Modern organic solar cells are an example of one of the most promising technologies for converting solar energy. The main areas where it is used today are consumer electronics, residential and commercial sectors, and the defense industry.
Experts predict that the market size of such photovoltaics in 2021 will amount to more than 2.5 billion USD. Over the past 5-6 years, more and more organic-based products have appeared. These include not only flexible films, but also awnings, translucent awnings, umbrellas, tents, bags, light-converting fibers, fabrics and others.
Organic solar cells – structure, types and materials
All promising organic photovoltaic panels described in various sources are divided into two main types.
1. “Layered”, in which the active components are applied to the substrate in separate layers. As you can see in the photo (type “a”), the structure of an organic “layered” solar battery is shown as an example. Its composition is separate films based on copper / indium / gallium / selenium diselenide (CIGS).
The progressive method of applying CIGS is a printing method based on the use of a suspension of metal oxide particles – “ink”. Taking into account the viscosity, depending on the size of the particles and their concentration, it is possible to use the method of screen printing or inkjet deposition.
2. “Hetero-junction” (type “b”). This type of organic solar cells is a panel made of a mixture of graphene and polymer with a conventional heterojunction. Their structure contains only one photoactive layer, which is a mixture of a fullerene “donor” and a polymer “acceptor”.
The first option is most in demand by the aviation, space and defense industries, due to the higher efficiency, which today reaches 25-27%. The second option promises to be a real breakthrough for land-based commercial and residential use due to its low cost and ease of implementation.
Characteristics, merits and prospects
The most important characteristics of the third generation of photovoltaics are:
- thickness of about 1 mm;
- high strength and resistance to external factors;
- ease of application to all types of materials;
- the ability to quickly manufacture on infinitely long strips – the so-called roll organic solar panels;
- different light transmittance, up to almost complete transparency;
- extremely light weight;
- ecological safety for the environment and the health of others.
Currently, research and development of new organic solar cells is most intensively carried out in the USA, Germany, Japan, China and Russia. The main direction of work is the creation and improvement of materials for their manufacture. The ultimate goal is to make the sun-absorbing elements:
- more efficient;
- multifunctional,
- fast and easy to manufacture;
- with the longest possible service life;
- lightweight and cheap;
- varied in shape.
Applications
There are already more than a dozen of them.
- A number of companies offer to buy translucent and transparent organic solar cells made of graphene that can be applied to the outside of window panes. This allows you to simultaneously solve two problems – to maintain the level of light transmission and to generate electricity.
- Another interesting proposal is photovoltaic cells in the form of durable fabric fibers. Experts predict that after just 7-10 years any fabric can be turned into a source of electricity. In the meantime, they are beginning to be woven en masse into clothes, shoes, bags and other popular accessories.
- The next promising direction is the transition from silicon to organic solar cells for cars and aircraft. You can buy such types of transport in many countries of the world.
- This type of photovoltaics will definitely come to the field of automobile, boat and hiking tourism. During long hikes, trips or river rafting, organics showing very high efficiency in low light conditions are indispensable.
Improving the performance of organic batteries
So far, roll-to-roll organic solar cells are inferior to the “classics” in terms of efficiency. To change this trend, engineers find different ways, of which two are more common.
Method # 1 – Tandem cells
One of the problems of “solar” organics is weak molecular bonds. Scientists have found a solution in creating tandem cells, each layer of which consists of different types of organic materials and absorbs different wavelengths.
The leader in the development of this area is the Chinese physicist Chen Yong Shen and his group. According to the professor, the productivity of photovoltaic cells of this class can increase by 30-40% in 3-4 years.
Method # 2 – solar cells based on organic dyes from bacteria with altered DNA
The Canadians were the first to use bacteria with a modified genome. Since 2018, they have been experimenting with E. coli microorganisms, known for their ability to produce lycopene.
Biochemists at the University of Toronto have been able to incorporate bacteria into a semiconducting mineral powder. When placed on a substrate, such “biogenic” elements began to give current due to their vital activity.
So far, solar cells based on organic dyes have not become widespread. But their important advantage is, in theory, an almost infinite lifespan. After all, many generations of bacteria will constantly replace each other, and under the right conditions, a colony on a substrate can live and give a current for an arbitrarily long time.
The record for the efficiency of the current photo of organic matter is 25% – and with an ultra-low illumination of only 220 lux (an analogue of a rather dark room). The developers of the novelty are CEA (France) and Toyobo Co., Ltd (Japan).