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: “7^th European Congress on Advanced Nanotechnology and Nanomaterials Webinar” November 14^th- 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. Petre^1,3,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 Africa^3, 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 Petre^1,3, 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