On the validity of MIS-CELIV for mobility determination in organic thin-film devices

Sandberg, Oskar J.; Nyman, Mathias; Dahlström, Staffan; Sandén, Simon; Törngren, Björn; Smått, Jan‐Henrik; Österbacka, Ronald

doi:10.1063/1.4980101

Cited by 39 publications

(32 citation statements)

References 18 publications

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“…Charge carrier mobilities were determined using Resistance‐dependent photovoltage (RPV), [ 29 ] metal–insulator–metal charge extraction by a linearly increasing voltage (MIM‐CELIV) [ 30,31 ] and metal–insulator–semiconductor charge extraction by a linearly increasing voltage (MIS‐CELIV). [ 32,33 ] RPV and MIM‐CELIV were carried out on PM6:Y6 solar cells with inverted device structures (glass/ITO/ZnO/active layer/MoO 3 /Ag). RPV can be used to selectively measure the mobility of the two different photogenerated charge carrier types provided that the mobilities are sufficiently imbalanced, whereas MIM‐CELIV measures the mobility of the more conductive charge carrier.…”

Section: Resultsmentioning

confidence: 99%

Requirements for Making Thick Junctions of Organic Solar Cells based on Nonfullerene Acceptors

Nyman

Sandberg

et al. 2021

Solar RRL

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Organic bulk‐heterojunction solar cells based on the newly developed nonfullerene electron acceptors have the potential for very low‐cost energy production. However, to enable large‐scale production with common printing techniques, the active layer thicknesses need to be increased by up to an order of magnitude, which is currently not possible without significant loss in performance. Herein, the requirements for making nonfullerene acceptor (NFA)‐based solar cells with thick active layers and high efficiencies are clarified. The charge carrier mobility, unintentional doping concentrations, and bimolecular recombination prefactor in the model high‐efficiency system PM6 (Poly[(2,6‐(4,8‐bis(5‐(2‐ethylhexyl‐3‐fluoro)thiophen‐2‐yl)‐benzo[1,2‐b:4,5‐b′]dithiophene))‐alt‐(5,5‐(1′,3′‐di‐2‐thienyl‐5′,7′‐bis(2‐ethylhexyl)benzo[1′,2′‐c:4′,5′‐c′]dithiophene‐4,8‐dione)]):Y6 (2,2′‐((2Z,2′Z)‐((12,13‐bis(2‐ethylhexyl)‐3,9‐diundecyl‐12,13‐dihydro‐[1,2,5]thiadiazolo[3,4‐e]thieno[2″,3″:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2‐g]thieno[2′,3′:4,5]thieno[3,2‐b]indole‐2,10‐diyl)bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile) are determined. The results are implemented in a combined electro‐optical device model, which is used to determine the effect of varying these parameters on the efficiency. The results show that a mobility imbalance and doping can lead to improved performance at large thicknesses, partially contradicting previous studies performed on fullerene‐based systems. The findings highlight the importance of determining electron and hole mobilities selectively, as well as characterizing recombination and doping concentrations.

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Section: Resultsmentioning

confidence: 99%

Requirements for Making Thick Junctions of Organic Solar Cells based on Nonfullerene Acceptors

Nyman

Sandberg

et al. 2021

Solar RRL

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“…A small charge extraction regime of the MIS-CELIV experiment was used and a typical signal of the transient current is shown in Figure S2. In this regime, the condition Δ j ≤ j ( 0 ) is fulfilled and the monopolar charge carriers are extracted as a uniform sheet of charge [40]. The corresponding small-charge transit time t max for the sheet of carriers to reach the extracting contact defines the mobility as following: μ=2ds2Atmax21+f,where the ratio between the geometric capacitances of the PPQ–DBT semiconductor and the SiO 2 insulator layers f ≡ ( ε s d i )/( ε i d s ) is equal to ~0.3 since dielectric constant is ε i = 3.9 and ε s ≈ 2.5 for SiO 2 and PPQ–DBT, respectively.…”

Section: Methodsmentioning

confidence: 99%

Conductivity and Density of States of New Polyphenylquinoline

et al. 2019

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Electrical, photoelectrical, and optical properties of thin films of a new heat-resistant polyphenylquinoline synthesized using facile methods were investigated. An analysis of the obtained temperature dependences of the dark conductivity and photoconductivity indicates the hopping mechanism of conductivity over localized states arranging at the energy distance of 0.8 eV from the Fermi level located inside the band gap of the investigated material. The optical band gap of the studied material was estimated from an analysis of the spectral dependences of the photoconductivity and absorption coefficient before (1.8–1.9 eV) and after (2.0–2.2 eV) annealing at temperatures exceeding 100 °C. The Gaussian character of the distribution of the localized states of density inside the band gap near the edges of the bands was established. A mechanism of changes in the optical band gap of the investigating polymer under its annealing is proposed.

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“…Although it is well established that CELIV extracts carrier mobilities, different pitfalls for determining the exact value are known [12,22]. To gain another view on the change in charge-carrier mobility due to dipolar doping, TOF measurements are conducted on four different samples with doping ratios again ranging from 0% to 10%.…”

Section: B Bilayer Mis Structuresmentioning

confidence: 99%

Dipolar Doping of Organic Semiconductors to Enhance Carrier Injection

et al. 2019

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If not oriented perfectly isotropically, the strong dipole moment of polar organic semiconductor materials such as tris-(8-hydroxyquinolate)aluminum (Alq 3) will lead to the buildup of a giant surface potential (GSP) and thus to a macroscopic dielectric polarization of the organic film. Despite this having been a known fact for years, the implications of such high potentials within an organic layer stack have only been studied recently. In this work, the influence of the GSP on hole injection into organic layers is investigated. Therefore, we apply a concept called dipolar doping to devices consisting of the prototypical organic materials N ,N-Di(1-naphthyl)-N ,N-diphenyl-(1,1-biphenyl)-4,4-diamine (NPB) as nonpolar host and Alq 3 as dipolar dopant with different mixing ratios to tune the GSP. The mixtures are investigated in single-layer monopolar devices as well as bilayer metal/insulator/semiconductor structures. Characterization is done electrically using current-voltage (I-V) characteristics, impedance spectroscopy, and charge extraction by linearly increasing voltage and time of flight, as well as with ultraviolet photoelectron spectroscopy. We find a maximum in device performance for moderate to low doping concentrations of the polar species in the host. The observed behavior can be described on the basis of the Schottky effect for image-force barrier lowering, if the changes in the interface dipole, the carrier mobility, and the GSP induced by dipolar doping are taken into account.

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On the validity of MIS-CELIV for mobility determination in organic thin-film devices

Cited by 39 publications

References 18 publications

Requirements for Making Thick Junctions of Organic Solar Cells based on Nonfullerene Acceptors

Requirements for Making Thick Junctions of Organic Solar Cells based on Nonfullerene Acceptors

Conductivity and Density of States of New Polyphenylquinoline

Dipolar Doping of Organic Semiconductors to Enhance Carrier Injection

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