Density of trap states in organic photovoltaic materials from LESR studies of carrier recombination kinetics

Carati, Claudio; Bonoldi, Lucia; Pò, Riccardo

doi:10.1103/physrevb.84.245205

Cited by 16 publications

(24 citation statements)

References 37 publications

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“…One approach that is applicable to thin films of π‐conjugated polymers is based upon electron spin resonance (ESR) spectroscopy, using either electric‐field‐injected charge carriers (field‐induced ESR: FI‐ESR or FESR) or photoexcited carriers (light‐induced ESR: LESR) …”

Section: Introductionmentioning

confidence: 99%

Electrically Detected Magnetic Resonance Observations of Spin‐Dependent Space‐Charge‐Limited Conduction in Regioregular Poly(3‐Hexylthiophene)

Fukuda

Asakawa

2017

Macro Chemistry & Physics

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Pauli spin blockade associated with bipolaron formation from positively charged mobile and trapped polarons in a regioregular poly(3‐hexylthiophene‐2,5‐diyl) (RR‐P3HT) Schottky barrier diode is detected using electrically detected magnetic resonance (EDMR) spectroscopy. This is the first experimental observation of bipolaron formation from positively charged mobile and trapped polarons in the space‐charge‐limited conduction regime in a polymer semiconductor. It is inferred that carrier traps exist in the disordered regions at the crystalline grain boundaries in RR‐P3HT. Furthermore, EDMR measurements under various constant‐current conditions suggest that shallow and deep traps have distinguishable g‐values.

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Section: Introductionmentioning

confidence: 99%

Electrically Detected Magnetic Resonance Observations of Spin‐Dependent Space‐Charge‐Limited Conduction in Regioregular Poly(3‐Hexylthiophene)

Fukuda

Asakawa

2017

Macro Chemistry & Physics

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“…[50] The moving charge may be confined to these trap states for a time interval that may depend upon the trap depth and temperature of the system. [50] These trap states were described as either mid-gap states or the shallow tail states lying below the transport gap. [51][52][53] Trap states were shown to have important consequences on the charge carrier dynamics of OPV devices.…”

Section: Role Of Trap-states In Opd Performance Metricsmentioning

confidence: 99%

“…In organic BHJ, the separated charges moving through percolating paths toward the respective electrodes may interfere distributed “defective or impurity sites” of lower energy, called trap states. [ 50 ] The moving charge may be confined to these trap states for a time interval that may depend upon the trap depth and temperature of the system. [ 50 ] These trap states were described as either mid‐gap states or the shallow tail states lying below the transport gap.…”

Section: Role Of Trap‐states In Opd Performance Metricsmentioning

confidence: 99%

Progress in Organic Photodiodes through Physical Process Insights

Chandran

Yan

2022

Adv Energy and Sustain Res

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Photodetectors are vital components in applications like health monitoring, [1] optical communication, [2] night vision, [3] surveillance, [4] motion detection, [5] collision avoidance systems for autonomous vehicles, etc. [6,7] Due to their mature fabrication technology, appreciable performance, robust stability, and high-level integration with existing electronics, crystalline inorganic semiconductors-based photodetectors remain the choice of photodetection technology. [8,9] However, these inorganic photodetectors (IPDs) are facing challenges in fitting into the new age flexible/ wearable devices due to their rigid/brittle nature. [10] The expensive and complicated manufacturing of IPD is also causing issues in realizing low-cost mass production. Being broadband absorbers, the use of color filters is a prerequisite in IPD for narrowband sensing. [11][12][13] Integration of color filters further complicates the device architecture and negatively affects pure color replication. Thus, scientific communities are in search of potential IPD alternatives that offer low-cost fabrication, high performance, stability, and favorable mechanical properties.Solution-processed photodetectors are potential alternatives to IPDs, primarily due to low-cost fabrication and attractive mechanical properties. [14][15][16] Photodetectors that can adhere to flexible, curved, and soft surfaces are in high demand due to their applications in human-activity monitoring and personal health care. [17][18][19] Organic photodetectors are the front runners in this segment and offer enormous advantages like tunable optoelectronic properties, [20] low-temperature/low-cost processing, [21] flexibility, [19] lightweight, [22] and biocompatibility. [23] Two terminal organic PDs have either photoconductor or photodiode architecture. [20] For photoconductors, organic semiconductor is sandwiched between two symmetrical contacts. Due to the carrier recirculation through symmetrical contacts, this device structure allows photoconductive gain >100%. [20] Photomultiplier (PM)-type organic photodetector with charge tunneling injection is also capable of producing gain. Recent efforts have realized novel broadband/narrowband PM-type organic photodetectors with an external quantum efficiency (EQE) values much higher than 100%. [24][25][26][27][28][29] However, as a result of carrier trapping, the response speed of PM organic photodetectors is relatively slow. [20] Depending upon the application, a compromise between gain and response speed is indeed needed. [30] The most common type of organic photodetector is an organic photodiode (OPD). A photodiode has a simple architecture in which an active layer is sandwiched between transparent and metal electrodes. [6,20,31] The structure and working principle are more like organic solar cells. [6] Though the photodiodes do not produce any gain effect, they exhibit low dark current density ( J d ), fast temporal response, and broad linear dynamic (LDR) range. [6] Intense research efforts in the past few years have tra...

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“…The consequences of PyBB addition were spectroscopically investigated by means of light-induced electron paramagnetic resonance (LEPR) and emission fluorescence spectroscopy. The density of trap states in two- and three-components blends was calculated according to a previously published method, and the electrical properties of the devices made of PTB7:C 60 or PTB7:C 70 blends prepared with or without PyBB were evaluated. Both the spectroscopic and the electrical investigation indicated that PyBB addition has important consequences on the morphology of the blends as well as on their charge transport properties.…”

Section: Introductionmentioning

confidence: 99%

Pyrene–Fullerene Interaction and Its Effect on the Behavior of Photovoltaic Blends

Carati

Gasparini

Righi³

et al. 2016

J. Phys. Chem. C

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Improving the dispersion properties of unfunctionalized fullerenes in photovoltaic blends is a key factor for replacing the commonly employed butyric acid methyl ester derivatives (PBCM and PC 71 BM), with economical and light harvesting advantages. We consider here the effects of a pyrene derivative (PyBB) as dispersant of neat fullerenes (C 60 or C 70 ) in photovoltaic blends prepared with a low energy gap conjugated polymer (PTB7) as electron donor. The morphological and spectroscopic properties in the presence and absence of PyBB were evaluated by AFM, emission fluorescence, and light induced EPR, and the deep trap density of states was calculated in the two cases. The electrical properties of the devices prepared with or without PyBB were investigated and compared. The intimate interaction of fullerene/PyBB aromatic species revealed by the spectroscopic analysis is in agreement with the enhanced dispersion of the three-component blends. At the same time the deep trap density of states is varied, and the mobility of negative charge carriers is reduced in films prepared with PyBB dispersant, frustrating the beneficial effect of PyBB on the blend morphology.

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Density of trap states in organic photovoltaic materials from LESR studies of carrier recombination kinetics

Cited by 16 publications

References 37 publications

Electrically Detected Magnetic Resonance Observations of Spin‐Dependent Space‐Charge‐Limited Conduction in Regioregular Poly(3‐Hexylthiophene)

Electrically Detected Magnetic Resonance Observations of Spin‐Dependent Space‐Charge‐Limited Conduction in Regioregular Poly(3‐Hexylthiophene)

Progress in Organic Photodiodes through Physical Process Insights

Pyrene–Fullerene Interaction and Its Effect on the Behavior of Photovoltaic Blends

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