Tiziano Agostinelli

Endomag (United Kingdom)

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Jenny Nelson

Imperial College London

M. Sampietro

Politecnico di Milano

Dario Natali

Politecnico di Milano

Samuele Lilliu

University of Sheffield

Mariano Campoy‐Quiles

Institut de Ciència de Materials de Barcelona

Donal D. C. Bradley

University of Oxford

J. Emyr Macdonald

Cardiff University

Mario Caironi

Center for Nano Science and Technology

Ellis Pires

Cardiff University

Mark Hampton

Cardiff University

Cooperative Institutions

Imperial College London

Politecnico di Milano

University of Oxford

University of Cambridge

Mylan (South Africa)

Mylan (Switzerland)

University of Cagliari

Italian Institute of Technology

Center for Nano Science and Technology

National Interuniversity Consortium of Materials Science and Technology

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Visible and infrared light pulse detection with organic semiconductors

Tiziano Agostinelli Massimiliano Arca Mario Caironi F.A. Devillanova Valter Ferrero

Visible spectrum

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Citations (0)

Morphology evolution via self-organization and lateral and vertical diffusion in polymer:fullerene solar cell blends

Nature Materials (2008)

Mariano Campoy‐Quiles Toby A. M. Ferenczi Tiziano Agostinelli P. Etchegoin Youngkyoo Kim

Thermal Treatment

Morphology

10.1038/nmat2102

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Citations (1,434)

Field-Independent Charge Photogeneration in PCPDTBT/PC₇₀BM Solar Cells

The Journal of Physical Chemistry Letters (2010)

Fiona C. Jamieson Tiziano Agostinelli Hamed Azimi Jenny Nelson James R. Durrant

Transient absorption spectroscopy has been used to investigate charge photogeneration in organic solar cells based upon PCPDTBT/PC70BM (poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)]/[6,6]-phenyl-C71-butyric acid methyl ester) photoactive layers as a function of externally applied bias. We find that the yield of dissociated polarons is independent of applied bias in these devices.

10.1021/jz1013517

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Citations (91)

The Influence of Substrate and Top Electrode on the Crystallization Dynamics of P3HT: PCBM Blends

Energy Procedia (2012)

Samuele Lilliu Tiziano Agostinelli Mark Hampton Ellis Pires Jenny Nelson

Substrate and top electrode effects on P3HT lamellar crystallization, were studied using the full device structure of a bulk-hetorojunction P3HT:PCBM organic solar cell, during thermal annealing. P3HT: PCBM chlorobenzene solutions (50 wt %) were spin coated on quartz, HMDS treated SiO2, SiO2/PEDOT: PSS, ITO/PEDOT: PSS. The structural evolution of these thick (∼100nm) films was probed during a realistic device-processing annealing cycle at 140°C for ∼53 minutes by time-resolved synchrotron Grazing Incidence X-Ray Diffraction (GI-XRD). The 20 nm- thick coated Aluminium layer on top of ITO/PEDOT: PSS/P3HT: PCBM acts as a nucleation site for the P3HT crystalline growth during annealing, increasing the number of the edge-on lamellae, and preferentially increasing the domain size of face on and edge-on lamellae, with minor growth of the randomly oriented lamellae.

10.1016/j.egypro.2012.11.165

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Citations (9)

A heteroquaterphenoquinone-based blend for near infrared photodetectors: device performance and study of the photoexcitation dynamics

Eleonora V. Canesi Tiziano Agostinelli J. Cabanillas-Gonzales Mario Caironi Giovanni Dassa

Photoexcitation

Dynamics

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X-ray stability and response of polymeric photodiodes for imaging applications

Applied Physics Letters (2008)

Panagiotis E. Keivanidis Neil C. Greenham Henning Sirringhaus Richard H. Friend James C. Blakesley

The x-ray stability of photodiodes made of poly(9,9-di-n-octylfluorene-co-benzothiadiazole):perylene diimide, poly[2,7-(9,9-di-n-octylfluorene)-co-(1,4-phenylene-[(4-sec-butylphenyl)imino]-1,4-phenylene)]:perylene diimide and poly(3-hexylthiophene):([6,6]-phenylC61-butyric acid methyl ester) (P3HT:PCBM) blends has been examined up to lifetime doses equivalent to those used in medical x-ray digital imaging applications. Dark currents and external quantum efficiencies (EQEs) are not significantly affected after exposure to 500Gy. Only in the case of P3HT:PCBM is a significant loss in EQE (17% of the initial value) observed. Possible reasons for the observed changes are proposed. When a scintillation layer is attached to the devices, a linear dependence of the photocurrent on the x-ray dose rate is observed for the three material systems.

