Conjugated exciton diffusion length

D. E. Markov, E. Amsterdam, P. W. M. Blom, A. B. Sieval, J. C. Hummelen, Accurate Measurement of the Exciton Diffusion Length in a Conjugated Polymer Using a Heterostructure with a Side-Chain Cross-Linked Fullerene Layer. The Journal of Physical Chemistry A 2005,109, 5266-5274. 

Conjugated copolymers where suitable donor and acceptor segments or even blocks are chemically linked, have been demonstrated to fine tune the optoelectronic properties (e.g. bandgap, transport properties) and morphological features (e.g. phase segregation at a scale to match exciton diffusion length) to improve the optoelectronic performance and stability of related OPV devices. In particular, the donor-acceptor type alternating copolymers and donor-acceptor type block copolymers have special relevance in the context of above discussions. 

Markov, D.E., Amsterdam, E., Blom, P.W.M., Sieval, A.B., and Hummelen, J.C. (2005) Accurate measurement of the exciton diffusion length in a conjugated polymer using a heterostructure with a side-chain cross-linked fullerene layer. 

The conjugated polymers employed in BHJ solar cells have exciton diffusion lengths ranging from 5 to 20 nm [54], but the proximity between donor and... 

Fig. 18 Mechanism for donor-acceptor heterojunction solar cells. (7) Photoexitation of the donor to generate a Coulomb correlated electron-hole pair, an exciton. (2) Exciton diffusion to the D-A interface. A distance longer than the maximum diffusion length (max LD) will lead to relaxation of the exciton. (3) Bound exciton dissociation at the D-A interface to form a geminate pair. (4) Free charge transportation and collection at electrodes. Reprinted with pamission from ACS, Y.-J. Cheng, S.-H. Yang, and C.-S. Hsu, Synthesis of Conjugated Polymtax for Organic Solar Cell Applications Chem. Rev. 2009, 109, 5868-5923...

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