Limits...
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

Electronic transport characteristics and scheme of PPy-diamond hetero-junction. (a) Current-voltage characteristics of the PPy-diamond system in the dark and under white light illumination. (b) Conceptual drawing of charge transfer of photogenerated holes from PPy to diamond where they support the in-plane conductivity.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3211298&req=5

Figure 9: Electronic transport characteristics and scheme of PPy-diamond hetero-junction. (a) Current-voltage characteristics of the PPy-diamond system in the dark and under white light illumination. (b) Conceptual drawing of charge transfer of photogenerated holes from PPy to diamond where they support the in-plane conductivity.

Mentions: The manner in which these holes contribute also to sub-band gap optical excitation of free holes in diamond depends on many factors [45]. Therefore, we characterized electronic transport properties of the PPy-diamond system by I(V) measurements both in the dark and under the white light illumination. In the dark, the diamond channel with grafted PPy on top was highly electrically insulating as expected due to the missing H termination. The conductivity does not recover even when we remove PPy and expose the diamond surface to the ambient air (adsorbates) again. Hence, the adsorbates play no role in this effect. Under the white light illumination, the channel with PPy turned electrically conductive (approximately 100 pA when 1 V is applied, see Figure 9a). Such changes of electrical current occur within 1 s and are reproducible [46]. This is in agreement with the fast changes in the surface potential as shown in Figure 7b.


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)

Electronic transport characteristics and scheme of PPy-diamond hetero-junction. (a) Current-voltage characteristics of the PPy-diamond system in the dark and under white light illumination. (b) Conceptual drawing of charge transfer of photogenerated holes from PPy to diamond where they support the in-plane conductivity.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: Electronic transport characteristics and scheme of PPy-diamond hetero-junction. (a) Current-voltage characteristics of the PPy-diamond system in the dark and under white light illumination. (b) Conceptual drawing of charge transfer of photogenerated holes from PPy to diamond where they support the in-plane conductivity.
Mentions: The manner in which these holes contribute also to sub-band gap optical excitation of free holes in diamond depends on many factors [45]. Therefore, we characterized electronic transport properties of the PPy-diamond system by I(V) measurements both in the dark and under the white light illumination. In the dark, the diamond channel with grafted PPy on top was highly electrically insulating as expected due to the missing H termination. The conductivity does not recover even when we remove PPy and expose the diamond surface to the ambient air (adsorbates) again. Hence, the adsorbates play no role in this effect. Under the white light illumination, the channel with PPy turned electrically conductive (approximately 100 pA when 1 V is applied, see Figure 9a). Such changes of electrical current occur within 1 s and are reproducible [46]. This is in agreement with the fast changes in the surface potential as shown in Figure 7b.

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