Flexible and nanostructured Organic Field Effect Transistor for UV-VIS detection

Project Director: Dr. Anca STANCULESCU

 Project Cod: , PN-III-P2-2.1-PED-2021-3165 

Project Director : Dr. Anca Stanculescu

Project type: National

Program: Program 2: P2 - Increasing the competitiveness of the Romanian economy through CDI; Subprogram Competitiveness through research, development and innovation (partially); Experimental Demonstration Project (PED)

Founded by: The Executive Agency for Higher Education, Research, Development and Innovation Funding(UEFISCDI)

Contractor: National Institute of  Materials Physics

Status: In development

Start date: 30.06.2022

End date: 30.06.2024


The organic phototransistors (OPTs) are optical transducer based on organic field effect transistors (OFETs) showing good absorption in a specific domain and high efficiency of photocurrent generation, with many applications in industrial, military, environmental and biological sectors.

The project is focused on obtaining OFET structures on flexible substrate with improved properties, sensitive to UV-VIS illumination, avoiding the use of expensive and limited resources raw materials (indium).

In the frame of this project will be developed original ideas concerning: the active layer  for OFET from oligomers/polymers based on arylaminic derivatives;  transistor  channel type bulk heterojunction (BHJ), mixed layer from the mentioned donors and a non-fullerene perylene diimide derivative acceptor; transparent gate electrode indium-free made from Al doped ZnO ; modification of the surfaces/interfaces by nanostructuring.

For an increase from TRL 2 (concept of OFET sensible to UV-VIS radiation) to TRL 3 (experimental demonstrator of a flexible, ambipolar OFET with reproducible electrical parameters in dark and response under illumination) are proposed the following objectives: 1. Preparation of active layer from new organic compounds and transparent gate electrode for OFET structures. 2. Realization of new nanostructured OFET structures sensible to UV-VIS radiation

The project feasibility is sustained by the preliminary experimental results and expertise concerning the synthesis of the compounds (PPIMC/P1), transparent conductor electrodes (INFLPR/P2), organic thin film (CO+P2) and nanostructuring (CO), research strategy and infrastructure of the partners. CO will be in charge with the realization of the OFETs and their characterization in dark and at illumination, P1 with the synythesis, purification and characterization of the compounds for channel material and P2 with the deposition of transparent conductor electrode and of the mixed layer (BHJ).

National Institute of Materials Physics (NIMP) -CO

Dr. Anca Stanculescu-Project Director

Dr. Nicoleta Preda-scientific researcher  1

Dr. Marcela Socol-Scientific researcher 1

Dr. Oana Rasoga-Scientific researcher  2

Dr. Carmen Breazu-Scientific researcher 3

Dr. Paul Ganea-scientific researcher  3

Gabriela Petre -PhD student

"P. Poni" Institute of Macromolecular Chemistry (PPIMC)-P1

Dr. Andrei Honciuc-Partner Responsible

Dr. Ana-Maria Solonaru-Scientific researcher

Dr. Oana-Iulia Negru-Research assistant

National Institute for Laser, Plasma and Radiation physics (NILPRP)-P2

Dr. Gabriel Socol- Partner Responsible

Dr. Gianina Popescu-Pelin-Scientific researcher 3

Andreea Mihailescu-Research assistant, PhD student

Andrei Stochioiu-PhD student

Ion Tudor-technician

Stage 1: Preparation of channel active layer from new organic compounds and transparent gate electrode for OFET structures

In the frame of this stage we have synthetized and preliminary characterized organic compounds (donors and acceptors) which will be utilized in the next stages for the preparation of the channel active material in organic field effect transistor (OFET) structure.  Perylene diimides have been proposed as acceptors because of their high electrons affinity, high light absorption coefficient and good transport properties. By functionalization, in different positions, with alkyl or aryl group to the nitrogen atoms, the solubility in common solvents is improved, the segregation is prevented and the preparation of high quality thin films adequate for electronic applications (OFETs), is favored. Good absorption in visible domain and a position of the HOMO and LUMO levels favoring the charge transport which is not trap-limited, have been revealed for the selected acceptor compound that contains the alkyl substituent group.  Two arylenvinylene based monomers and intermediary monomers for the preparation of polymers with arylenvinylene and arylenethynilene structure containing 2,7-dibrom N-(2-ethyl-hexyl) were also synthetized. These compounds, showing extended absorption and good transport of the carriers, will be used as donors.

