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Synthesis, structure, and opto-electronic properties of organic-based nanoscale heterojunctions.

Rezek B, Cermák J, Kromka A, Ledinský M, Hubík P, Mareš JJ, Purkrt A, Cimrová V, Fejfar A, Kočka J - Nanoscale Res Lett (2011)

Bottom Line: We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties.These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data.We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics ASCR, v,v,i,, Cukrovarnická 10, 16200 Prague 6, Czech Republic. rezek@fzu.cz.

ABSTRACT
Enormous research effort has been put into optimizing organic-based opto-electronic systems for efficient generation of free charge carriers. This optimization is mainly due to typically high dissociation energy (0.1-1 eV) and short diffusion length (10 nm) of excitons in organic materials. Inherently, interplay of microscopic structural, chemical, and opto-electronic properties plays crucial role. We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties. By adjusting parameters of contact- and tapping-mode atomic force microscopy (AFM), we perform morphologic and mechanical characterizations (nanoshaving) of organic layers, measure their electrical conductivity by current-sensing AFM, and deduce work functions and surface photovoltage (SPV) effects by Kelvin force microscopy using high spatial resolution. These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data. We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond.

No MeSH data available.


Related in: MedlinePlus

Multidimensional microscopic characteristics (images and spatial profiles) of the organic heterostructure blend made of fullerene C60 and poly[(2,7-(9,9-dihexa)fluorene)-co-(1,4-(2,5-didecylaminoketo) phenylene)]: (a) tapping-mode AFM surface morphology, (b) KFM surface potential, (c) micro-Raman intensity at 1468 cm-1, (d) micro-Raman intensity at 1400 cm-1, and (e) local conductivity as measured by CS-AFM (negative bias voltage applied on the sample). Positions of the profiles in the images are indicated by the dashed lines and arrows.
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Figure 2: Multidimensional microscopic characteristics (images and spatial profiles) of the organic heterostructure blend made of fullerene C60 and poly[(2,7-(9,9-dihexa)fluorene)-co-(1,4-(2,5-didecylaminoketo) phenylene)]: (a) tapping-mode AFM surface morphology, (b) KFM surface potential, (c) micro-Raman intensity at 1468 cm-1, (d) micro-Raman intensity at 1400 cm-1, and (e) local conductivity as measured by CS-AFM (negative bias voltage applied on the sample). Positions of the profiles in the images are indicated by the dashed lines and arrows.

Mentions: In spite of observed quenching of photoluminescence compared to polymer layer without the C60, the composite layer exhibited low PV power conversion efficiency (Isc ~ 2 nA, Voc ~ 5 mV, η ~ 0.06%) [42]. AFM morphology (Figure 2a) revealed a relatively flat and smooth surface (RMS roughness: 4 nm) which was covered with two types of clusters (lateral size either 100 nm or several μm) and dendrites (more than 10 μm). Electrical potential map obtained by KFM at the same area is shown in Figure 2b. KFM detected the highest surface potential (up to 50 mV) in the central part of the dendrite and the lowest surface potential (as low as -150 mV) in its immediate surrounding. Farther surroundings exhibit the potential between these two values. Typical value is around - 30 mV. Also fluctuations related with small clusters are seen in topography. As the layer is made of two materials, the observed variations in surface potential most likely correspond to variations in local chemical composition. The two extreme potential levels may correspond to individual materials while the intermediate potential is related to the blend.


Synthesis, structure, and opto-electronic properties of organic-based nanoscale heterojunctions.

Rezek B, Cermák J, Kromka A, Ledinský M, Hubík P, Mareš JJ, Purkrt A, Cimrová V, Fejfar A, Kočka J - Nanoscale Res Lett (2011)

Multidimensional microscopic characteristics (images and spatial profiles) of the organic heterostructure blend made of fullerene C60 and poly[(2,7-(9,9-dihexa)fluorene)-co-(1,4-(2,5-didecylaminoketo) phenylene)]: (a) tapping-mode AFM surface morphology, (b) KFM surface potential, (c) micro-Raman intensity at 1468 cm-1, (d) micro-Raman intensity at 1400 cm-1, and (e) local conductivity as measured by CS-AFM (negative bias voltage applied on the sample). Positions of the profiles in the images are indicated by the dashed lines and arrows.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211298&req=5

Figure 2: Multidimensional microscopic characteristics (images and spatial profiles) of the organic heterostructure blend made of fullerene C60 and poly[(2,7-(9,9-dihexa)fluorene)-co-(1,4-(2,5-didecylaminoketo) phenylene)]: (a) tapping-mode AFM surface morphology, (b) KFM surface potential, (c) micro-Raman intensity at 1468 cm-1, (d) micro-Raman intensity at 1400 cm-1, and (e) local conductivity as measured by CS-AFM (negative bias voltage applied on the sample). Positions of the profiles in the images are indicated by the dashed lines and arrows.
Mentions: In spite of observed quenching of photoluminescence compared to polymer layer without the C60, the composite layer exhibited low PV power conversion efficiency (Isc ~ 2 nA, Voc ~ 5 mV, η ~ 0.06%) [42]. AFM morphology (Figure 2a) revealed a relatively flat and smooth surface (RMS roughness: 4 nm) which was covered with two types of clusters (lateral size either 100 nm or several μm) and dendrites (more than 10 μm). Electrical potential map obtained by KFM at the same area is shown in Figure 2b. KFM detected the highest surface potential (up to 50 mV) in the central part of the dendrite and the lowest surface potential (as low as -150 mV) in its immediate surrounding. Farther surroundings exhibit the potential between these two values. Typical value is around - 30 mV. Also fluctuations related with small clusters are seen in topography. As the layer is made of two materials, the observed variations in surface potential most likely correspond to variations in local chemical composition. The two extreme potential levels may correspond to individual materials while the intermediate potential is related to the blend.

Bottom Line: We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties.These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data.We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Physics ASCR, v,v,i,, Cukrovarnická 10, 16200 Prague 6, Czech Republic. rezek@fzu.cz.

ABSTRACT
Enormous research effort has been put into optimizing organic-based opto-electronic systems for efficient generation of free charge carriers. This optimization is mainly due to typically high dissociation energy (0.1-1 eV) and short diffusion length (10 nm) of excitons in organic materials. Inherently, interplay of microscopic structural, chemical, and opto-electronic properties plays crucial role. We show that employing and combining advanced scanning probe techniques can provide us significant insight into the correlation of these properties. By adjusting parameters of contact- and tapping-mode atomic force microscopy (AFM), we perform morphologic and mechanical characterizations (nanoshaving) of organic layers, measure their electrical conductivity by current-sensing AFM, and deduce work functions and surface photovoltage (SPV) effects by Kelvin force microscopy using high spatial resolution. These data are further correlated with local material composition detected using micro-Raman spectroscopy and with other electronic transport data. We demonstrate benefits of this multi-dimensional characterizations on (i) bulk heterojunction of fully organic composite films, indicating differences in blend quality and component segregation leading to local shunts of photovoltaic cell, and (ii) thin-film heterojunction of polypyrrole (PPy) electropolymerized on hydrogen-terminated diamond, indicating covalent bonding and transfer of charge carriers from PPy to diamond.

No MeSH data available.


Related in: MedlinePlus