ALBATROSS · Assembling Langmuir-Blodgett Architectures Through the use of Roll-to-roll Systems

Assembling Langmuir-Blodgett Architectures Through the use of Roll-to-roll Systems

The objective of the joint research programme was threefold – a) to develop a novel equipment by systematic modifications and improvements of an existing Langmuir-Blodgett dipper mechanism that has been in course of manufacture by one of the partners, b) to use it for deposition of colloidal nanoparticles (NP) with the aim of improving properties of solar cells and OLEDs that were being developed by the partners from Academia within the frame of nationally funded projects, and c) to provide opportunities for training and scientific exchanges for research personnel, including PhD students. The project was divided into 3 Work Packages. In WP1(the lead partner Tyndall ) the Belorussian SME Microtestmachines (MTM) developed 2 Roll-to-roll (R2R) dipper mechanisms, which were used for the deposition of colloidal photonic crystals on different substrates as well as for preparing heterocrystals made from the silica spheres of different diameters. The dipper prototypes are now located at Tyndall (Cork) and at STUBA (Bratislava). Both systems are fast, versatile, scalable and are being used for fabrication of high quality 2D and 3D photonic crystal (PhC) structures on flexible polyethylene terephthalate (PET) substrates. The system in Tyndall allows the preparation of samples with a total area up to 350 cm2. Recently, a simple thin film transfer process was developed in the Tyndall laboratories, which is compatible with R2R processing technologies and the colloidal photonic films produced can be transferred and applied onto real-size optoelectronic devices. WP2 (the lead partner STUBA) was aimed at OLED/OPV development. A typical OLED/OPV device consists of several organic layers situated between two electrodes whereas at least one of them is transparent. Tyndall provided STUBA with substrates comprising of different number of layers of NP PhCs that were used for organic device fabrications. OLED and OPV samples were prepared. In the case of OLEDs, the improvement of light extraction efficiency by 12% was achieved for 4 layer silica NP PhC, which shows the effect of the NP PhC use. In the case of OPVs, the maximum efficiency achieved (without PhCs) was 1.1%. By application of silica NPs, both current-voltage characteristics of the device and the energy conversion efficiency worsened. This was, however true only in the case of normal light incidence. When the light struck upon the cell at an angle, the conversion efficiency decrease was reduced if PhCs were applied. NPs having smaller sizes are more effective. This WP also dealt with modelling spectra of different PhC assemblies and materials research conducted by Tyndall and STUBA aimed at experimenting with new organic semiconductors and producing ITO-free devices. WP3 (the lead partner Powertec) covered Technology and diagnostics. By the end of the project, OPV demonstrators were produced both in Tyndall and in STUBA, using different active materials and different technologies. STUBA researchers used vacuum technologies available at their Organic Electronics laboratory and Pentacene – Fullerene as active materials. Tyndall researchers aimed at using the ALBATROSS specific R2R techniques, namely the R2R LB dipper mechanism (produced by MTM), a prototype of R2R device from IFSC University of Sao Paulo for depositing P3HT: PCBM and the ALD method to deposit a protective Al2O3 layer. The top electrodes, however had to be deposited by the TE method. The efficiencies of STUBA OPVs were about 1.1%, while the Tyndall ones deposited on flexible substrates were lower, in the range of 0.1-0.15%. This was due to degradation processes and the efficiencies can be increased by optimising technological processes. Such low values prevent, for the time being the commercial exploitation of these devices. We are, however certain that this is the right direction and continue our work under the SFI award “Design, Deposition and Exploitation of Novel Micro and Nano-scale Materials and Devices for Advanced Manufacturing – DEPO-Man” (2016-2020), in which the former members of the ALBATROSS consortium agreed to participate. (2-pages long Final publishable summary report, which includes the project logo and 3 figures is attached)

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