Transparent conducting oxide/TCO layers (Al:ZnO/AZO; In:ZnO/IZO90) were deposited by PLD on different flexible substrates: PES 0.25 mm, PES 0.5 mm, PET amorphous; PET biaxial oriented and flexible glass. Correlating  the morphological properties (uniform deposition) with those of transmission (>90 %) and sheet resistance (~5x102 ohm/□), the PES 0.5 mm and PES 0.25 mm substrates  can be selected for the deposition of the AZO and IZO90 transparent conductor layer.

Uni-component (donor, acceptor) and mixed donor (arylenvinylene monomer):acceptor (perylene diimide derivative) layers were prepared on the mentioned substrates using the vacuum evaporation and deposition technique. FTIR analysis has confirmed the deposition of mixed layers containing the both components and the preservation of the chemical structure of the donor and acceptor, during the deposition process. The optical analysis has revealed that, in principle, all types of substrate can be utilized for the deposition of the organic films which show absorption bands both in UV and Vis, with the exception of PES 0.25 mm which cut the signal for wavelengths <400 nm. Considering the losses by radiative relaxation mechanisms, PET amorphous, PET biaxially oriented and flexible glass have resulted as the most appropriate substrates for the deposition of simple and mixed organic layers from the selected compounds for Vis applications and flexible glass for UV applications. Correlating the transmission and photoluminescence results, the PES 0,25 mm substrate can not be used in UV domain. Taking into account, both the morphology of the layer (low roughness can reduce the scattering) and the optical properties, flexible glass is a good option of substrate for the deposition of mixed organic layers. The dielectric properties of the organic layer are not significantly affected by the type of substrate and thus they don’t have a critical role in the selection of the substrate. Considering the electrical properties of the TCO and organic layer, PES 0.5 mm and PES 0.25 mm are the most appropriate substrates for deposition. Therefore, choosing the substrate for the realization of the heterostructure it is a process that requires the consideration of several factors such as: type and properties of the TCO layer, composition and properties of the mixed layer. The substrate covered by the transparent conductor (the gate in OFET structure) must be transparent in UV and/or Vis and the organic layer must absorb the UV and/or Vis radiation that will be involved in the generation of charge carriers.

In conclusion, the objectives of this stage have been achieved: donors and acceptor compounds have been synthetized and characterized, transparent conductor layers and organic layers have been deposited on flexible substrates. The layers were characterized from morphologic, optic, electric, dielectric point of view, in order to be selected in correlation with the type of substrate. The heterostructure with mixed organic layer (monomer based on arylenvinylene):acceptor (perylendiimide) deposited on flexible AZO showed the best transport properties.


1 paper communicated at: “7th European Congress on Advanced Nanotechnology and Nanomaterials WebinarNovember 14th- 15th, 2022, Rome, Italy.

Title: "Organic heterostructure with dendrimer:non-fullerene mixed layer for electronic applications"

Authors: C. Breazu1, A. Lutgarde Djoumessi Yonkeu2, O. Rasoga1, M. Socol1, N. Preda1, G. Petre1,3,F. Stanculescu3, A. Stanculescu1, E. Iwouha2

1National Institute of Materials Physics, Atomistilor 405A, 077125, Magurele, Romania, 2University of Western Cape, Department of Chemistry, SensoLab, Robert Sobukwe Road, P. Bag X17, Bellville 7535, Cape Town, South Africa3, University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Bucharest-Magurele, 077125 Romania, 4Laboratoire LPHIA, Université d’Angers, LUNAM 2, Bd. Lavoisier 49045, Angers, France


1 paper accepted for publication in Nanomaterials

Title: "Effect of Aluminum nanostructured electrode on the properties of bulk heterojunctions based heterostructures for electronics"

Authors: Oana Rasoga1, Carmen Breazu1, Marcela Socol1, Ana-Maria Solonaru2, Loredana Vacareanu2, Gabriela Petre1,3, Nicoleta Preda1, Florin Stanculescu3, Gabriel Socol4, Mihaela Girtan5, Anca Stanculescu1

1National Institute of Materials Physics, 405A Atomistilor Street, P.O. Box MG-7Magurele, 077125 Romania; 2P. Poni Institute of Macromolecular Chemistry, 41 A Gr. Ghica Voda Alley, 700487, Iasi, Romania; 3University of Bucharest, Faculty of Physics, 405 Atomistilor Street, P.O. Box MG-11, Magurele, 077125 Romania; 44National Institute for Laser, Plasma and Radiation Physics, Str. Atomistilor, Nr. 409, PO Box MG-36, Bucharest, 077125, Romania; 5Laboratoire LPHIA, Université d’Angers, LUNAM, 2 Bd. Lavoisier 49045, Angers, France


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