1. 「 Quantum dot solar cells 」 A. J. Nozik, Physica E 14 (2002) 115-120. YOSHIDA Lab. Hiroaki KAMIOKA

2. contents Introduction Necessity of Quantum dot solar cells Ways to increase conversion efficiency Proposals of Quantum dot solar cell configuration Summary

3. Present source of energy supply Present source of energy supply Environmental pollution Eco-friendly new energy Solar energy generation BAD!! Introduction Necessity of Quantum dot solar cells

4. Conversion efficiency of current solar cells Conversion efficiency of current solar cells About ２０ ％ currently About ３１ ％ Theoretical limit Technical progress Current solar cells can't cover the demand of energy on earth Current solar cells can't cover the demand of energy on earth

5. Quantum dot solar cells Quantum dot solar cells Necessity for new technological idea!!

6. Quantum Dot (it is a semiconductor whose excitons are confined in all three spatial dimensions)‏ bulkQuantum dot Discretization of energy level Discretization of energy level

7. Present source of energy supply Present source of energy supply Environmental pollution Eco-friendly new energy Solar energy generation BAD!! Introduction Necessity of Quantum dot solar cells

8. Conversion efficiency of current solar cells Conversion efficiency of current solar cells About ２０ ％ currently About ３１ ％ Theoretical limit Technical progress Current solar cells can't cover the demand of energy on earth Current solar cells can't cover the demand of energy on earth

9. Quantum dot solar cells Quantum dot solar cells Necessity for new technological idea!!

10. Quantum Dot (it is a semiconductor whose excitons are confined in all three spatial dimensions)‏ bulkQuantum dot Discretization of energy level Discretization of energy level

11. W ＝ × Higher photovoltages :V or Higher photocurrents :I Way to increase conversion efficiency V I W:watt V :voltage I :current

12. Quantum dot Function of quantum dot for the solar cells Higher photovoltages from “discretization” e h e h V２V２ V 1 ＜ V ２ Higher photovoltages V1V1 Bulk E c: bottom of conducton band E v: top of valence band

13. Function of quantum dot for the solar cells Higher photocurrents from “Impact ionization” Higher photocurrents

14. Function of quantum dot for the solar cells Higher photovoltages from “ Separation” normal Separation!! Higher photocurrents balkQuantum dot

15. Quantum dot arrays in p-i-n cells intrinsicP-typeN-type

16. Quantum dot-sensitized nanocrystalline TiO2 solar cells

17. Quantum dots dispersed in organic semiconductor polymer matrices

18. Summary If quantum dot cells get achieved, conversion efficiency can increase incredibly. It is important to get hot electrons without loss or to get many electrons by impact ionization. It is the most important that this theory is just an expectation.