The electron transfer processes in organic molecules were examined using ultrafast time resolved spectroscopies. The two-photon ionization of trans-stilbene was analyzed using femtosecond, excited state, electronic and vibrational spectroscopies. It was found that the ionization process occurs instantaneously, but the charge separation and the charge recombination are competing pathways. The charge separation was found to occur within 20 ps while the charge recombination occurs in 50 ps. To further characterize these processes in trans-stilbene and to measure the electron transfer processes between poly(3-hexylthiophene) (P3HT) and N,N'-dioctyl-3,4,9,10-perylenedicarboximide (PDI-C8) the technique of femtosecond stimulated Raman spectroscopy (FSRS) was developed in order to measure the excited state Raman spectrum. It was found that the excited state Raman spectrum contains many features from states and processes not associated with the excited state. Due to the complications with the measurement of the FSRS spectrum for molecules, the electron transfer dynamics between P3HT and PDI-C8 were measured using femtosecond, excited state, visible and infrared spectroscopies. It was found that no electron transfer occurs from the excited state of PDI-C8 to the P3HT. It was also found that from the excited state of P3HT and electron is transferred to PDI-C8 within the time resolution of the laser (<100 fs). The back electron transfer from PDI-C8-. to P3HT+. occurs in approximately 350 ps. It is expected that this back electron transfer is the limiting factor for the efficiency of PDI-C8:P3HT organic photovoltaic devices.
|Advisor:||Gustafson, Terry, Epstein, Arthur|
|Commitee:||Chin, Yu-Ping, Singer, Sherwin|
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 78/11(E), Dissertation Abstracts International|
|Keywords:||Electron transfer, Organic photovoltaics, Photochemistry, Ultrafast spectroscopy|
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