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Ultrafast energy transfer in ultrathin organic donor/acceptor blend.

ABSTRACT: It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10?nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pass transient absorption technique (TrAMP) that enables us to perform ultra high sensitive measurements, we find that the primary process upon photoexcitation is ultrafast energy transfer from P3HT to PCBM. The expected charge separation due to hole transfer from PCBM to P3HT occurs in the 100?ps timescale. The derived picture is much different from the accepted view of ultra-fast electron transfer at the polymer/PCBM interface and provides new directions for the development of efficient devices.

SUBMITTER: Kandada AR

PROVIDER: S-EPMC3691563 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Ultrafast energy transfer in ultrathin organic donor/acceptor blend.

Kandada Ajay Ram Srimath AR Grancini Giulia G Petrozza Annamaria A Perissinotto Stefano S Fazzi Daniele D Raavi Sai Santosh Kumar SS Lanzani Guglielmo G

Scientific reports 20130101

It is common knowledge that poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend, a prototype system for bulk heterojunction (BHJ) solar cells, consists of a network of tens of nanometers-large donor-rich and acceptor-rich phases separated by extended finely intermixed border regions where PCBM diffuse into P3HT. Here we specifically address the photo-induced dynamics in a 10 nm thin P3HT/PCBM blend that consists of the intermixed region only. Using the multi-pas ...[more]

PMID: 23797845

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Project description:EPR spectroscopy is an important spectroscopic method for identification and characterization of radical species involved in many biological reactions. The tyrosyl radical is one of the most studied amino acid radical intermediates in biology. Often in conjunction with histidine residues, it is involved in many fundamental biological electron and proton transfer processes, such as in the water oxidation in photosystem II. As biological processes are typically extremely complicated and hard to control, molecular bio-mimetic model complexes are often used to clarify the mechanisms of the biological reactions. Here we present theoretical calculations to investigate the sensitivity of magnetic resonance parameters to proton-coupled electron transfer events, as well as conformational substates of the molecular constructs which mimic the tyrosine-histidine (Tyr-His) pairs found in a large variety of proteins. Upon oxidation of the phenol, the Tyr analogue, these complexes can perform not only one-electron one-proton transfer (EPT), but also one-electron two-proton transfers (E2PT). It is shown that in aprotic environment the gX-components of the electronic g-tensor are extremely sensitive to the first proton transfer from the phenoxyl oxygen to the imidazole nitrogen (EPT product), leading to a significant increase of the gX-value of up to 0.003, but are not sensitive to the second proton transfer (E2PT product). In the latter case the change of the gX-value is much smaller (ca. 0.0001), which is too small to be distinguished even by high frequency EPR. The 14N hyperfine values are also too similar to allow differentiation between the different protonation states in EPT and E2PT. The magnetic resonance parameters were also calculated as a function of the rotation angles around single bonds. It was demonstrated that rotation of the phenoxyl group results in large positive changes (>0.001) in the gX-values. Analysis of the data reveals that the main source of these changes is related to the strength of the H-bond between phenoxyl oxygen and the proton(s) on N1 and N2 positions of the imidazole.

Dataset Information

Ultrafast energy transfer in ultrathin organic donor/acceptor blend.

Publications

Ultrafast energy transfer in ultrathin organic donor/acceptor blend.

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