Research

Organic Solar Cells – Evolutionary Technology Empowering Lives

Divesh Kubal elaborates the phenomenon of the organic solar cells – an electrical device that converts the light energy directly into electricity by the photovoltaic effect, which in turn, is a physical and chemical phenomenon. 

He specifies the perks of such organic solar cells, in terms of utility in the various gadgets and other forms of machinery of importance, and also explains the structure of a bilayer organic photovoltaic device.

 

A traditional solar cell, or also called as a photovoltaic cell, is an electrical device that converts the light energy directly into electricity by the photovoltaic effect [1]. Photovoltaic effect is a physical and chemical phenomenon. Solar cells are the building blocks of photovoltaic modules, otherwise known as solar panels. Solar cells are also described as being photovoltaic where the source of light can be sunlight or an artificial light. The biggest limitations of traditional solar cells are that they are very much expensive, not processed abundantly because the raw materials are rare on mother Earth[2]. 

We have come up with a new emerging technology called as organic solar cells. Most importantly they can be made available abundantly on Earth. This in turn will reduce the consumption of traditional fossil fuels, less pollution, less ill-effects to Earth leading to brighter and greener future.

Keywords: Organic solar cell, electron and hole, photovoltaic.

INTRODUCTION

Organic solar cells, also called as Organic photovoltaic (OPV) solar cells, have the primary aim to provide a low-energy-production photovoltaic (PV) solution which is available in abundance on Earth. As compared to traditional solar cells, this technology provides energy at a much lower cost.  Also, this technology is particularly appealing to the building-integrated PV market because various absorbers can be used to create colored or transparent OPV devices [1]. Organic solar cells have efficiencies near 11%, but they have limitations in efficiency and long-term reliability barriers.

Organic solar cells use molecular absorbers resulting in localized exciton. The resulting exciton migrates to the interface between the absorber material upon absorbing a photon. The exciton is splitted and free charge is created (electron and hole) at the interface due to the energetic mismatch of the molecular orbitals.

The low efficiencies of organic solar cells is due to their small exciton diffusion lengths and low carrier mobility which results in the use of thin active layers that affect overall device performance[3]. Also, the operational lifetime of organic solar cells remain much shorter than their inorganic counterparts. Currently research is going on to improve efficiency and lifetime of organic solar cells.

 

ORGANIC SOLAR CELLS

Organic solar cells are the devices which convert solar energy to electrical energy. A typical organic solar cell device consists of one or more than one photoactive material sandwiched between two electrodes[4]. We can take an example of a typical bilayer organic photovoltaic device to explain the concept of organic solar cell.

Figure 1 depicts a basic typical bilayer organic photovoltaic device. In a bilayer organic solar cell, sunlight is absorbed in the photoactive layers which are  composed of donor and acceptor semiconducting organic materials to generate photocurrents. The donor material (D), as the name suggests, donates electrons and important function is to transport holes and the function of the acceptor material is to withdraw electrons and to mainly transports electrons.

 

Figure 1: Structure of a bilayer organic photovoltaic device

The photoactive materials harvest photons with the help of sunlight to form excitons, in which the electrons are excited from the valence band into the conduction band (Light Absorption). Then the excitons diffuse to the donor/acceptor interface and separate into free holes and electrons because of the concentration gradient. As a result, the photovoltaic is generated when the holes and electrons move to the corresponding electrodes.

 

ESTIMATION OF COST TO SETUP

The manufacturing cost for purely organic solar cells will be in the range between rs.3000 and rs.8400/m2. Assuming the efficiency of 5%, we get cost of a module between rs.60 and rs.170. A 5 year lifetime for organic solar cell is assumed.

 

BENEFITS

There is lot of benefits of using organic solar cells.

One important benefit is low cost to manufacture organic solar cells because of soluble organic molecules [1,2,3]. The materials needed to construct organic solar cells are abundant in nature which further reduces cost. 

The last benefit is the ability to apply flexible substrates, which in turn promotes wide variety of uses.

 

CONCLUSION

Hence, by doing considerable research on organic solar cells, one can solve the only limitations of organic solar cells i.e. efficiency and lifetime limitations. Once we solve these two limitations, then there will be a time when entire mankind will solely depend on solar energy for their day to day energy uses. This will lead to cleaner and greener Earth – Our Motherland.

 

REFERENCES

[1]  CW Tang – US Patent 4,164,431, 1979 – Google Patents 

[2] Y Hashimoto – US Patent 4,963,196, 1990 – Google Patents 

[3] M Hiramoto, H Fujiwara, M Yokoyama – Applied physics letters, 1991 – scitation.aip.org 

[4] YJ Cheng, SH Yang, CS Hsu – Chemical reviews, 2009 – ACS    Publications 

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