Course schedule. Universität Karlsruhe (TH)

Transcription

1 Course schedule 1 Preliminary schedule 1. Introduction, The Sun 2. Semiconductor fundamentals 3. Solar cell working principles / pn-junction solar cell 4. Silicon solar cells 5. Copper-Indiumdiselenide solar cells 6. Cell optimization and highly efficient device concepts 7. Modules and system integration 8. Organic photovoltaics 9. Dye sensitized solar cells 10. Economics and profitability 11. Other renewable energies 12. Excursion

2 Dye sensitized solar cells 2

3 Background : Dr. Michael Grätzel created the Grätzel Cell (dye sensitized solar cell DSSC) at EPFL Promising technology: low cost easy manufacturing power conversion efficiency of 10% Companies: Dyesol (Queanbeyan, Australia) G24i (Wentloog, Cardiff) Dr. Michael Grätzel

4 Companies 4 Dyesol: selling materials (dyes, electrolytes, ) and equipment (screen printer, dye applicator, electrolyte filling machine, ) G24i: licensed EPFL technology

5 Schematic structure 5

6 Schematic structure 6

7 TiO 2 photoelectrode 7 TiO 2 collodial solution (or paste) sintered at C Film thickness typ. 10 µm Roughness factor > 1000 gives large actual surface Porosity of 50-70% needed for sufficient electrolyte film penetration TiO 2 film SEM photograph

8 Ru complex photosensitizer 8 Typical Ru complex sensitziers developed by Grätzel s group

9 Ru complex photosensitizer 9

10 Ru complex photosensitizer 10 Ru complexes with carboxyl groups to anchor the TiO 2 surface Coverage of the TiO 2 surface with N3 dye near 100% N3 dye adsorbed on the (101) surface of TiO 2

11 Redox electrolyte 11 e - I - I 3 - e - TiO 2 e - Dye Redox Electrolyte Cathode Electrolyte contains I - /I 3 - redox ions for electron mediation between the TiO 2 photoelectrode and the counter electrode Cell performance depends on: - counter cations of iodides (e.g. Li +, Na +, K + ) - viscosity of solvents

12 Counter electrode 12 e - I - I 3 - e - TiO 2 e - Dye Redox Electrolyte Cathode I 3 - ions are re-reduced to I - ions at the counter electrode Pt coated on TCO (approx. 200 nm) or carbon are typically used

13 Sealing materials 13 Prevent leakage of the electrolyte and the evaporation of the solvent Chemical and photochemical stability against the electrolyte component, iodine and the solvent is required

14 Primary processes 14

15 Photovoltaic performance 15

16 Photovoltaic performance 16

17 Charge-transfer kinetics 17

18 Dark current Recombination of injected electrons with I 3 - ions: 18 I3 + 2e ( TiO2) 3I

19 Electron transport in TiO 2 film 19 Very small electron conductivity in TiO 2 film Conductivity in DSSC significantly increased due to electron injection from the photosensitizers under photon irradiation Conductivity and photocurrent response increase with increasing light intensity

20 Characteristics 20 High energy conversion efficiency Low-cost fabrication Abundant supply of component materials Good potential for colorful, adaptable consumer products Low potential for environmental pollution Good recycability

21 DSSC Fabrication 21 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

22 DSSC Fabrication 22 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

23 DSSC Fabrication 23 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

24 DSSC Fabrication 24 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

25 DSSC Fabrication 25 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

26 DSSC Fabrication 26 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell Sputtering process

27 DSSC Fabrication 27 Preparation of TiO 2 colloid Preparation of the TiO 2 electrode a) Doctor blading b) Screen printing Dye fixation onto the TiO 2 film Redox electrolyte Counter electrode Assembling the cell

28 Cell Performance 28

29 New oxide semiconductor film photoelectrodes 29 Replace TiO 2 by: ZnO η = 2.5% SnO 2 η = 0.65% Nb 2 O 5 η =2.6% In 2 O 3 η = 0.38% SrTiO 3 η =1.8% Combine two oxide semiconducter materials Tennakone et al. SnO 2 /ZnO η =8%

30 New dye photosensitizers 30

31 Organic and natural dye photosensitizers 31 variety of structures for molecular design cheaper than metal complexes large absorption coefficients

32 New electrolyte 32 Replace volatile organic solvents by room-temperature ionic liquids (molten salts) high ion conductivity electrochemical stabitiy nonvolatility

33 Solid state DSSCs 33 1, conducting F-doped SnO 2 -coated glass 2, compact TiO 2 layer 3, dye-sensitized heterojunction 4, gold electrode

34 Quasi solid state DSSCs 34 Gelator used to replace liquid electrolyte Gelator added to the electrolyte at elevated temperature Hot electrolyte solution appicated on dye-coated TiO 2 layer

35 Prospects 35 Improvement of efficiency Long-term stability for outdoor applications Solid electrolyte

36 Prospects 36