SLIDE 1
Organic Solar Cells
e- LUMO ITO Al hv e- LUMO ITO ITO Al h+ HOMO Al
Bulk heterojunction structure
Donor Acceptor
Bulk heterojunction structure
Hiramoto et al., Appl. Phys. Let., 1991, 58, 1062. Yu et al., Science 1995, 270, 1789.
Nanomorphology controls in colloidal nanocrystal polymer bulk - - PowerPoint PPT Presentation
Nanomorphology controls in colloidal nanocrystal polymer bulk - - PowerPoint PPT Presentation
Nanomorphology controls in colloidal nanocrystal polymer bulk heterojunction solar nanocrystal polymer bulk heterojunction solar cells based on non-toxic inorganic acceptors and functional block copolymers functional block copolymers
SLIDE 2
SLIDE 3
Hybrid Solar Cells
・ Weak Absorption in Visible ・ Weak Absorption in Visible ・ Poor Electron Mobility
PCBM
Hybrid Solar Cells Hybrid Solar Cells Inorganic Materials as Electron Acceptors
e-
Advantages ・Absorption of visible light
ITO Al e-
LUMO CB
hn
・Absorption of visible light ・High electron mobility
ITO Al h+
HOMO VB
Donor (Organic) Acceptor (Inorganic) h+
SLIDE 4
Hybrid Solar Cells
CdSe tetrapod CdSe tetrapod
30~50 nm 5 nm
PCPDTBT (Low bandgap polymer)
50 nm
PCE : 3.13 % Absorption of CdSe PCE : 3.13 % Highest PCE in polymer/nano particle hybrid solar cells
Dayal, et al., Nano Letters 2010 10 (1), 239-242
SLIDE 5
Bismuth Sulfide (Bi2S3)
10 nm
・Non-toxic (Cd, Pb have toxicity)
10 nm
・Non-toxic (Cd, Pb have toxicity) ・Band gap: 1.3 eV (CB: -4.3 eV, VB:-5.6 eV)
- Strong absorption in near IR region
→ Contribution to light harvesting → Contribution to light harvesting
Good n-type Material Good n-type Material for Environmental Friendly Hybrid Solar Cells Hybrid Solar Cells
SLIDE 6
Polymer : Bi2S3 device (Bilayer) (From ICFO group)
Voc = 0.32 V Jsc = 3 mAcm−2 FF = 49% FF = 49% PCE = 0.46%
Martinez, L.; Konstantatos, G., Adv. Ener. Mater., 2011, 1, 1029.
Bulk heterojunction device
Martinez, L.; Konstantatos, G., Adv. Ener. Mater., 2011, 1, 1029.
SLIDE 7
Problem of Bulk Heterojunction Device
Ag
Device structure Cross sectional SEM image of BHJ device
Ag MoO3 Top P3HT layer
Cross sectional SEM image of BHJ device Bi2S3 NPs P3HT
Blend of P3HT and Bi2S3 Bi2S3 layer (Hole blocking layer)
P3HT
(Hole blocking layer) ITO
Very Poor Mixing between Bi2S3 NPs and P3HT Very Poor Mixing between Bi2S3 NPs and P3HT Small D/A interface area limits its efficiency Need to control morphology in BHJ device → PCE : ~0.7% Small D/A interface area limits its efficiency Need to control morphology in BHJ device By interactions between functional polymers and NPs
SLIDE 8
Thiol Containing Block Copolymer
S n block S m
SH-P3HT
Thiol groups
h+
SH
Expectation
NPs
h
P3HT Functional P3HT Interactions in Solution
e-
Self-assembled Small D/A Domains Small D/A Domains
O N S S S n l m
This Idea Stems from Our Previous Work
O O N N N
This Idea Stems from Our Previous Work Fullerene attached block copolymer
Miyanishi et al. Macromolecules, 2012, 45, 6424
SLIDE 9
Discussions
By attaching NPs through thiol group,
SH-P3HT domain has poor crystallinity
By attaching NPs through thiol group, packing of P3HT might be disturbed
SH-P3HT domain has poor crystallinity Reasons of VOC increase and JSC decrease ・Worse packing of polymer ・Worse packing of polymer ・Isolation of NPs
LUMO
Lower HOMO Bad charge transport pathway
HOMO LUMO
VOC increase h+
VOC ↑ JSC ↓
Lower HOMO Worse packed P3HT
Amount of thiol groups seem too much Use blend of normal P3HT and SH-P3HT or less thiol containing SH-P3HT
SLIDE 10
Summary
- Thiol Functionality Significantly Improved Morophology in
- Thiol Functionality Significantly Improved Morophology in
NPs/Polymer Blend Films.
- Controlling Degree of Aggregation by Mixing P3HT and SH-P3HT
Enhanced PCE to Close to 1 %.
S n block S m
h+
n m SH
SH-P3HT
e-