On the unipolarity of charge transport in methanofullerene diodes

Armin, Ardalan; Shoaee, Safa; Lin, Qianqian; Burn, Paul L.; Meredith, Paul

doi:10.1038/s41528-017-0012-y

Cited by 18 publications

(22 citation statements)

References 29 publications

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“…Interestingly, D18 exhibited prominent hole extraction but a negligible signal from the electron-based devices, indicating a typical unipolar charge transport property. 35 The calculated hole mobility is 1.2 × 10 −3 cm 2 V −1 s −1 , which is almost identical to the TRMC result.…”

Section: Resultssupporting

confidence: 80%

“…Panels e and f of Figure display the MIS-CELIV transient current of the hole and electron devices at offset voltages of 0 and 1 V, respectively. Interestingly, D18 exhibited prominent hole extraction but a negligible signal from the electron-based devices, indicating a typical unipolar charge transport property . The calculated hole mobility is 1.2 × 10 –3 cm 2 V –1 s –1 , which is almost identical to the TRMC result.…”

Section: Results and Discussionsupporting

confidence: 67%

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High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

et al. 2021

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Organic optoelectronics has progressed excitingly in recent years, mainly due to the innovation of donor and acceptor systems. Organic photodetectors based on novel semiconductor materials and well-designed device architectures have also been reported with improved device performance. However, most of them were photodiodes, and it is challenging to integrate them into the well-established readout circuits. Organic phototransistors are mainly based on the hybrid strategy, composed of either hybrid films or multilayer device structures, which complicates charge transfer and charge transport. Most of the organic devices also suffer from poor stability. In this work, we introduce a recently developed p-type copolymer, D18, to fabricate high-performance phototransistors. D18 possesses excellent charge generation, high mobility, and unipolar charge transport, which fulfill the generic design rule of organic phototransistors. The optimized phototransistors based on D18 exhibited extremely low dark current (∼10 pA) and noise (∼10 fA/Hz 1/2 ), a high detectivity of 4 × 10 13 Jones, a swift response of <5 ms, and excellent device stability. We also demonstrated flexible phototransistors with decent performance metrics, indicating great potential for next-generation solutionprocessed photodetectors and flexible electronic devices.

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Section: Resultssupporting

confidence: 80%

Section: Results and Discussionsupporting

confidence: 67%

High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

et al. 2021

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“…These traps define an energetic window for bipolar trap-free charge transport in organic semiconductors: if the lowest unoccupied molecular orbital (LUMO) [or highest occupied molecular orbital (HOMO)] lies above [below] the electron [hole] trap level, the electron [hole] transport is inevitably trap-limited. This explains the unipolarity of long-range charge transport in most organic semiconductors at low carrier densities 8,10 . However, we note that a different conclusion was reached in a recent study by Zuo et al who suggested that the traps are caused by water-filled nanovoids, inducing trap levels that are always~0.3-0.4 eV above (below) the HOMO (LUMO) 11 .…”

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confidence: 86%

Direct observation of trap-assisted recombination in organic photovoltaic devices

et al. 2021

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Trap-assisted recombination caused by localised sub-gap states is one of the most important first-order loss mechanism limiting the power-conversion efficiency of all solar cells. The presence and relevance of trap-assisted recombination in organic photovoltaic devices is still a matter of some considerable ambiguity and debate, hindering the field as it seeks to deliver ever higher efficiencies and ultimately a viable new solar photovoltaic technology. In this work, we show that trap-assisted recombination loss of photocurrent is universally present under operational conditions in a wide variety of organic solar cell materials including the new non-fullerene electron acceptor systems currently breaking all efficiency records. The trap-assisted recombination is found to be induced by states lying 0.35-0.6 eV below the transport edge, acting as deep trap states at light intensities equivalent to 1 sun. Apart from limiting the photocurrent, we show that the associated trap-assisted recombination via these comparatively deep traps is also responsible for ideality factors between 1 and 2, shedding further light on another open and important question as to the fundamental working principles of organic solar cells. Our results also provide insights for avoiding trap-induced losses in related indoor photovoltaic and photodetector applications.

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“…In a field-effect transistor at high gate bias, charge-carrier densities are high, which obscures the presence of bulk traps or tail states to a certain degree [19]. By contrast, at low carrier densities in a diode configuration, measurements of the bulk mobility in [60]PCBM and [70]PCBM showed highly unipolar transport, with hole mobilities more than 6 orders of magnitude lower than the electron mobilities [20], comparable to what has been observed for C 60 thin films [15][16][17]. It should be noted that for charge-transport characterization in a diode configuration Ohmic contacts are of critical importance.…”

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confidence: 99%

Trap-Free Space-Charge-Limited Hole Transport in a Fullerene Derivative

2019

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Fullerenes and their derivatives are well-known electron-transporting materials used in organic solar cells and transistors. However, the extent to which fullerenes are able to transport holes is heavily disputed. Using selective Ohmic contacts, we study the bulk hole and electron transport in a bisadduct fullerene derivative. Trap-free space-charge-limited hole and electron currents are measured, with a hole mobility equivalent to the electron mobility. Our results identify the bisadduct fullerene as an organic semiconductor with balanced bipolar bulk transport with excellent electron and hole mobilities.

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On the unipolarity of charge transport in methanofullerene diodes

Cited by 18 publications

References 29 publications

High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

High-Performance Organic Phototransistors Based on D18, a High-Mobility and Unipolar Polymer

Direct observation of trap-assisted recombination in organic photovoltaic devices

Trap-Free Space-Charge-Limited Hole Transport in a Fullerene Derivative

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