Solar PV Cells

  • Solar PV is the mainstay of solar energy particularly with decreasing cost of PV cells in the recent times.
  • Photo voltaic cell is an example of photodetector devices which work on the basis of photoelectric effect.
  • It is a way of directly using sunlight to produce electricity.

Photoelectric Effect

  • Photoelectric effect, 1st demonstrated by Einstein, relies on the interaction of photons and electrons and their behaviour during interaction.
  • Flash a beam of light on to some material like metal it will knock-off electrons, collect these electrons at an electrode. Connect the electrode to a wire and there you have electricity.

Working of PV Cells

image 38
  • A photovoltaic panel creates electricity when a photon hits the silicon surface and pushes an electron out of the top layer of the silicon and across an electrical junction inside the panel.
  • The movement of this electron creates a useful voltage. When wires are connected to produce a circuit, this voltage means that current will flow, eventually taking the displaced electron back to the top layer.
  • Solar cells work best in strong sunlight but will also generate some power on an overcast day from the diffused light that gets through the clouds. 
  • Nature of electrical energy from PV cells
  • DC current

Types of PV Cells

  1. 1st gen: Single crystal PV cells
  2. 2nd Gen: Thin-film PV cells
  3. 3rd Gen: Perovskites

1st  Generation PV cells

  • These are basically silicon-based.
  • Single crystal silicon: have the highest efficiency, around 20-25%, high-cost manufacturing
  • Amorphous silicon (powdered): efficiency is 5%, used in calculators

2nd Generation PV cells: Polycrystalline PV cells

Cadmium Telluride:

  • CdTe can be deposited on thin sheets. So you can make flexible PV panels.
  • CdTe absorbs sunlight readily to release electrons. So thin sheets can be made.
  • Efficiency ~ 15%
  • Disadvantage is cadmium is highly toxic.
  • Tellurium is not available as it is a rare earth metal. It is found in under-water ridges. 

CIGS: Copper Indium Gallium Selenide


  • Similar to CdTe, it can absorb sunlight readily. Besides it is not toxic like CdTe.
  • Disadvantage: Indium is in short supply 
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Multi-Junction PVs: Gallium-Arsenic, Indium, Germanium

  • Layers of semiconductor and metal
  • Main advantage is high efficiency because different materials absorb different wavelengths from the sun. 

3rd Generation PV cells


  • The main advantage of perovskites is they can used to make PV paints which can be painted on conformal surfaces like cars.
  • Very recently organic-perovskite solar cells have reached efficiency of a record-breaking 24%
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