Quantum DotsAn innovative technology for highly

efficient solar cells

Seminar presented byAmit Coudhary

Asst. Prof.ECE Deptt.

AKGEC Ghaziabad

Introduction to Solar Cells Basic problems with solar cells Multi Layer Solar cell Cost of solar power Semiconductor Quantum Dots Quantum Dots Solar cells Synthesis of Cd-Se Quantum Dots Other applications of Quantum Dots Conclusion

Contents

A solar cell basically is a semiconductor PN junction diode.

Sun light Photons, which have energies comparable to band gap of semiconductor are absorbed by valance band electron and they produce e--h+ pair.

This leads to flow of current in external circuit

Introduction to Solar Cells

Dominant solar cell technology use silicon. Band gap of Si is 1.1eV. If we see Solar Spectrum

Thus Solar to electrical energy conversion efficiency is about 30%

Basic problems with solar cells

Three layer (InGaAs/ GaAs/ InGaP) solar cells, in which three layer have three different Band gaps (1.89/1.42/0.94 eV), can absorb photons from wider range of solar spectrum

Hence their efficiency is higher (48%) as compared to Si solar cells

An infinite layer solar cell will has theoretically maximum efficiency of 86%

Multi Layer Solar cell

Low efficiency of solar cells and their high cost make per unit cost of solar power very high

Cost of solar power

Quantum Dots are semiconductor particles having nanometer dimensions. A QD can have 100 to 100000 atoms

Solution of Schrodinger wave equation for QD suggest that their Band Gap is inversely proportional to their diameter

Examples of QDs are Cd-Se, Zn-O, In-P etc

Semiconductor Quantum Dots

Quantum Dots Solar cells

CdO is added with oleic acid and Octadecene. Then this mixture is heated up to 225o C.

  Selenium solution is added to this solution. It produce seed

Cd-Se crystals which grows in size with time

Different samples are taken after each 3 minutes . Thus each sample has Cd-Se QDs with different sizes

Synthesis of Cd-Se Quantum Dots

Other applications of Quantum Dots

By using QDs, efficiency of solar cells can be increased up to 86% (Theoretically maximum efficiency)

This will reduce the per unit cost of solar power

Will also help to make our environment pollution less

Conclusion

Thank You