The Mechanism for Ultrafast Electron Transfer

The field of bulk heterojunction (BHJ) solar cells was created as a result of the demonstration of ultrafast charge transfer. Ultrafast observations of pho-toinduced infrared active vibrational modes (IRAV) associated with polaron formation unambiguously established the ultrafast photogeneration of eharge carriers in BHJ materials.  

Our initial discovery of ultrafast electron transfer occurred in late 1992. It was a discovery based purely on curiosity. At that time, we had been working on the optical properties of semiconducting polymers for many years. Then, the fullerenes were discovered. Prof. Serdar Sariciftci was a Post-doc. 

Polymer Photovoltaics Materials, Physics, and Device Engineering 

Photogenerated electron transfer reactions in chemistry typically occur on a timescale significantly greater than the decay timescale of coherent processes. Electron transfer reactions fail this criterion in poly(phenylen-evinylene) based polymers, for which the photogenerated coherent wave-function persists for 25 fs (in solution), and electron transfer occurs in =45 fs in the solid BHJ material. In P3HT, the coherent wavefunction persists for 100 fs in solution, while the electron transfer timescale is 100 fs in the BHJ material. It is therefore necessary to develop testable hypotheses regarding the meehanism of eleetron transfer in situations where a coherent photoexeited state is involved in the ultrafast electron transfer in bulk heterojunetion solar eells. 

Schrodinger equation that describes the nanostructured organic photovoltaic blend. Thus, there is an immediate probability amplitude for finding a photoexcitation near a heterojunction boundary, thereby enabling ultrafast charge transfer (in the femtosecond regime) over relatively long distances. 

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