Substrate/semiconductor interface effects on the emission efficiency of luminescent polymers


Autoria(s): THEREZIO, Eralci M.; PIOVESAN, Erick; ANNI, Marco; SILVA, R. A.; OLIVEIRA JUNIOR, Osvaldo Novais de; MARLETTA, Alexandre
Contribuinte(s)

UNIVERSIDADE DE SÃO PAULO

Data(s)

19/04/2012

19/04/2012

2011

Resumo

The importance of interface effects for organic devices has long been recognized, but getting detailed knowledge of the extent of such effects remains a major challenge because of the difficulty in distinguishing from bulk effects. This paper addresses the interface effects on the emission efficiency of poly(p-phenylene vinylene) (PPV), by producing layer-by-layer (LBL) films of PPV alternated with dodecylbenzenesulfonate. Films with thickness varying from similar to 15 to 225 nm had the structural defects controlled empirically by converting the films at two temperatures, 110 and 230 degrees C, while the optical properties were characterized by using optical absorption, photoluminescence (PL), and photoluminescence excitation spectra. Blueshifts in the absorption and PL spectra for LBL films with less than 25 bilayers (<40-50 nm) pointed to a larger number of PPV segments with low conjugation degree, regardless of the conversion temperature. For these thin films, the mean free-path for diffusion of photoexcited carriers decreased, and energy transfer may have been hampered owing to the low mobility of the excited carriers. The emission efficiency was then found to depend on the concentration of structural defects, i.e., on the conversion temperature. For thick films with more than 25 bilayers, on the other hand, the PL signal did not depend on the PPV conversion temperature. We also checked that the interface effects were not caused by waveguiding properties of the excited light. Overall, the electronic states at the interface were more localized, and this applied to film thickness of up to 40-50 nm. Because this is a typical film thickness in devices, the implication from the findings here is that interface phenomena should be a primary concern for the design of any organic device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3622143]

CNPq

Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

FAPEMIG

INEO/MCT Ministério de Ciência e Tecnologia (Brazil)

Identificador

JOURNAL OF APPLIED PHYSICS, v.110, n.4, 2011

0021-8979

http://producao.usp.br/handle/BDPI/16468

10.1063/1.3622143

http://dx.doi.org/10.1063/1.3622143

Idioma(s)

eng

Publicador

AMER INST PHYSICS

Relação

Journal of Applied Physics

Direitos

openAccess

Copyright AMER INST PHYSICS

Palavras-Chave #LIGHT-EMITTING-DIODES #CONJUGATED POLYMERS #ENERGY-TRANSFER #FILMS #PHOTOLUMINESCENCE #OLIGOMERS #Physics, Applied
Tipo

article

original article

publishedVersion