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Solar Cells: A Quick Overview

By Jaspreet Kaur, PhD, Data Analyst


Introduction


A solar cell convert light from both solar and non-solar sources into electricity. The process is called photovoltaic (PV) effect and solar cell is a photovoltaic or PV device. Solar cell is one of the of the most important technologies for a green and clean future. Solar cells are mostly made of silicon material and have two generic types: Crystalline and thin film. The crystalline silicon solar cells are a just a palm size, often octagonal in shape and bluish-black in color. They are bundled into make larger units called solar panels. Solar systems installations on a roof or in solar farms can range from a few to thousands of solar panels. Solar cells can also be chopped into small chips for pocket calculators and digital watches.

A typical silicon solar cell

How does it work?


Solar cell is typically a p-n junction semiconductor device where p refers to high concentration of holes or shortage of electrons and n-type is an electron enriched region. The difference in electron and hole concentration induces the flow of charges from the n side to p-side in the depletion region within the device and from p-side to n-side in an external circuit to conduct electricity. Absorption of light on solar cell creates light generated current in two steps. First, the absorption of incident light or photons creates electron-hole pairs. The condition for this is that the light incident on the p-n junction should be greater than the band gap of the material. The band gap of a semiconductor is the threshold energy for the electron to get excited from its bound state into a free state where it can contribute in conduction. The electrons in the n-region and holes in the p-region are meta-stable and spatially separated by external electric field at the p-n junction to prevent them from recombination. The light generated minority carriers are then moved to their majority region by this external field and flow through the external circuit and generate electricity. Check out the detailed theoretical description on solar cells on PV Education.


How do solar cells work?


Major Milestones in History


Solar is not new. Sun has been over us for million of years and the concept of using sun for energy dates to 1800’s. Several pioneering research in solar cell research have led to the solar cell we see today. Table 1 lists the major events in history which let to the development for solar cells.

Solar Cell Major Discoveries


Solar Cell Types and Efficiency

Maximum Efficiency Reported to date (%)


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