Photovoltaic effect and electrically detected electron spin resonance of a H2-phthalocyanine/C60 heterojunction

Hiromitsu, Ichiro; Kaimori, Yoshiaki; Ito, Takashi

doi:10.1016/s0038-1098(97)00344-x

Cited by 12 publications

(9 citation statements)

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“…The photovoltaic effect occurs by a photo-excitation of H 2 Pc and/or C 60 in the interface region, followed by a charge separation in which the electron and the hole diffuse to the C 60 ͑acceptor͒ and the H 2 Pc ͑donor͒ layers, respectively. A preliminary EDESR study was also done previously 5 in which a decrease of the photocurrent by a factor of ϳ10 Ϫ4 was observed by applying a resonant microwave. In the present study, a more complete EDESR measurement is done with an improved sensitivity.…”

Section: Introductionmentioning

confidence: 88%

“…The recombination probability is spin dependent, so that it is affected by the occurrence of the ESR transition, which alters the spin states. The sensitivity of EDESR is 10 3 -10 4 times higher than conventional ESR, [5][6][7] so that EDESR is a powerful experimental technique to study the recombination mechanism in small-volume systems like thin films or heterojunctions.…”

Section: Introductionmentioning

confidence: 99%

“…The photovoltaic characteristics of the H 2 Pc/C 60 heterojunction have been reported recently: 5 The H 2 Pc/C 60 is a typical donor-acceptor-type 11 photocell, with a conversion efficiency of 0.02%. The photovoltaic effect occurs by a photo-excitation of H 2 Pc and/or C 60 in the interface region, followed by a charge separation in which the electron and the hole diffuse to the C 60 ͑acceptor͒ and the H 2 Pc ͑donor͒ layers, respectively.…”

Section: Introductionmentioning

confidence: 99%

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Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60heterojunctions

et al. 1999

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Spin-dependent recombination of photoinduced carriers in H 2 -phthalocyanine (H 2 Pc͒/C 60 heterojunctions is studied by electrically detected electron-spin resonance ͑EDESR͒ spectroscopy. The EDESR spectrum of the H 2 Pc/C 60 consists of two components A and B, the g values of which are 2.0018Ϯ0.0002 and 2.0010Ϯ0.0002, respectively. The two components are attributed to exchange-coupled localized electron-hole pairs trapped at different types of recombination centers. Component A has spin-flip satellites due to an interaction between the electron ͑or hole͒ spin, and its surrounding nuclear spins of protons which belong to the H 2 Pc rings. From the satellite intensity, the distance between the electron ͑or hole͒ and the protons is estimated to be 4.33Ϯ0.25 Å, indicating that the localized pairs for the component A locate close to the H 2 Pc rings. The spin dynamics of the localized pairs for the component A is studied by a microwave recovery experiment, in which the time dependence of the EDESR signal intensity is measured after turning the resonant microwave on and off. A theoretical model of the spin-dependent recombination of the exchange-coupled electron-hole pair is proposed with which the experimental results of the microwave recovery are explained. By a theoretical analysis, it is found that Rտ1ϫ10 6 s Ϫ1 and DϩW sl ϭ6.2 (Ϯ0.8)ϫ10 4 s Ϫ1 for component A at room temperature, where R is the recombination rate of the localized pair in the S z ϭ0 triplet sublevel, and D and W sl are the dissociation and the spin-lattice relaxation rates, respectively, of the pairs in the triplet sublevels. The photocurrent I 2 that is caused by the dissociation of the localized pairs for component A is about 5% of the total photocurrent.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60heterojunctions

et al. 1999

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“…The CuPc and H 2 Pc used in our bulk OHJs are also widely used in OSCs, and they have a similar molecular and electronic structure to ZnPc. 105,106 By using these to construct bulk OHJs with C 60 as the CGLs in tandem OLEDs, we found that a similar power efficiency improvement can also be achieved ( Table 2). This indicates that the bulk OHJs as CGLs are also a viable option for the fabrication of high-performance tandem OLEDs.…”

Section: Design Conceptmentioning

confidence: 79%

Organic semiconductor heterojunctions as charge generation layers and their application in tandem organic light-emitting diodes for high power efficiency

