Organic Solar Cells (OSCs)

                      Organic Photovoltaic cell (Source: Fraunhofer ISE)

Organic solar cells (OSCs), also known as plastic solar cells are third-generation photovoltaic technology using organic materials (carbon-based in the form of small organic molecules, dendrimers, and polymers), to convert sunlight to electrical energy.

Organic photovoltaic devices are comprised of one or several layers including a photoactive layer between two electrode layers. These layers are printed using roll-to-roll manufacturing, similar to the way newspapers are printed, with thicknesses on the nanometer scale. Photoactive layers are typically printed on a thin plastic substrate followed by lamination with a protective and flexible foil.

In an OPV cell, sunlight is absorbed in the photoactive layers composed of donor and acceptor semiconducting organic materials (typically either polymers or small molecules), to generate photocurrents. The donor material (D) donates electrons and mainly transports holes and the acceptor material (A) withdraws electrons and mainly transports electrons.

For organic materials to become conducting or semiconducting, a high level of conjugation (alternating single and double bonds) is required.

Organic solar cells have several advantages over their traditional silicon counterparts. They are very environmentally friendly because they contain no toxic elements and can be processed at low temperature using roll-to-roll deposition, so can have an extremely low carbon footprint.

Conventional silicon solar cells are perfect for large scale electricity generation in solar farms and on the roofs of buildings, but they are not suitable for the electric vehicles and integration into windows on buildings. Organic solar cells can sit on curved surfaces, they are very lightweight, flexible and transparent.

Additionally, manufacturing cost can be reduced for organic solar cells due to their lower cost compared to silicon-based materials and the relative ease of chemical synthesis.

Disadvantages associated with organic photovoltaic cells include their low efficiency (currently ~15%) in comparison with inorganic photovoltaic devices.

Organic solar cells are new types of flexible solar cells and they will become a commercial reality very soon because it will give the designers more choice in the materials they can use.

Transparent Solar Panels - Another Innovation in the Solar Technology

For about five years, scientists have been working on methods to develop transparent solar panels capable to convert the light that shines on them into electricity. Now this is reality.

In 2014 the team of scientist Richard Lunt from Michigan State University developed a transparent luminescent solar concentrator that looks just like a piece of clear glass, but which is covered in small organic molecules that can absorb specific invisible wavelengths of sunlight.

In their latest study, Lunt and his colleagues examined the efficiency of this kind of transparent solar tech, and estimate that if the see-through panelling can be scaled up to cover the estimated 5–7 billion square meters of glass surfaces throughout the US, it could potentially supply around 40 percent of American energy

This type of solar materials captures just ultraviolet and near-infrared wavelengths of light. The visible light that enables human vision isn't obstructed, which is why we can see through the cell.

Although, transparent solar panels are only 5 percent efficient compared to conventional solar panels with their 15–18 percent, they have great potential.

"Highly transparent solar cells represent the wave of the future for new solar applications," explains Lunt.

"We analyzed their potential and show that by harvesting only invisible wavelengths of light, these devices can provide a similar electricity-generation potential as rooftop solar while providing additional functionality to enhance the efficiency of buildings, automobiles, and mobile electronics."

The ultra-thin, transparent solar panels could be applied potentially onto skyscrapers and car windows, cell phones as well as other objects with a transparent surface. Which means that existing windows and screens would not need to be replaced in order to generate electricity from buildings or electronic devices.

Source: https://www.sciencealert.com/transparent-solar-cells-satisfy-40-of-american-power-needs-see-through-light

Solar-Powered School in Copenhagen

This is one more interesting news that represent another effort to be developed colored solar panels.

The International School in Copenhagen is using custom-built colorful solar panels as a featured architectural element. Each panel is individually angled and the result is really cool impression. The materials that were used in the new building are entirely natural. Thus the school made both an aesthetic and sustainable decision.

The campus of the cosy school is covered by 12,000 solar tiles making it the largest solar facade in the world. On sunny days the solar panels generate electricity that is contribute to the grid and to the school itself.

The solar panels are spanning over an area of 65,100ft2 and provide it with 300 MWh of electricity per year, meeting over half of the school's energy needs. One of the key vision of the school is to educate thair students of a sustainable world.

