Supporting Information: Polymer Light-Emitting Electrochemical Cell ...
Supporting Information:
Polymer Light-Emitting Electrochemical Cell Blends Based on Selection of Lithium Salts, LiX [X = Trifluoromethanesulfonate, Hexafluorophosphate, and Bis(trifluoromethylsulfonyl)imide] with Low Turn-On Voltage
Kenji Jianzhi Chee†,‡, Vipin Kumar†, Cuong Viet Nguyen †, Jiangxin Wang† and Pooi See Lee†,‡*
†
‡
School of Materials Science and Engineering, 50 Nanyang Avenue, Nanyang Technological University, Singapore-639798
Institute for Sports Research, 50 Nanyang Avenue, Nanyang Technological University, Singapore-639798
*Corresponding Author: [email protected]; Tel (+65) 6790-6661
S1
Supporting Information
Figure S1. Nyquist plot of LiTFSI, LiCF3SO3 and LiPF6 based MEH-PPV LEEC films (PEO/Li+ ~ 30) for the determination of ionic conductivity with enlarged axis in the inset.
S2
(a)
(b)
(c)
Figure S2. (a) TFSI- anion shows a total of 5 resonance states, (b) CF3SO3- anion shows a total of 4 resonance states and (c) PF6- anion does not show any resonance state.
S3
Figure S3. Cyclic voltammetry data recorded using a working electrode of thermally evaporated Au coated with a thin film of MEH-PPV. The electrolyte solution was 0.1 M LiX (X = CF3SO3- & TFSI-) + 2 M PEO (Mn = 400) in CH3CN. A silver wire was used as the quasi-reference electrode, and it was calibrated vs the Fc/Fc+ reference redox couple at the end of each measurement. The counter electrode was Pt plate. The scans were done with rates of 25 mV/s in an Ar environment with accordance to L. Edman et. al. 1. The TFSI based LEEC device shows earlier onset of doping due to the peak potential blue-shifts compared to CF3SO3 based LEEC. This correlates to the lower activation energy required for doping to occur in MEH-PPV. In the negative potential range, it is apparent that the TFSI based LEEC shows a reversible n-type doping of MEH-PPV before the onset of an irreversible reduction reaction. However, in the case of CF3SO3, the stability is lower as there is an observable irreversible reduction before the n-type doping of MEH-PPV. Thus, the TFSI based LEEC device would be more electrochemically stable.
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Figure S4. CIE 1931 plot of LEEC with device area of 15mm2 based on different lithium salts in the PEO-Li+ electrolyte.
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REFERENCES (1) Fang, J.; Matyba, P.; Robinson, N. D.; Edman, L., Identifying and Alleviating Electrochemical Side-Reactions in Light-Emitting Electrochemical Cells. J. Am. Chem. Soc. 2008, 130, 4562-4568.
S6
Polymer Light-Emitting Electrochemical Cell Blends Based on Selection of Lithium Salts, LiX [X = Trifluoromethanesulfonate, Hexafluorophosphate, and Bis(trifluoromethylsulfonyl)imide] with Low Turn-On Voltage
Kenji Jianzhi Chee†,‡, Vipin Kumar†, Cuong Viet Nguyen †, Jiangxin Wang† and Pooi See Lee†,‡*
†
‡
School of Materials Science and Engineering, 50 Nanyang Avenue, Nanyang Technological University, Singapore-639798
Institute for Sports Research, 50 Nanyang Avenue, Nanyang Technological University, Singapore-639798
*Corresponding Author: [email protected]; Tel (+65) 6790-6661
S1
Supporting Information
Figure S1. Nyquist plot of LiTFSI, LiCF3SO3 and LiPF6 based MEH-PPV LEEC films (PEO/Li+ ~ 30) for the determination of ionic conductivity with enlarged axis in the inset.
S2
(a)
(b)
(c)
Figure S2. (a) TFSI- anion shows a total of 5 resonance states, (b) CF3SO3- anion shows a total of 4 resonance states and (c) PF6- anion does not show any resonance state.
S3
Figure S3. Cyclic voltammetry data recorded using a working electrode of thermally evaporated Au coated with a thin film of MEH-PPV. The electrolyte solution was 0.1 M LiX (X = CF3SO3- & TFSI-) + 2 M PEO (Mn = 400) in CH3CN. A silver wire was used as the quasi-reference electrode, and it was calibrated vs the Fc/Fc+ reference redox couple at the end of each measurement. The counter electrode was Pt plate. The scans were done with rates of 25 mV/s in an Ar environment with accordance to L. Edman et. al. 1. The TFSI based LEEC device shows earlier onset of doping due to the peak potential blue-shifts compared to CF3SO3 based LEEC. This correlates to the lower activation energy required for doping to occur in MEH-PPV. In the negative potential range, it is apparent that the TFSI based LEEC shows a reversible n-type doping of MEH-PPV before the onset of an irreversible reduction reaction. However, in the case of CF3SO3, the stability is lower as there is an observable irreversible reduction before the n-type doping of MEH-PPV. Thus, the TFSI based LEEC device would be more electrochemically stable.
S4
Figure S4. CIE 1931 plot of LEEC with device area of 15mm2 based on different lithium salts in the PEO-Li+ electrolyte.
S5
REFERENCES (1) Fang, J.; Matyba, P.; Robinson, N. D.; Edman, L., Identifying and Alleviating Electrochemical Side-Reactions in Light-Emitting Electrochemical Cells. J. Am. Chem. Soc. 2008, 130, 4562-4568.
S6
