The Stratakis Lab

The Stratakis Lab

Ultrafast Laser Micro and Nano Processing Laboratory

Ultrafast Laser Synthesis of Nanomaterials

Ultrafast laser processing is a promising tool for the fabrication of nanomaterial of different morphologies for multiple applications ranging from diagnosis and imaging to solar cells. According these lines, two-dimensional structures (graphene-based) or other low dimensional nanosystems (fullerene-like MoS2 nanoparticles, WS2 nanotubes, perovskites of chemical nature type CsPbX3, where X: Cl, Br, I). In more details:


2D graphene-based structures:

Photochemical techniques have been introduced for the fabrication and modification of graphene-based materials for the enhancement of the photovoltaic devices’ performance. These materials can be used in organic electronics, particular to organic photovoltaics, field effect transistors and electron emission cathodes. In particular, a reduction technique using a femtosecond laser compatible with flexible, temperature sensitive substrates, have been utilized for the production of transparent conductive flexible graphene electrodes. These GO sheets can be further improved with a simultaneous reduction and doping with Cl or N through pulsed UV irradiation in liquid or gas media. Furthermore, a laser-based patterning technique has been developed for the production of large area reduced graphene oxide micromesh (rGOMM) electrodes for advanced photovoltaics.
Laser-induced techniques in colloidal medium have been also used to decorate the 2D materials with metallic or semiconducting nanoparticles (NPs). The second material has been synthesized with laser ablation techniques or colloidal wet chemistry methods. The hybrid systems have been designed in order to exploit both the contribution of NPs in the light absorption enhancement and the band gap tunability of the 2D materials. This could lead to higher exciton dissociation and charge collection in photovoltaic devices. It has been shown that few seconds of UV irradiation is sufficient to decorate the nanosheets lattice with NPs, while the nanoparticles density can be readily controlled upon variation of the irradiation time.


Low-dimensional materials:

Laser-ablation techniques with ultrashort pulses have been employed for the fabrication of fullerene-like MoS2 NPs as well as of WS2 nanotubes. The suggested method is simple and cost efficient as no high cost vacuum facilities are required. These findings open up great opportunities for the synthesis and study of new kinds of inorganic nanostructures with properties that may differ significantly from the corresponding bulk materials. Various potential applications ranging from catalysis and electronics to solar cells and drug delivery have been proposed for these low dimensional materials as they exhibit excellent solid lubrication behaviour.


Prof. Emmanuel Kymakis, Department of Electrical Engineering, Technical Educational Institute (T.E.I) of Crete
Prof. Constantinos Petridis, Department of Electronic Engineering, School of Applied Sciences, Technological Educational Institute of Crete
Prof. Thomas D. Anthopoulos Department of Physics & Centre for Plastic Electronics, Imperial College London, Blackett Laboratory
Dr. Antonios G. Kanaras, Physics & Astronomy, University of Southampton
Prof. Reshef Tenne, Weizmann Institute of Science, Israel



Solution-Processed Reduced Graphene Oxide Electrodes for Organic Photovoltaics
Petridis C., Konios D., Stylianakis M.M., Kakavelakis G., Sygletou M., Savva K., Tzourbakis P., Krassas M.,Vaenas N., Stratakis E., Kymakis E., Nanoscale Horizons, 1, 375-382, 2016

Laser induced  nucleation of  plasmonic nanoparticles on two-dimensional  nanosheets for organic photovoltaics
Sygletou M., Tzourmpakis P., Petridis C., Konios D., Fotakis C., Kymakis E., Stratakis E., Journal of Materials Chemistry A, 4, 1020-1027, 2016

High efficient organic photovoltaic devices utilizing work-function tuned graphene oxide derivatives as the anode and cathode charge extraction layer
Konios D., Kakavelakis G., Petridis C., Stratakis E., Kymakis E. Journal of Materials Chemistry A, 4, 1612-1623, 2016

Reduced graphene oxide micromesh electrodes for large area, flexible organic photovoltaic devices
Konios D., Petridis C., Kakavelakis G., Sygletou M., Savva K., Stratakis E., Kymakis E., Advanced Functional Materials, 25, 15, 2213-2221, 2015 [Appeared in the inside front cover of Adv. Funct. Mater]

Photochemical Synthesis of Solution-Processable Graphene Derivatives with Tunable Bandgaps for Organic Solar Cells
Stylianakis M.M., Sygletou M., Savva K., Kakavelakis G., Kymakis E., Stratakis E., Advanced Optical Materials, 5, 658-666, 2015[Appeared in the inside front cover of Adv.Opt.Mater]

In-situ Photo-Induced Chemical Doping of Solution-Processed Graphene Oxide for Electronic Applications
Savva K., Lin A.Y-H., Petridis C., Kymakis E., Anthopoulos T.H., Stratakis E., Journal of Materials Chemistry C, 2, 5931-5937, 2014

Improving the efficiency of organic photovoltaics by tuning the work-function of graphene oxide hole transporting layers
Stratakis E., Savva K., Konios D., Petridis C., Kymakis E., Nanoscale, 6, 6925-6931, 2014

Flexible Organic Photovoltaic Cells with In-situ Non-thermal Photoreduction of Spin Coated Graphene Oxide
Kymakis E., Savva K., Stylianakis M. M., Fotakis C., Stratakis E., Advanced Functional Materials, 10.1002/adfm.201202713, 2013


Project Members

Prof. Costas Fotakis
Dr. Emmanuel Stratakis
Dr. Maria Sygletou
Ms. Kyriaki Savva
Dr. Athanasia Kostopoulou
Dr. Minas Stylianakis
Dr. Dimitrios Konios
Mr. Georgios Kakavelakis