Measuring the UV-VIS for a polymer in thin film would be a good tool.

mobility measurements with voltametry analysis (HOMO-LUMO )could be two complementary technics to well determine your compounds

A polymer acts as donor or acceptor always in comparison to other compound. In that sense, being acceptor or donor is not an inherent property of a polymer. For instance, PCBM would act as acceptor in a blend made of P3HT (LUMO~2.7eV HOMO~4.9eV) with PCBM (LUMO~3.9eV HOMO~5.9eV). But the same PCBM would act as donor in a hypothetical blend made of ZnO (LUMO~4.4eV HOMO~7.6eV) with PCBM (LUMO~3.9eV HOMO~5.9eV).

Consequently, to determine the donor or acceptor behavior of a polymer in a blend you will need to determine the LUMO-HOMO levels which is commonly achieved using cyclic voltammetry. Additionally you could use visible spectroscopy to determine the bandgap.

In order to find whether the synthesized CP is acceptor or donor, do Mott-Schottky analysis, this gives you the densities of acceptor and donor materials. In supporting, quenching process in PL instruments (i.e) first run PL for ur donor material, then by addtion of some acceptor material into donor material, the PL peak suppresses which also implies the quenching process.

If the chain contains donor and acceptor units then it will show solvatochromism in fluorescence. Measure the emission spectra in a range of solvents having different polarities and you will observe well structured excitonic or LE emission in non polar solvents. As the solvent polarity increase the emission will shift to the red, loose structure to become a gaussian band. This is the charge transfer emission , CT, from the stabilised CT state in highly polar solvent. You can make a Lippert-Mataga plot to find the transition dipole moment etc.

This is all laid out in the paper (full text is up loaded)

Intramolecular charge transfer assisted by conformational changes in the excited state of fluorene-dibenzothiophene-S,S-dioxide co-oligomers.

Fernando B Dias, Sam Pollock, Gordon Hedley, Lars-Olof Pålsson, Andy Monkman, Irene I Perepichka, Igor F Perepichka, Mustafa Tavasli, Martin R Bryce

Hello, you can determine the free carrier concentration from a metal-insulator-semiconductor (MIS) capacitor. The structure is a little bit more complex because you need to add two more layers to obtain the capacitor. In this case you can run capacitance-voltage measurements and plot 1/C^2 to calculate the carrier concentration. You can refer to the attached paper for P3HT.

Electrochemically, e.g., via cyclic voltammetry

The technique provided by Dr David Cahen is direct and powerful. I think this is the best one, in general. Dr Andy Monkman's method also works, it is a qualitatiive one, but less quantitative. Which method is better, it depends on what you want to know. Since you have PL instrument, Dr Andy Monkman's method is practical for you.

As an additional, you can use the laser method to treat your conjugated materials. The laser induced change in the refractive index will be larger in the donor-acceptor compounds in the comparison with that without donor-acceptor interaction.

Please see. for example:

1. N. V. Kamanina, S. V. Serov, N. A. Shurpo, S. V. Likhomanova, D. N. Timonin, P. V. Kuzhakov, N. N. Rozhkova, I. V. Kityk, K. J. Plucinski, D. P. Uskokovic, “Polyimide-fullerene nanostructured materials for nonlinear optics and solar energy applications”, J Mater Sci: Mater Electron, DOI 10.1007/s10854-012-0625-9, published on-line 26 January 2012.

2. N.V. Kamanina, “Nonlinear optical study of fullerene-doped conjugated systems: new materials for nanophotonics applications”, Proceedings of the NATO Advanced Research Workshop on Organic Nanophotonics, v. II/100, pp. 177-192 (2003)

3. N.V. Kamanina, “Fullerene-dispersed liquid crystal structure: dynamic characteristics and self-organization processes” Physics-Uspekhi 48 (4), 419-427 (2005). DOI:10.1070/PU2005v048n04ABEH002101 Published: APR 200

David Cahen is recognized guru in this field, I advice you to trace his publications to get the answer to you question. Also the UPS, and even Kelvin probe could be used. It was shown Shlomo Yitchaik's publications (who originate from the same group) that both workfunction and band bending zones , which you could obtain through these techniques, in materials composed of molecular dipoles are proportional to strength of molecular dipole, so you could just use the "calibration curve". Note that Kelvin probe is 100 years old technique and could be easily used in low budget projects.

Thanks Vladimir Burtman.

Alex, you are very welcome, all people here are to help each other. Your question belong to the field which is well developed, and you could see this through responses you got, so there is really no need to re-invent the wheel. Please let me know if you will require more info, Good luck!

A cautionary note on the use of a Kelvin probe. the measurement is VERY VERY sensitive to many external conditions, the tip profile temperature etc etc. We have found that each system gives it's own set of errors and it is really hard to make comparative measurements.

I agree with Andy Kelvin probe is very sensitive to environment. It is clear why: Kelvin probe directly excite molecular dipoles and these are sensitive of coerce to humidity (react directly with free chemical cation-carry radicals), temperature (change dynamic of these interactions), tip (change electronic environment) etc. It is always worth to use the set of samples with different molecular dipoles to check that the trend is consistent and to compare your results to other reports.

I t can be determined by Cyclic Voltammetry

Hi,

I am using ToF-Sims trying to get infotmation about the composition of the photoactive layer (donnor-acceptor) e.g. their chemical composition before and after photoageing. I am just interesting to see how materials are oxidized analyzing their specific ions fragments. Therefore, this is not so easy since Sims will give you the same composition after fragmentation before and after degradation and also the fact that the technique is semi-quantitative and not the best when interesting to acquire information which are specific to each of the material when they are blended. Anyway it depend to the context and what do you really want to observe. In my case i can mange since i investigate a fresh and aged blend layers.

Hope that help you

Cheers

You can even characterize the optical properties (n+k) of thin film (semitransparent material) via spectroscopic ellipsometry.

Best regards

Christian