Research Status of Organic Photovoltaic Cells

1
Research Status of Organic Photovoltaic Cells
2
History of organic photovoltaic cells

• Photovoltaic effect refers to the phenomenon in
  which a potential difference is generated between
  different regions of a semiconductor or a
  combination of semiconductors and metals that are
  illuminated by light. The term "photo-voltaic"
  appeared in English in 1849, which means that
  electromotive force is generated by light, that
  is, light generates volts. With the gradual
  understanding of the physical properties of
  semiconductors and the advancement of processing
  technology, in 1954, researchers from Bell
  Laboratories in the United States discovered that
  when silicon was doped with a certain amount of
  impurities, it became more sensitive to light.
  The first solar cell with practical application
  value was born in Bell Laboratories in 1954,
  marking the arrival of the era of solar cells.

3
Basic principles of organic photovoltaic cells

• The basic principle of organic photovoltaic cells
  is similar to inorganic solar cells
• (1)After a certain amount of light is irradiated
  to an organic photovoltaic device, a photon
  having energy is absorbed by the organic
  semiconductor layer, and an electron is excited
  to transition from the valence band to the
  conduction band, leaving a vacancy at the valence
  band. This vacancy called holes and the holes
  have a positive charge.
• (2)In conventional semiconductors, the excited
  electrons and formed holes move freely toward the
  opposite electrode. In conductive polymers, the
  electrons and holes formed by the excitation of
  incident photons will exist in a bound form, that
  is, they become excitons.
• (3)Usually these electron holes are formed when
  excited by photons. If they are in the electric
  field or at the interface, these electron hole
  pairs will be separated into electrons and holes,
  which are called charged carriers. Photocurrents
  are formed during the migration of charged
  carriers.

4
Classification of organic photovoltaic cell
materials

• According to mechanical properties and
  processability, organic photovoltaic cell
  materials can be divided into insoluble
  materials, soluble materials, and liquid crystal
  materials. These materials usually include small
  molecules or oligomers, polymers, and liquid
  crystal molecules. Among them, oligomers or
  monomers capable of absorbing visible light are
  called chromophores, those with solubility are
  called dyes, and those without solubility are
  called pigments. At present, the polymer
  materials used in photovoltaic device research
  mainly include polythiophene (PTH) derivatives,
  polyphenylacetylene (PPV) derivatives,
  polyparaphenylene (PPP) fluorene derivatives,
  polyaniline (PANI) and other polymer materials.

5
Advantages of organic photovoltaic cells

• Compared with inorganic solar cells, organic
  solar cells have the following advantages
• (1)Compared with the materials used for inorganic
  solar cells, the raw materials of organic
  semiconductor materials are widely available,
  cheap, light weight, high environmental
  stability, and have a high absorption coefficient
  (usuallygt 105cm-1) and good photovoltaic effect.
• (2) The preparation process of organic solar
  cells is more flexible and simple. It can be
  prepared by vacuum evaporation, coating, printing
  or spraying. The energy consumption of organic
  solar cells in production is lower than that of
  inorganic materials, and the production process
  has no environmental pollution. Organic solar
  cells can be processed on flexible or
  non-flexible substrates, and have the
  characteristics of large manufacturing area,
  ultra-thin, cheap, good flexibility and so on.
• (3) Organic solar cell products are translucent,
  easy to decorate and use.

6
Application prospects of organic photovoltaic
cells

• As fossil energy is limited and non-renewable,
  finding an alternative energy source has become
  an important task to maintain the sustainable
  development of the global economy. Photovoltaic
  power generation directly converts solar energy
  into electricity, which is a green renewable
  energy source with high commercial development
  value. And it is expected to become one of the
  main energy sources at the end of this century.
  With the continuous improvement of photovoltaic
  cell manufacturing technology and the continuous
  rise in the price of fossil energy, the
  photovoltaic power generation industry has
  entered a stage of rapid development. The
  international community is also increasingly
  optimistic about the development prospects of the
  photovoltaic power generation industry. The
  International Energy Agency (IEA) predicted in
  the solar photovoltaic roadmap published in May
  2010 that the proportion of photovoltaic power
  generation in total global electricity will reach
  1.3 in 2020 and rise to 4.6 in 2030.

7
Conclusion

• The current research direction of photovoltaic
  cells is to develop efficient and low-cost
  battery materials and manufacturing technologies.
  Organic polymer photovoltaic cells use conjugated
  polymer as the photovoltaic material, and the
  manufacturing process is simple, the cost is low,
  and they can be manufactured on a large area,
  which makes the research of organic polymer
  photovoltaic cells more and more important.
  Although the research of polymer photovoltaic
  cells has made remarkable progress in recent
  years, its photoelectric conversion efficiency is
  still very low. Only by obtaining highly
  efficient and stable photovoltaic cells can the
  commercialization of polymer photovoltaic cells
  be achieved. The improvement of the efficiency of
  organic polymer photovoltaic cells can be
  achieved through the selection of materials and
  optimization of the structure of photonic and
  optical devices.