Surfactant AnalysisAnalysis of the surfactants used in Organic

Solar Cell preparation

Abhishek Upadhyaya Ghimire

Advisor: Dr. Adrienne Stiff-RobertsDepartment of Electrical and Computer Engineering

BackgroundSolar Energy: clean and renewable source of

energyOrganic Solar Cell

AdvantagesLow cost of productionCan be deposited on different surfacesAbility to tailor the molecule properties in

order to fit the applicationDisadvantages

Very low efficiencyShort lifetime

RIR-MAPLE system

RIR-MAPLE systemWater - O-H bond rich, resonates with laser, prevents energy from being absorbed by optoelectronic material

Phenol - secondary solvent - enriches target with hydroxyl bonds and prevents sublimation

Trichlorobenzene - solvent for active materials

Sodium dodecyl sulfate (SDS) - surfactant

RIR-MAPLE emulsion system consists of:

● Emulsion consists of chlorobenzene solution (with PCPDTBT), phenol and DI water (with surfactant) at a ratio of 1:0.25:3 by volume for PCPDTBT

● Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid

Motivation for surfactant analysisIt is expected that the organic solar cells

based on the blended film deposited by RIR-MAPLE should have higher efficiency than the cells fabricated by spin cast.

In reality, the RIR-MAPLE fabricated organic solar cells show poorer performance (3~4 times lower efficiency) than spin-cast solar cells.

One reason to explain the poor performance of RIR-MAPLE fabricated organic solar cells is the presence of insulating surfactant, typically sodium dodecyl sulfate (SDS). Effect of SDS concentration

DTAC

Dodecyltrimethylammonium chloride

Cationic surfactant

● Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)

PEG-PPG-PEG

Surfactant HLB value in water-oil system

SDS 40

PEG-PPG-PEG, Pluronic F-68 >24

DTAC 20

Surfactant 0.001 wt% DTAC

0.01 wt% DTAC 0.1 wt% DTAC 0.5 wt% DTAC 1 wt% DTAC

Volume of PCPDTBT solution

1.755 ml 0.91 ml 0.92 ml 1.17 ml 1.12 ml

Volume of surfactant

5.256 ml 2.73 ml 2.76 ml 3.51 ml 3.36 ml

Experimental dataSurfactant 0.001 wt% PEG-

PPG-PEG0.01 wt% PEG-

PPG-PEG0.1 wt% PEG-

PPG-PEG0.5 wt% PEG-

PPG-PEG1 wt% PEG-PPG-PEG

Volume of PCPDTBT solution

1.25 ml 1.12 ml 0.92 ml 0.97 ml 0.95 ml

Volume of surfactant

3.75 ml 3.36 ml 2.76 ml 2.91 ml 2.85 ml

0.5 wt% of PEG-PPG-PEG and DTAC

1 wt% of PEG-PPG-PEG and DTAC

Mixed SurfactantsSurfactant mixture Ratio and Concentration

DTAC with SDS 0.01 wt% DTAC + 0.0001 wt% SDS

PEG-PPG-PEG with SDS 0.01 wt% PEG-PPG-PEG + 0.0001 wt% SDS

0.001 wt% PEG-PPG-PEG + 0.0001 wt% SDS

● The motivation behind mixing the surfactants was to see the effect of mixed surfactants in the preparation of stable emulsion.

● Could not prepare a stable emulsion using the mixed surfactants

MAPLE growth using DTAC and PEG-PPG-PEG1 wt% DTAC and 0.5 wt % PEG-PPG-PEG5 mg PCPDTBT in 1 ml of TCB and 3 ml of deionized water containing

surfactant

DTAC PEG-PPG-PEG

XRD results

AFM results: DTAC

AFM results: PEG-PPG-PEG

Conclusion and Future worksEmulsions prepared using DTAC and PEG-PPG-PEG with

concentration lower than 0.5 wt% are not stable0.5 wt% is very high concentration for surfactant to be used in MAPLE

growth, and this would not help on the purpose of increasing the efficiency of organic solar cell

Adding phenol with DTAC or PEG-PPG-PEG made the emulsion even more unstable

Perform Photo-CELIV or other efficiency test for the solar cell grown using DTAC and PEG-PPG-PEG

Perform similar analysis for other surfactants such as Polyoxyethylene tridecyl ether (PTE) and Cetyltrimethylammonium bromide (CTAB).

Referenceshttps://soar-ir.shinshu-u.ac.jp/dspace/bitstream/10091/162/1/aqueous_surfactant_solutions.pdf

(DTAC HLB)Required HLB values http://www.firp.ula.ve/archivos/historicos/76_Book_HLB_ICI.pdfPEG-PPG-PEG HLB values

http://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=22686648

http://www.brighthub.com/environment/renewable-energy/articles/95572.aspxHLB value of CTAB

http://journals.tubitak.gov.tr/chem/issues/kim-05-29-1/kim-29-1-4-0401-15.pdfhttp://pubs.rsc.org/en/content/articlepdf/2010/jm/c0jm02091ehttp://www.sigmaaldrich.com/materials-science/material-science-products.html?TablePage=22686648