Chen

2012

J. Mater. Chem.

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Organic light-emitting diodes (OLEDs) can convert injected charge into photons. The upper conversion limit of single-unit OLEDs is at most one photon per injected electron. Alternatively, tandem OLEDs that vertically stack several single-unit OLEDs via charge generation layers (CGLs) can convert one injected electron into multiple photons, thus achieving greater brightness and current efficiency with a lower current. However, since the driving voltage consumed by conventional tandem devices scales linearly with the number of electroluminescent units, the resulting power consumption would be the same for both the single-unit and tandem OLEDs to obtain the same luminescence; this means that the power efficiency cannot be greatly increased for such tandem devices. Recently we found that using buffer-modified intrinsic organic semiconductor heterojunctions (OHJs) as the CGLs significantly enhanced the power efficiency of the fabricated tandem OLEDs, which was previously suggested to be difficult for tandem devices. In this feature article, we review the recent advances of tandem OLEDs based on OHJs as the CGLs, including the design concept and basic requirements of the energy levels and mobility of involved organic semiconductors. Our results show that the use of OHJs as CGLs is a universal concept for the fabrication of tandem OLEDs with high power efficiency. We believe that the concept of OHJs opens new perspectives for the rational design of CGLs to realize tandem devices with unprecedented improvement in power efficiency. In particular, it has great potential for use in the fabrication of tandem white OLEDs (WOLEDs) for solid-state-lighting. Yonghua Chen Dr Yonghua Chen received his BE degree in chemistry from Inner Mongolia University in 2006 and then joined Dr Dongge Ma's group at Changchun Institute of Applied Chemistry, Chinese Academy of Sciences (CAS), where he obtained his Ph.D. in polymer chemistry and physics in 2011. Currently, he is doing his postdoctoral research at Wake Forest University. His research interests include tandem organic light-emitting diodes and field-induced polymer electroluminescent devices for flat panel displays and solidstate lighting.

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“…Em particular, a técnica de Ressonância Magnética Detectada Eletricamente (RMDE) tem sido empregada com sucesso no estudo dos processos de transporte e recombinação em semicondutores cristalinos [18,19,20,21], em semicondutores amorfos, micro ou policristalinos [22,23,24,25,26,27,28,29,30] e em semicondutores orgânicos [31,32,33,34,35,36,37]. aplicá-la a dispositivos poliméricos [36,37].…”

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Estudo de processos de transporte eletrônico em dispositivos a base de semicondutores orgânicos

Castro¹

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DEDICATÓRIA iiDedico este trabalho à minha família, em especial à minha querida esposa, Mabel, a meu irmão, Gustavo, e aos meus pais, Sérgio e Inês, que, com carinho, sempre me apoiaram e me incentivaram. AGRADECIMENTOS iiiAo Prof. Carlos F. O. Graeff, meu orientador, pela inestimável orientação, pelas oportunidades apresentadas e, principalmente, pela amizade e confiança em mim depositadas.Ao Prof. Roberto Mendonça Faria, pelo apoio irrestrito a este trabalho.Ao amigo Dr. Lucas Fugikawa, pelas inestimáveis contribuições a este trabalho, pelo auxílio na preparação dos diodos de MEH-PPV e nas medidas de impedância e por ter cedido a figura 7.6, assim como pelas inúmeras discussões.Ao amigo George Silva, pelas inúmeras discussões e pelo inestimável auxílio no aprendizado da técnica de RMDE.Ao amigo Dr. Paulo Bueno, pela recente amizade, pelas ótimas discussões e pelo inestimável auxílio sobre os resultados de impedância.Ao Dr. Frank Nüesch pela preparação dos OLEDs de Alq 3 e pelas ótimas discussões.Ao amigo Carlão e à Dr. Débora Balogh, pelas dicas e pela ajuda em todas as horas.Aos Professores e amigos Dr. Francisco E. G. Guimarães e Dr. Alexandre Marletta, por terem me introduzido à pesquisa científica, assim como pela sua amizade e confiança.Aos colegas e professores do grupo de polímeros e do grupo ressomat, pelo bom ambiente de trabalho e pelas discussões oportunas. Em especial, ao Jair Junior, ao Célio Borges, ao Edivaldo Queiroz e ao Dr. Rodrigo Bianchi, pela amizade, pelas discussões e pela ajuda em todas as horas.Ao CNPQ pela bolsa de mestrado e ao IMMP/MCT pelo auxílio financeiro.

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Photovoltaic effect and electrically detected electron spin resonance of a H2-phthalocyanine/C60 heterojunction

Cited by 12 publications

References 12 publications

Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60heterojunctions

Spin-dependent recombination of photoinduced carriers in phthalocyanine/C60heterojunctions

Organic semiconductor heterojunctions as charge generation layers and their application in tandem organic light-emitting diodes for high power efficiency

Estudo de processos de transporte eletrônico em dispositivos a base de semicondutores orgânicos

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