Diimide

Photocurrent

Photodiode

Quantum Efficiency

Organic semiconductor

10.1063/1.2834364

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Citations (66)

Space charge effects on the active region of a planar organic photodetector

Journal of Applied Physics (2007)

Tiziano Agostinelli Mario Caironi Dario Natali M. Sampietro P. Biagioni

Planar organic photodetectors represent a simple, cheap, and versatile alternative to devices built in sandwich configuration. The nonuniform electric field distribution in these structures has significant consequences on the extent of the device active region, because photogeneration of free carriers in organic semiconductors is a field-assisted phenomenon. By means of microscopy mapping of the photocurrent in a poly(p-phenylene vinylene) based planar device, we show that due to the deep trapping of photogenerated electrons leading to negative space charge accumulation, exciton dissociation occurs only close to the positively biased electrode. The effect of large leakage currents in defining the device active region is also analyzed and discussed.

Photocurrent

Organic semiconductor

Charge carrier

Photoconductivity

10.1063/1.2738429

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Citations (34)

Real‐Time Investigation of Crystallization and Phase‐Segregation Dynamics in P3HT:PCBM Solar Cells During Thermal Annealing

Advanced Functional Materials (2011)

Tiziano Agostinelli Samuele Lilliu John G. Labram Mariano Campoy‐Quiles Mark Hampton

Abstract Crystallization and phase segregation during thermal annealing lead to the increase of power‐conversion efficiency in poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl C61‐butyric acid methyl ester (PCBM) bulk‐heterojunction solar cells. An understanding of the length and time scale on which crystallization and phase segregation occur is important to improve control of the nanomorphology. Crystallization is monitored by means of grazing incidence X‐ray diffraction in real time during thermal annealing. Furthermore, the change in film density is monitored by means of ellipsometry and the evolution of carrier mobilities by means of field effect transistors, both during annealing. From the combination of such measurements with those of device performance as a function of annealing time, it is concluded that the evolution of microstructure involves two important time windows: i) A first one of about 5 minutes duration wherein crystallization of the polymer correlates with a major increase of photocurrent; ii) a second window of about 30 minutes during which the aggregation of PCBM continues, accompanied by an increase in the fill factor.

Photocurrent

10.1002/adfm.201002076

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Citations (213)

A planar organic near infrared light detector based on bulk heterojunction of a heteroquaterphenoquinone and poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1, 4-phenylene vinylene]

Journal of Applied Physics (2008)

Tiziano Agostinelli Mario Caironi Dario Natali M. Sampietro Giovanni Dassa

Planar organic detectors for the near infrared region of the light spectrum have been realized, processing from solution the quinoid molecule 5,5′-bis(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)-5,5′-dihydro-2,2′-bithiophene (QBT), which shows a peculiar absorption at 680 nm. Sensitization of the active material was obtained by creating a bulk donor-acceptor interface with poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene], which acts as hole acceptor. Photoexcitation and relaxation dynamics in pristine materials and bulk heterojunction have been investigated by means of pump-probe measurements, revealing charge transfer from QBT to polymer and efficient energy transfer the other way round.

Photoexcitation

Acceptor

Photoconductivity

10.1063/1.3033376

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Citations (27)

Influence of Bridging Atom and Side Chains on the Structure and Crystallinity of Cyclopentadithiophene–Benzothiadiazole Polymers

Chemistry of Materials (2013)

Anne A. Y. Guilbert Jarvist M. Frost Tiziano Agostinelli Ellis Pires Samuele Lilliu

We use grazing-incidence wide-angle X-ray scattering (GIWAXS) and molecular modeling to understand the difference in crystallization of several cyclopentadithiophene–benzothiadiazole polymer derivatives. We observe using GIWAXS that when the carbon bridging atom is substituted by a silicon atom, the π–π stacking distance is decreased while the lamellar stacking distance is increased. Using molecular modeling, we calculate the potential energy surfaces of an ordered array of oligomers as a function of π–π stacking and lamellar stacking distances and find two local minima for both the carbon and silicon analogues. This finding is consistent with the GIWAXS observations. We suggest that it may be possible to crystallize the carbon and silicon versions in the same crystal structure by varying the processing conditions. We derive new potential parameters from quantum chemical calculations for side chains motions and implement those within a new force field for molecular dynamics. We find that the side chains are more flexible in the case of the silicon bridging atom. We propose that the flexibility enhancement may influence both thermodynamics and kinetics of crystallization and may result in crystallization of the polymer in the first or the second energetically favored crystal structures. This interpretation is supported by the finding of only one minimum in potential energy for longer, less bulky, and, thus, more flexible side chains for the carbon analogue.

Side chain

10.1021/cm403410w

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Citations (51)