Fullerene C70 as a p-type donor in organic photovoltaic cells

Zhuang, Taojun; Sano, Takeshi; Hong, Ziruo; Li, Gang; Yang, Yang; Kido, Junji

doi:10.1063/1.4894637

Cited by 17 publications

(14 citation statements)

References 30 publications

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“…HATCN has been shown to effi ciently dissociate excitons in organic photovoltaics due to its deep energy levels. [ 22 ] The energy levels at the NPD/HATCN interface are even more favorable for charge transfer, and we assume that exciton dissociation is also active there. The J -V characteristics, electroluminescence (EL) spectra, external quantum effi ciency (EQE), and operational lifetime at an initial luminance of 3000 cd m −2 for devices A and B are shown in Figure 3 .…”

Section: Communicationmentioning

confidence: 99%

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

Coburn

Lee

Forrest

2016

Advanced Optical Materials

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local density of excitons, into both the PHOLED charge transport layers and the EML. This is, to our knowledge, the fi rst time that sensing layers have been used to measure charge and exciton leakage into transport layers, and to directly determine the dependence of charge balance and the extent of the exciton formation zone on current. Our results suggest a modifi ed structure with improved blocking characteristics leading to higher effi ciency and potentially longer device lifetime.An understanding of charge transport and the exciton density distribution is necessary to determine the effi cacy of a particular choice of blocking layer material. Charges injected at the electrodes are transported into the EML where they eventually recombine to form excitons, or are transported into an adjacent layer and lost to nonradiative recombination or are collected at the electrodes. Driftdiffusion with thermionic emission over energy barriers between layers can describe the charge balance and carrier distribution in the PHOLED [ 5,8,9 ] yielding the following expressionswith the boundary conditions ofand ( ) 0 a b i . Here, x = 0 corresponds to the position at the anode side of the EML, and x = L at the cathode. Also, E(x,t) is the electric fi eld at x and time t , q is the charge, k is Boltzmann's constant, T is the temperature, and ε is the dielectric constant of the material. Also, J x t n ( , ) is the electron current density, x t n ( , ) μ is its mobility, n x t ( , ) is the electron density, p x t ( , ) is the hole density, Va is the applied voltage, Vbi is the built-in voltage, E 0 is a reference electric fi eld, φ is the frontier orbital energy difference across an interface, and t E t d ( ) ( ) φ Δ = is the potential difference across the interface of width d . The hole current density, J x t p ( , ), is found using an expression analogous to Equation ( 1) . The Einstein relation is used to relate mobility to the diffusion constant, and thermionic emission over barriers has a Poole-Frenkel type fi eld dependence common to organics. [ 10 ] The solution to these equations determine the charge balance, given by Charge Balance and Exciton Confi nement in Phosphorescent Organic Light Emitting DiodesCaleb Coburn , Jaesang Lee , and Stephen R. Forrest* DOI: 10.1002/adom.201600067We study the charge balance and exciton confi nement in blue phosphorescent organic light emitting devices (PHOLEDs) by strategically placing ultrathin, red phosphorescent layers whose emission intensity is proportional to the local density of excitons at several locations within the device. Based on measured exciton distributions, we derive a model for understanding those materials properties that determine charge and exciton transport and confi nement, as well as for interpreting the experimental exciton profi les. We fi nd that triplet exciton leakage results from the very large energy gaps characteristic of blue phosphors, and demonstrate increased lifetime and efficiency in devices with improved exciton confi nement within the diode emission...

