ORGANIC PHOTOVOLTAIC CELLS

 

  ORGANIC PHOTOVOLTAIC CELLS

Name – Poushali Gope, PG Student,

Department of Renewable Energy

Organic photovoltaic cell research has developed during the past 30 years, but especially in the last decade it has attracted scientific and economic interest triggered by a rapid increase in power conversion efficiencies. This was achieved by the introduction of new materials, improved materials engineering, and more sophisticated device structures. Today, solar power conversion efficiencies in excess of 3% have been accomplished with several device concepts. Though efficiencies of these thin-film organic devices have not yet reached those of their inorganic counterparts the perspective of cheap production (employing, e.g., roll-to-roll processes) drives the development of organic photovoltaic devices further in a dynamic way.

Though common materials used for photovoltaics (i.e., the conversion of sunlight into electrical energy) are inorganic, there has been a tremendous effort to develop organic photovoltaic cells within the last three decades. The field started by the application of small organic molecules (pigments) and since the development of semiconducting polymers. These materials were incorporated into organic photovoltaic cells resulting in remarkable improvements within the past years.

Some of the organic materials used are –

1. CN-PPV (Cyano polyphenylene vinylene) 2.PPV (Phenylene vinylene) 3.Pthalocycnine

1.      MEH-PPV(Poly[2-methoxy-5-(2- ethylhexyloxy)-1,4phenylenevinylene).

2.      Organic Photovoltaic Cells can be classified as: 1. Single layer organic cells.

a.       Bilayer organic cells.

b.      Bulk heterojunction organic cells.

There are Two types of donor – 1. HOMO (Highest Occupied Molecular Orbit) also known as the Valence Band.

   2. LUMO (Lowest Unoccupied Molecular orbit) also known

as the Conduction Band.

When the Organic layer absorbs the sunlight, electrons will be excited to the LUMO and leaves holes in the HOMO, thereby forming excitons. Because sunlight energy much higher than Egap energy. That’s why HOMO creates a hole, electron jumps from HOMO to ITO that is called Anode. The negative charges that present in LUMO that are called excitons. After that negative electrons jumps from LUMO to acceptor’s LUMO, because of donor energy level is higher than acceptor energy level. And negative electron jumps to metal that is called Cathode. The current and voltage resulting from this process can be used to do useful work.

 

Organic semiconductor devices in general and organic photovoltaic cells in particular can be integrated into production lines of packaging materials, labels, and so forth. Because there is a strong development effort for organic electronics integration into different products worldwide, the solar powering of some of these products will be desired. The next generation of microelectronics is aiming for applications of “electronics everywhere,” and such organic semiconductors will play a major role in these future technologies. Combinations of organic solar cells with batteries, fuel cells, and so forth, will enhance their product integration. This integrability of organic photovoltaic cells into many products will be their technological advantage.