The unique building stands out because the panels are a distinctive sea green, the same of Copenhagen’s symbol - Andersen’ mermaid, which welcomes tourist in the Danish capital. Although no pigments were used to make them, the color comes from a process of light interference developed over more than a decade in the labs of the Ecole Polytechnique Federale in Lausanne (EPFL).

Based on a new technology developed in Switzerland the process that produced color of these panels is a similar to the effect seen in soap bubbles.

The researchers developed special filters, which they applied to the glass panels in nanometric layers. This filter determines which wavelengths of light will be reflected as visible color. The rest of the sunlight is absorbed by the solar panel and converted into energy.

“The iris effect creates a colorful rainbow on a very thin layer. We used the same principle and adapted for glass,  said Jean-Louis Scartezzini, the head of the Solar Energy and Building Physics lab at EPFL.

The school building won the 2017 Iconic Award - an international award program for architecture and urban planning professionals in the architecture category.

Green Colored Solar Panels

Highly rated models of solar panels are now running in excess of 20-percent efficiency at turning sunlight into electricity. But they are bulky and still aren't very pretty. In addition, traditional solar panels take up a lot of room.

Fortunately, solar technology is changing continuously. Earlier this year Tesla began selling solar shingles that can generate power for the home and still look like ordinary shingles. Other solar panel developers have made solar windows, skylights, patio covers, carports, and roads to generate electricity. And now researchers in the Netherlands say they have developed a process for making conventional bluish-black solar panels bright green. Probably the same technology might also make it possible to create panels in other colors, and even in white which would be a really big step in the solar industry. 

Researchers from AMOLF, the University of Amsterdam (UvA) and the Energy research Centre of the Netherlands (ECN) have developed a method for imprinting existing solar panels with crystalline silicon nanocylinders. The nanocylinders are about 100 nanometres wide and exhibit electromagnetic resonance that scatters a particular wavelength of light. They produce the green color by scattering green frequencies of light back while letting other frequencies of light pass through. They are laid down on the solar cells via a process the researchers likened to rubber stamping. The panels have a green appearance from most angles and they are only about 10 percent less efficient than conventional panels.

The method used for the colored solar panels is called soft-imprint lithography. “In principle, this technique is easily scalable for fabrication technology,” AMOLF scientific group leader and senior author Albert Polman said.

Such colored solar panels would afford a level of versatility - for example, red panels could be used on rooftops, white ones on walls, and the green ones could blend in with nature. Thus would encourage the reliance on solar energy and integration of solar technology into every part of our daily lives.

“You have to combine different nanoparticles, and if they get very close to each other they can interact and that will affect the color,” said Polman.

These aren't the first colored solar panels. But the ones already on the market use dyes and reflective coatings that give them their color, greatly reduce efficiency and they are about 45 percent less efficient than ordinary solar panels at generating electricity.

The new design was published online on August 15, 2017, in Applied Physics Letters.

Solar City Tower Waterfall for Rio Olympics 2016

Rio de Janeiro, Brasil, was selected for the 2016 Olympic Games and it is planning on building a massive solar powered artificial waterfall called "Solar City Tower", designed by Swiss (Zürich-based) company - RAFAA Architecture & Design.

The 344.5-foot tall (105 meters) Solar City Tower is going to be located on the small Cotonduba Island in Guanabara Bay. The enormous waterfall is almost twice the height of Niagara Falls and will be large enough to accommodate the opening and closing Olympic ceremonies. It is one of the first buildings that are being designed for the 2016 Rio Olympics.

This solar energy generating tower will be using many solar panels to produse electricity for the Olympic village by day. Any excess energy would be used to pump seawater into reservoirs at the top, so that it can be released by night as a spectacular waterfall. The falling water would also help turbines create electricity for the nighttime village.

In addition to producing energy, the Solar City Tower would have an elevator to take visitors to the very top of the tower, where a “glass sky walk” offers panoramic views of the surrounding harbor and Rio. There's even a platform at 297 feet (90.5) that provides bungee jumping. The giant tower would also house an auditorium, cafeteria, shop and amphitheater on the ground level.

The Solar City Tower is RAFAA’s entry in the International Architecture Competition for the 2016 Olympics, where the Brazilian metropolis aims to represent the green city of the future and hope to achieve its goal to host the first-ever zero-carbon Olympics.