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Section: Communicationmentioning

confidence: 99%

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

Coburn

Lee

Forrest

2016

Advanced Optical Materials

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“…Inspired from the Sibased solar cell, a hybrid Si/C 60 material-based device was fabricated and tested by Yun et al [232] that demonstrated a power conversion efficiency of 8.43%. Zhuang et al [233] have studied the performance of C 70 as a p-type electron donor in organic solar cells with 2.83% power conversion efficiency. Although this value is quite low, by exploring the other types of electron acceptors, it could possibly improve the efficiency significantly.…”

Section: Batteriesmentioning

confidence: 99%

Self‐Assembled Fullerene Nanostructures: Synthesis and Applications

Baskar

Benzigar

Talapaneni

et al. 2021

Adv Funct Materials

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Functionalized fullerene nanostructures are a distinct class of materials that exhibit the combined properties of both fullerene and nanostructures including excellent optoelectronic features, modified band edges, high electron affinity, fast charge transfer capabilities, and tunable structural and textural properties. These fascinating properties allow for their utilization in many applications such as polymer solar cells, photovoltaics, photocatalysis, photodynamic therapy, electrocatalysis, environmental remediation, and drug and gene delivery. Numerous synthesis methods and anchoring groups are employed for functionalized fullerenes with nanostructures by using convergent bottom-up and top-down strategies. The supramolecular self-assembly and functionalization of fullerenes through robust chemistry approaches such as surface oxidation, grafting, polymer coating, doping of metals/nonmetal heteroatoms, noncovalent modification with 2D materials and nanoparticle attachment result in achieving fine control over its surface and bulk properties, including increased solubility, wettability, electron transport, acid-base properties, adsorption, electronic conductivity, and light absorption. This review analyzes the salient developments in the fabrication of nanostructured fullerenes and their functionalized derivatives for many applications including adsorption, catalysis, sensors, energy storage, solar cells, drug delivery, magnetic and superconducting devices. The contents of this review will allow the readers to cherish exciting possibilities and opportunities in field of functionalized nanofullerenes.

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“…In our previous studies on fullerene donors, we demonstrated a charge transfer process occurring between C 70 and HAT-CN [16]. In the BHJ cells with compound buffer layers, 5 nm HAT-CN is in direct contact with DBP and the C 70 blend active layer contains a high ratio of C 70 .…”

Section: Resultsmentioning

confidence: 97%

“…The materials used in our devices, including MoO 3 , 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) [16], DBP [17], C 70 , and bathocuproine (BCP) are commercially available. MoO 3 and BCP were used as received.…”

Section: Methodsmentioning

confidence: 99%

Efficient small molecule-based bulk heterojunction photovoltaic cells with reduced exciton quenching in fullerene

Zhuang

Sano

Kido

2015

Organic Electronics

Self Cite

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a b s t r a c tMost highly efficient small molecule-based bulk heterojunction (BHJ) photovoltaic cells contain a large concentration of fullerene in their blend active layers. However, the excitons generated in fullerene can seriously quench at the surface of the commonly used MoO 3 buffer layer, becoming a key limitation to the photovoltaic performance of these cells. In this study, we've investigated various anode buffer layers in the thermally evaporated tetraphenyldibenzoperiflanthene (DBP) and C 70 -based BHJ cells with high C 70 concentration. It's been found that obviously enhanced power conversion efficiency (PCE) of up to 6.26% can be obtained in DBP and C 70 -based BHJ cells via simply replacing the MoO 3 buffer by poly(3, 4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS), which is also a commonly used anode buffer material in polymer-based BHJ cells. Photoluminescence spectra results have confirmed the suppression of exciton quenching at the anode interface by inserting this PEDOT: PSS buffer. Moreover, after adding a C 70 interlayer for better electron extraction and the further suppression of exciton quenching, the DBP and C 70 -based M-i-n photovoltaic cells show a remarkable PCE of 7.04% under illumination with 100 mW/cm 2 , AM 1.5G simulated solar light.

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Fullerene C70 as a p-type donor in organic photovoltaic cells

Cited by 17 publications

References 30 publications

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

Charge Balance and Exciton Confinement in Phosphorescent Organic Light Emitting Diodes

Self‐Assembled Fullerene Nanostructures: Synthesis and Applications

Efficient small molecule-based bulk heterojunction photovoltaic cells with reduced exciton quenching in fullerene

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