Category: SOLAR PANEL

When sunlight hits the solar cell, the energy of the absorbed photons is transferred to the electrons in the silicon. This energy heats the electrons, enabling them to overcome the barrier between the n-type and p-type layers, creating an electric current. 

Regardless of their application, be it in a central power station, a satellite, or a calculator. Solar cells share a common structure. Light penetrates the device through an optical coating or anti-reflection layer, which minimizes light loss due to reflection.  

This layer effectively captures the light hitting the solar cell by facilitating its transmission to the energy-conversion layers beneath. The anti-reflection layer is usually a silicon, tantalum, or titanium oxide applied to the cell surface through spin-coating or vacuum deposition. 

Beneath the anti-reflection layer are three energy-conversion layers: the top junction layer, the absorber layer (the device’s core), and the back junction layer.  

Two additional electrical contact layers are required to transport the electric current to an external load and back into the cell, completing an electric circuit.  

The electrical contact layer on the light-entering face of the cell is typically in a grid pattern and made of a good conductor like metal.  

As metal obstructs light, the grid lines are as thin and widely spaced as possible without compromising the collection of the cell-produced current. 

The back electrical contact layer, which only needs to function as an electrical contact, covers the entire rear surface of the cell structure. Since this layer also needs to be a good electrical conductor, it is always made of metal. 

Given that most of the energy in sunlight and artificial light is in the visible range of electromagnetic radiation, a solar cell absorber should efficiently absorb radiation at these wavelengths.  

Materials that absorb visible radiation well are known as semiconductors. Semiconductors, even in thicknesses of about one-hundredth of a centimetre or less, can absorb all incident visible light.  

Since the junction-forming and contact layers are much thinner, the thickness of a solar cell is essentially that of the absorber. Examples of semiconductor materials used in solar cells include silicon, gallium arsenide, indium phosphide, and copper indium selenide. 

When light hits a solar cell, electrons in the absorber layer are excited from a lower-energy “ground state” to a higher “excited state,” allowing them to move through the solid.  

Without the junction-forming layers, these “free” electrons move randomly, preventing any oriented direct current. However, the addition of junction-forming layers creates a built-in electric field that generates the photovoltaic effect.  

Essentially, the electric field directs the electrons to flow past the electrical contact layers into an external circuit where they can perform useful work. 

The materials used for the two junction-forming layers must differ from the absorber to create the built-in electric field and carry the electric current.  

Therefore, these could be different semiconductors or a metal and a semiconductor. The materials used to build the various layers of solar cells are similar to those used to produce diodes and transistors in solid-state electronics and microelectronics.  

Solar cells and microelectronic devices share the same basic technology. However, in solar cell fabrication, the aim is to build a large-area device because the power produced is proportional to the illuminated area.  

In contrast, microelectronics aims to construct ever-smaller electronic components to increase their density and operating speed within semiconductor chips or integrated circuits.