Impact of doping on the density of states and the mobility in organic semiconductors

Zuo, Guangzheng; Abdalla, Hassan; Kemerink, Martijn

doi:10.1103/physrevb.93.235203

Cited by 88 publications

(96 citation statements)

References 32 publications

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“…Then, the relationship Σ ∝ n eff 0.5 is consistent with our result. It is also worth mentioning that our results are consistent with previous studies about the electrical characteristics of RGO with varying temperature measurements [42,43]. In order to estimate the effect of electric fields on the R , we mapped the R values at the bias voltages of 0.2 V and 2 V, as shown in the Fig.3a and 3b, respectively.…”

Section: Nanoscale Mapping Of Sheet−resistances and Noise−source Actisupporting

confidence: 89%

“…In this case, conducting domains and hopping of carriers can determine the conduction mechanism. On the other hand, at a room temperature, the insulating domains and trap-to-trap transition could contribute dominantly to the electrical conduction, which is consistent with our works[42,43]. These results provide important insights about the role of electronic traps as dominant noise−sources on the charge transports in different domains of RGO.…”

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confidence: 89%

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Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

Shekhar

Lee

Cho

et al. 2019

Carbon

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et al.. Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide. Carbon, Elsevier, 2019, 148, pp. ABSTRACTWe report a nanoscale mapping of noise-source-controlled transport characteristics in the domains of reduced graphene oxide by utilizing noise-source imaging strategies. In this method, current and noise images were measured simultaneously using a scanning noise microscopy and analyzed to map sheet−resistances (R ) and noise−source densities (n eff ). The maps showed the formation of conducting and insulating domains, where the insulating domains exhibited up to three-four orders of higher R and n eff than those of conducting domains. Interestingly, the sheet−conductance (Σ ) and n eff followed rather opposite power−law behaviors like Σ ∝ n eff −0.5 and Σ ∝ n eff 0.5 in conducting and insulating domains, respectively, which could be attributed to the difference in mesoscopic charge transport mechanisms controlled by n eff in domains. Notably, high biases resulted in the increased conductance (∆Σ ) and decreased noise−source density (∆n eff ) following a relationship like ∆Σ ∝−∆n eff 0.5 for both conducting and insulting domains, which could be explained by the passivation of noise−sources at high biases. Furthermore, ∆Σ versus ∆n eff plot on the annealing also followed a power−law dependence (∆Σ ∝−∆n eff 0.5 ) in conducting domains, which could be attributed to carrier generation on the annealing. Our results about mesoscopic charge transports could be significant advancements in fundamental researches and applications.

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Section: Nanoscale Mapping Of Sheet−resistances and Noise−source Actisupporting

confidence: 89%

supporting

confidence: 89%

Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

Shekhar

Lee

Cho

et al. 2019

Carbon

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“…This dependency was found to hold for both Miller-Abrahams and Marcus hopping rates, albeit with different prefactors. Zuo et al have shown that adhering to an E * that sits a fixed distance below the DOS maximum gives an accurate description of the conductivity even in the case that dopant ions give rise to an exponential tail in the DOS [17]. Hence, the modest shift in E * for NNH in Fig.…”

mentioning

confidence: 95%

“…In Refs. [17,18] the model has been benchmarked against kinetic Monte Carlo simulations and shown to accurately reproduce the measured conductivity of both intrinsic and doped OSCs over a wide concentration range, with minor deviations occurring at molar doping concentrations approaching 10%. For comparison with kinetic Monte Carlo simulations NNH was previously assumed, but the model can easily be modified to capture either NNH or VRH.…”

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confidence: 99%

Range and energetics of charge hopping in organic semiconductors

2017

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The recent upswing in attention for the thermoelectric properties of organic semiconductors (OSCs) adds urgency to the need for a quantitative description of the range and energetics of hopping transport in organic semiconductors under relevant circumstances, i.e., around room temperature (RT). In particular, the degree to which hops beyond the nearest neighbor must be accounted for at RT is still largely unknown. Here, measurements of charge and energy transport in doped OSCs are combined with analytical modeling to reach the univocal conclusion that variable-range hopping is the proper description in a large class of disordered OSC at RT. To obtain quantitative agreement with experiment, one needs to account for the modification of the density of states by ionized dopants. These Coulomb interactions give rise to a deep tail of trap states that is independent of the material's initial energetic disorder. Insertion of this effect into a classical Mott-type variable-range hopping model allows one to give a quantitative description of temperature-dependent conductivity and thermopower measurements on a wide range of disordered OSCs. In particular, the model explains the commonly observed quasiuniversal power-law relation between the Seebeck coefficient and the conductivity.

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“…Although it is known that e.g. the hole mobility in the donor phase may depend critically on the amount of acceptor material, 11,12 such aspects have received relatively little attention. While this may not pose any problem when describing a single OPV device, it can become problematic if one aims to evaluate a range of D:A compositions or several material combinations -if one uses quantitative predictions in search for the optimal device, the composition dependence of the mobility and/or the energetic disorder should be accounted for.…”

Section: Introductionmentioning

confidence: 99%

Design Rule for Improved Open-Circuit Voltage in Binary and Ternary Organic Solar Cells

Felekidis

Melianas

Kemerink

2017

ACS Appl. Mater. Interfaces

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Mixing different compounds to improve functionality is one of the pillars of the organic electronics field. Here, the degree to which the charge transport properties of the constituent materials are simply additive when materials are mixed is quantified. It is demonstrated that in bulk heterojunction organic solar cells, hole mobility in the donor phase depends critically on the choice of the acceptor material, which may alter the energetic disorder of the donor. The same holds for electron mobility and disorder in the acceptor. The associated mobility differences can exceed an order of magnitude compared to pristine materials. Quantifying these effects by a state-filling model for the open-circuit voltage (V) of ternary Donor:Acceptor1:Acceptor2 (D:A:A) organic solar cells leads to a physically transparent description of the surprising, nearly linear tunability of the V with the A:A weight ratio. It is predicted that in binary OPV systems, suitably chosen donor and acceptor materials can improve the device power conversion efficiency (PCE) by several percentage points, for example from 11 to 13.5% for a hypothetical state-of-the-art organic solar cell, highlighting the importance of this design rule.

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Impact of doping on the density of states and the mobility in organic semiconductors

Cited by 88 publications

References 32 publications

Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

Range and energetics of charge hopping in organic semiconductors

Design Rule for Improved Open-Circuit Voltage in Binary and Ternary Organic Solar Cells

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