1. Presented to: Presented by:
S. K. Chaudhary Educational Trust’s Shankara Institute of Technology Kukas, Jaipur (Rajasthan)
PRESENTATION ON
INTERMEDIATE BAND QUANTUM DOT SOLAR CELL
Presented to:
Mr. Rajesh Kanwadia
Ms. Shweta Agarwal
(Sr. Lecturer, Seminar Incharge)
Presented by:
VINEET KUMAR
Electronics & communication Engg.
B.Tech IV Year(VIIIth Sem)

2. CONTENTS Photovoltaic Conventional solar cell Introduction Working
Limitations
Energy bands in solids
Intermediate band solar cell
Quantum dot
Intermediate band quantum dot solar cell
Construction
Advantages
Applications

3. Introduction to Photovoltaic
Generations of voltage from photons
Light energy ( photons) are converted into electrical energy
( voltage).
This conversion is called
“ photovoltaic effect”.

4. Photovoltaic Generations
First generation: silicon wafer-based solar cells
Second generation: thin-film deposits of semiconductors
Third generation: photo-electrochemical cells

5. Solar Cell
The solar cell (or photovoltaic cell) is a device that converts light energy into electrical energy.
Fundamentally, the device needs to fulfill only two functions:
1. Photo-generation of charge carriers (electrons and holes) in a light-absorbing material.
2. Separation of the charge carriers to a conductive contact that will transmit the electricity.

6. Intermediate band solar cell
The intermediate band (IB) is an electronic band located within the semiconductor band gap, separated from the conduction and the valence band by a null density of states.
Intermediate band solar cells (IBSCs) are photovoltaic devices.
Used to exploit the energy of below band gap energy photons.

7. ASSUMPTIONS Only radiation recombination
One electron-hole pair per photon
Constant quasi-Fermi levels
No high energy photons in low energy processes
Maximum concentration of solar radiation

8. Intermediate band Requirements
Higher photocurrent
Higher efficiency arising from absorption of 2 sub-band gap photons to create one electron-hole pair.
High voltage
V=(EFCB - EFVB)/q
V~Eg for main semiconductor
Essential for operation
3 quasi-Fermi levels
IB “disconnected” from emitters
Need IB half-filled with electrons
Non-overlapping absorption coefficients

9. How can we introduce these intermediate energy levels in the band gap?
Answer
“Introduce Quantum Dots”

10. Quantum Dot
A quantum dot is a portion of matter (e.g., semiconductor) whose excitons are confined in all three spatial dimensions.
Quantum dots have properties combined between
Those of bulk semiconductors
Those of atoms

11. Physical structure
The structure is as follow :

12. Quantum Dot : Types

13. Operational principles of IBSC
Incoming photons to base layer can cause three different transitions between valance band (VB), conduction band (CB) and IB depending on their energy:
VB→CB, if the photon energy is greater then ECV.
VB→IB, if the photon energy is greater then EVI
IB→CB, if the photon energy is greater then ECI.

14. Salient characteristics of QDs for IBSC
Dot sized shape, composition
Dot spacing
Dot regularity
Materials
Doping

15. ADVANTAGES Higher Efficiency. Balance between the two factors (I) Cost
(II) Efficiency

16. APPLICATIONS Photovoltaic devices: solar cells
Light emitting diodes: LEDs
Quantum computation
Flat-panel displays
Memory elements
Photodetectors
Lasers

17. What limits performance of these QD IBSC?
Low open-circuit voltage
Low currents
Cost

18. Conclusions
QD SL cells show photo responses extended to longer wavelengths than GaAs control cells, demonstrating current generation from the absorption of sub-band gap photons.
IBSC theoretically offers a way to significantly increase cell efficiency compared to that of a single-junction solar cell.

20. Queries