19. Multilayer Multi Material Solar Photovoltaic Cell for Near Cent Percent Efficiency

Abstract

A multilayer solar cell, with multiple materials is designed for near cent per cent efficiency. This design is pending fabrication since 1992 due to lack of facilities.

1. Introduction

The highest efficiency of the solar photovoltaic cell achieved by any material till now is about 16% by Silicon. This extremely poor efficiency makes the solar panels large in size and not usable for mobile and similar applications apart from the higher cost involved in making such large panels. To overcome this difficulty a near cent percent multilayer solar cell with multiple materials is designed. I got this idea in 1992 only but its fabrication is delayed due to lack of facilities.

2. The design of the multilayer near cent percent efficient solar cell

It is well known that different materials have different band gap energies and each material absorbs photons of a particular energy equal to its energy gap to convert it into electrical energy. The solar cell on the other hand consists of photons of all energies. This is the reason for the poor efficiency of the cell made of one particular material like Silicon having the energy gap of about 0.6V and Titanium Oxide having an energy gap of about 4V. By using multiple materials the efficiency will increase since the photons of a particular energy only are absorbed by one material and all the other photons will pass through that material. For example the thin layer of Titanium Oxide is transparent to the visible spectrum and naturally to infrared spectrum in which the energy gap of Silicon lies. It is also well known in general that thin layer of any material is transparent and there are even antireflection thin layer films fabricated and tested. Hence by using many or all the possible materials in different partially transparent layers in a single photovoltaic cell it is possible to achieve near cent per cent efficiency.

Let us now discuss about interconnection requirement of such layers. Since each cell produces different voltage all the cells have to be connected in series. It may also be possible that a particular cell may not withstand the current produced by other cells. Such a case either the size of the cell has to be increased to withstand more current or more than one cell of the same material have to be connected in parallel.

3. Fabrication

The fabrication of these devices is not difficult by the present day integrated circuit, thin film fabrication and the mechanical panel mounting technologies available now. They can be fabricated by nanotechnology also to reach nearest to Cent Percent efficiency. Even better technologies can be developed as the volume increases.

4. Conclusions

Since the solar energy is freely available for billions of years and it is a huge source of energy these high efficiency small size devices will have profound impact in the energy sector. Their urgent fabrication is utmost important and should be taken up fast.