweight and flexible : The organic materials used in OPVs enable the creation of lightweight, flexible films, making them easy to transport, install and integrate into a variety of applications, such as windows, building facades and portable electronic devices.
2. Transparency : Transparent photovoltaic films can be designed to let through a large proportion of visible light, enabling them to be used in applications where transparency is essential, such as building glazing or the screens of electronic devices.
3. Low-temperature manufacturing: OPVs can be manufactured at relatively low temperatures, reducing the energy costs and carbon emissions associated with their production.
4. Roll production: Transparent photovoltaic films can be produced in rolls, enabling large-scale production and reducing manufacturing costs.
5. Aesthetic integration: Transparent photovoltaic films can be easily integrated into the architecture and design of buildings or products, without altering their appearance.

Disadvantages

1. Lower energy efficiency : OPVs generally have lower energy efficiency than traditional silicon-based photovoltaic cells. Research is ongoing to improve the efficiency of organic photovoltaic cells.
2. Lifespanand stability: Transparent photovoltaic films have a shorter lifespan than silicon photovoltaic panels, due to the sensitivity of organic materials to degradation by moisture, oxygen and sunlight. Progress is being made to improve the durability and stability of transparent photovoltaic films, notably by developing better sealing barriers and optimizing the organic materials used.
3. Cost : Although the production costs of OPVs may be lower than those of traditional photovoltaic cells, the current costs of transparent photovoltaic films can still be relatively high due to the limited scale of production and the need to improve materials and manufacturing processes.
4. Sensitivity to angle of incidence: Transparent photovoltaic films can be more sensitive to the angle of incidence of sunlight than traditional photovoltaic cells, which can affect their performance depending on the orientation and location of the installation.

Projects, companies and products

Leading companies and products

A number of companies and projects are involved in the development and marketing of transparent photovoltaic films, mainly based on organic photovoltaic (OPV) cell technology. Here are some of the notable companies and projects in this field:

1. Armor Group (ASCA): Armor Group is a French company that has developed flexible, lightweight organic photovoltaic films under the ASCA brand. Their products are designed to be integrated into a variety of applications, such as buildings, vehicles and portable electronic devices.
2. Heliatek is a German company specializing in the production of transparent organic photovoltaic films. They are working on various projects and partnerships to integrate their OPV technology into building glazing, facades and roofs.
3. SolarWindow Technologies (US) develops transparent photovoltaic films that can be applied to glass surfaces to generate electricity from sunlight. Their technology is intended for use mainly in commercial and residential buildings.
4. Ubiquitous Energy is a US company developing transparent photovoltaic films for glazing and electronic device display applications. Their technology, called ClearView Power, is designed to convert sunlight into electricity while allowing visible light to pass through.
5. Onyx Solar is a Spanish company specializing in building-integrated photovoltaic (BIPV) solutions. They offer transparent photovoltaic films for windows, roofs and facades.

Notable projects

1. The city of La Rochelle worked with Armor Group to install ASCA transparent photovoltaic films on the city’s bus shelters, transforming these structures into sources of renewable energy. JCDecaux, world leader in outdoor advertising, is working with Armor to integrate transparent solar films into its bus shelters and billboards.
2. Google has invested in the research and development of transparent photovoltaic films for use in the glazing of buildings on its California campus.
3. Masar Printing, based in the United Arab Emirates, has integrated transparent photovoltaic films into the glazing of its headquarters, saving energy while providing solar protection.

Future challenges and issues