Nanoscience in (Solar) Energy Research Arie Zaban Department of Chemistry Bar-Ilan University Israel Nanoscience in energy conservation: TBP
10 TW - PV Land Area Requirements 10 TW 3 TW
10 TW Power Stations 1400 MW power plant (Hadera) One plant, each day, for the next: 19.5 years
Single-Bandgap Photovoltaics and the solar spectrum (AM 1.5) 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev)
Optimal Bandgap Prince, JAP 26 (1955) 534 Loferski, JAP 27 (1956) 777
Multi-Bandgap Photovoltaics and the solar spectrum (AM 1.5) 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev)
Multi-Bandgap Photovoltaics cost concentration current matching
Maximum Efficiency for an Ideal Multigap System With optical losses Bennett and Olsen, 1988, IEEE PVSC, p. 868
The Photovoltaic (PV) Mechanism
The Green Picture one electron energy contact e - Low energy state Absorber High energy state p + contact Metastable high and low energy state Absorber which transfers charges into the high and low energy states Driving force which brings the charges to the contacts Selective contacts No/slow recombination 1) Green, M.A., Photovoltaic principles. Physica E, 2002. 14: : p. 11-17. 17.
Dye Sensitized Solar Cell (DSSC) TiO 2 Metastable high and low energy state red Absorber to transfer charges into the energy states ox Force driving charges to the contacts glass TCO (Transparent Conducting Oxide) semiconductor dye electrolyte Selective contacts No/slow recombination
Extremely Thin Absorber Cell (ETA) Metastable high and low energy state red Absorber to transfer charges into the energy states ox Force driving charges to the contacts glass TCO (Transparent Conducting Oxide) semiconductor SC electrolyte Selective contacts No/slow recombination
Solid State ETA Cell Metastable high and low energy state Absorber to transfer charges into the energy states Force driving charges to the contacts glass TCO (Transparent Conducting Oxide) semiconductor SC semiconductor Selective contacts No/slow recombination
Electrochemical Absorber Solar Cell Metastable high and low energy state Absorber to transfer charges into the energy states Force driving charges to the contacts glass TCO (Transparent Conducting Oxide) semiconductor electrolyte semiconductor Selective contacts No/slow recombination
Electrochemical Contacts Solar Cell red Metastable high and low energy state ox red Absorber to transfer charges into the energy states ox Force driving charges to the contacts glass TCO (Transparent Conducting Oxide) electrolyte SC electrolyte Selective contacts No/slow recombination
Why Nano? Dye Sensitized Solar Cell TiO 2 Surface area red ox Optical density vs. charge separation efficiency: Injection Exciton diffusion length Charge migration glass TCO (Transparent Conducting Oxide) semiconductor dye electrolyte Materials (quality, cost) Production
High Surface Area Electrode Conductive Substrate Conductive Substrate Conductive Substrate Conductive Substrate Conductive Substrate
TiO2 dye semiconductor Why Nano? Dye Sensitized Solar Cell red ox electrolyte dye ox red glass TCO (Transparent Conducting Oxide) conductive substrate
The Nanoporous Electrode Dye Sensitized Solar Cell Conductive Substrate
Single-Bandgap Photovoltaics and the solar spectrum (AM 1.5) 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev)
Optimal Bandgap Prince, JAP 26 (1955) 534 Loferski, JAP 27 (1956) 777
Multi-Bandgap Photovoltaics and the solar spectrum (AM 1.5) 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev)
Multi-Bandgap Photovoltaics cost concentration current matching
Up-Conversion for a Single Junction 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev) 2 photons of energy 0.5 E g < hν< E g are converted to 1 photon of hν> E g
Down-Conversion for a Single Junction 4E+27 photons/(m 2 ev) 3E+27 2E+27 1E+27 0 0 1 2 3 4 hν (ev) 1 photon of energy hν> 2 E g is converted into 2 photons of hν> E g
Up & Down-Conversion Together 100% Efficiency (AM1.5) Normalized efficiency Ge Cu 2 S GaAs a-si:h a-si:h:f Si CdS I. Lubomirsky, D. Cahen (2005) E g
Nanoscience in (Solar) Energy
END Thank You
Maximum efficiency for an ideal multigap system With optical losses Bennett and Olsen, 1988, IEEE PVSC, p. 868
Basic Cell Characteristics 18 15 12 9 6 i (ma/cm 2 ) -0.8-0.6-0.4-0.2 0 Potential (V) 3 0 9 Voc 769 mv Jsc 16.2 ma/cm 2 Fill Factor 64.3 % Efficiency 8.35 % -0.8-0.6-0.4-0.2 0 Potential (V) 6 3 0 P (µw/cm 2 )
The Nanoporous Electrode wide band-gap semiconductor: TiO 2, SnO 2,Nb 2 O 5, ZnO, SrTiO 3 transparent electrode - visible roughness factor = ~100/µm typical thickness 1-15 µm Conductive Substrate Conductive Substrate µm d=nm
Dye Sensitized Solar Cell (DSSC) dye ox red d=nm µm Conductive Substrate conductive substrate
Dye Sensitized Solar Cell - Fabrication
High Surface Area Electrode Conductive Substrate Conductive Substrate Conductive Substrate Conductive Substrate Conductive Substrate Conductive Substrate Nanoporous Electrode