Acceptor-Donor-Acceptor small molecules based on derivatives of 3,4-ethylenedioxythiophene for solution processed organic solar cells Boniface Y. Antwi (AMRSC) PhD Chemistry Candidate (Year 4) University of Ghana, Legon –Accra. Supervisors Prof. Robert Kingsford-Adaboh Prof. Peter J. Skabara (FRSC) Dr. Richard Boakye Owoare
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Acceptor–donor–acceptor small molecules based on derivatives of 3,4-ethylenedioxythiophene for solution processed organic solar cells
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Acceptor-Donor-Acceptor small molecules based on derivatives of 3,4-ethylenedioxythiophene for solution
processed organic solar cells
Boniface Y. Antwi (AMRSC)PhD Chemistry Candidate (Year 4)
University of Ghana, Legon –Accra.
Supervisors
Prof. Robert Kingsford-Adaboh
Prof. Peter J. Skabara (FRSC)
Dr. Richard Boakye Owoare
Overview
Introduction
Background
Objectives
Synthesis of small molecules
Physical properties (DSC, TGA, UV-vis, CV)
Device fabrication and testing
Morphological Study
Conclusion
An hour sunshine is enough to power the world for twenty years.
1.33 octillion (1027 ) Btu solar energy per hour reaches theearth.1
0.82 quintillion (1018 ) Btu global energy demand by 2040.2
Organic solar cells (OSC) have unique properties.3
flexible
easy to process
light weight
wide area applicability
1. A. Mishra and P. Bauerle , Angew. Chem. Int. Ed. 2012, 51, 2020 – 2067.2. http://www.eia.gov/todayinenergy/detail.cfm?id=12251; 13.06.2016; 12:08 GMT3. R. Po and J. Roncali, J. Mater. Chem. C, 2016, 4, 3677–3685.
Best HOMO-LUMO energy gap-(1.57 eV, DIN-2TE thin film)
Figure 3. Normalised absorption spectra of DIN-2TE, DRH-2TE, and DECA-2TE (a) in solution and (b) drop cast film.
Electrochemical properties
Figure 4 Cyclic voltammograms of DIN-2TE, DRH-2TE,and DECA-2TE in dichloromethane solution (10-4 M)with Bu4NPF6 supporting electrolyte (0.1 M), recordedat a scan rate of 100 mV s-1.
-2 0 2
DECA-2TE
DRH-2TE
DIN-2TE
Cu
rre
nt
Potential / V vs Fc/Fc+
Fc/ Fc+
DIN-2TE DRH-2TE DECA-2TE
Potential (V)
Reversible (E1/2)
+0.33, and +0.72.
+0.66, +1.15 and -1.50
Irreversible +0.69, +1.16,and -1.62
+1.14, and -1.64.
HOMO (eV) -5.49 -5.13 -5.46
LUMO (eV) -3.18 -3.16 -3.30
Eg (eV) 2.31 1.97 2.16
Table 2. Electrochemical properties of DIN-2TE, DRH-2TE andDECA-2TE small molecules.
Device Fabrication
𝑷𝑪𝑬 =𝑱𝒔𝒄 × 𝑭𝑭 × 𝑽𝒐𝒄
𝑷𝒊𝒏
Device performance
DEVICEJsc
(mA cm-2)
Voc
(V)FF
PCE
(%)
DRH-2TE: PC71BM
(1:3) a3.04 0.64 0.30 0.63
DRH-2TE: PC71BM
(1:3) a c5.60 0.68 0.35 1.36
DECA-2TE: PC71BM
(1:4) b2.96 0.85 0.41 1.03
DECA-2TE: PC71BM
(1:4) b c2.99 0.90 0.39 1.05
-0.3 0.0 0.3 0.6 0.9
-8
-4
0
4
8
Cu
rre
nt
de
nsity/
mA
cm
-2
Voltage / V
DRH-2TE:PC71
BM_without DIO
DRH-2TE:PC71
BM_with 1% DIO
(a)
-0.4 0.0 0.4 0.8
-3
-2
-1
0
Cu
rre
nt
de
nsity /
mA
cm
-2
Voltage / V
DECA-2TE:PC71
BM_without DIO
DECA-2TE:PC71
BM_with 1% DIO
(b)
a60 °C and b90 °C annealing temperatures for 20 mins, c1 %
diiodooctane.
Table 3. Summary of the average optimisedphotovoltaic performance for DRH-2TE and DECA-2TE devices. AM 1.5G illumination.
Figure 5. Current–voltage curves of optimised (a) DRH-2TE and (b) DECA-2TE bulk-heterojunction devices without and with 1% DIO additive under AM 1.5 G illumination.
Figure 5: Tapping mode AFM height images of best performing DECA-2TE device without DIO (left) and with 1% DIO(right). 1:4 D/A weight ratio, annealed at 60°C.
Figure 6: Tapping mode AFM height images of best performing DRH-2TE device without DIO (left) and with 1% DIO(right). 1:3 D/A weight ratio, annealed at 90°C.
Three novel low bandgap A-D-A small molecules have been synthesised.
Power conversion efficiencies, 1.36% and 1.05% have been recorded for DRH-2TE and DECA-2TE based BHJ organic solar cells respectively.
DIN-2TE was unsuitable for solution processable BHJ OSC application, due to its poor solubility.