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Computational Materials Design for highly efficient CIGS solar sells

Computational Materials Design for highly efficient CIGS solar sells. Presenter Tani Yoshimasa. CONTENTS. 1. INTRODUCTION 2. MY THEME 3. DISCUSSION 4. SUMMARY . INTRODUCTION. First-principles calculation. Comparison with the experiment. Use only atomic

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Computational Materials Design for highly efficient CIGS solar sells

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  1. Computational Materials Design for highly efficient CIGS solar sells Presenter Tani Yoshimasa

  2. CONTENTS 1. INTRODUCTION 2. MY THEME 3. DISCUSSION 4. SUMMARY

  3. INTRODUCTION First-principles calculation Comparison with the experiment • Use only atomic • number and crystal • structure. • Calculate electronic • structure. Experiment Theory H.Kasai H.Akai H. Katayama-yoshida Introduction to Computational Matr , 16 ,1992

  4. INTRODUCTION Computational Maerials Design New matrials CuIn1-xGaxSe2 Get properties ! Calculate by computer

  5. INTRODUCTION Advantage of CMD • Simulation without sample materials • Lower cost than experiment • No risk with treating dangerous materials

  6. INTRODUCTION The present of solar cells Si solar cells Nowadays , CIGS solar cells attract attention ～30 yen / kWh It can be less than electrisity cost used in our home. CIGS solar cells Solar cells are mainly made by Si single crystals. However, the cost is very high. 47～63 yen / kWh

  7. MY THEME Property of CuInSe2 • Nature of structual defect • Large light absorption coefficient • CuIn1-xGaxSe2 are high efficiency than CuInSe2 Low cost ! 100 times of Si ! Crystal structure of CuInSe2 Cu In Se Why ?

  8. MY THEME Electronic structure of CuInSe2 Energy Bands Density of States Band gap 0.71 eV Exp. Cu-3d and Se-4p Exp. data 1.04 eV Exp. Se-4s S.Kohigi M.Nishitanietc. PRB 45 , 16 ,1992 TΓN

  9. MY THEME Question • Why CuIn1-xGaxSe2 are high efficiency than CuInSe2 or CuGaSe2 ? • The system has a tendency toward spinodal decomposition !

  10. DISCUSSION Spinodal decomposition Zn1-xCrxTe The system favors the phase separation. High and low concentration region of impulity in the materials. T. FUKUSHIMA et al. Japanese Journal of Applied Physics Vol. 45, No. 15, 2006

  11. DISCUSSION Mixing energy of CuIn1-xGaxSe2 ΔE = E (CuIn1-xGaxSe2) – [ (1 – x) E(CuInSe2) + x E(CuGaSe2) ] Mixed state Not mixed state Mixing energy ΔE Positive mixing energy In and Ga are seperated !

  12. DISCUSSION How to exchange sunlight to electricity E before after n-type p-type CBM recombine VBM electron hole excited electron

  13. DISCUSSION Heigh efficient CIGS solar cells Band alignment Image of solar cells recombine

  14. SUMMARY SUMMARY • Due to positive mixing energy of CuIn1-xGaxSe2 , we can expect spinodal decomposition. • Efficient electron-hole separation is expected leading to highly efficient photovoltaic effect.

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