Soft lithography for diffractive microfabrications Liliana D Amico PhD Section: Materials Engineering XXVIII Cycle (3 Year) Mauro Casalboni, Fabio De Matteis, Paolo Prosposito, Roberta De Angelis
Summary Diffractive elements in Optoelectonic Method & materials to fabricate Bragg gratings Introduction to soft lithography & PDMS Properties DSC: Titania layer nanostructuring to enhance cell efficiency Recent challanges
Diffractive elements in optoelectronics Diffraction gratings are often used as dispersive elements in monochromators, spectrometers, lasers, filters. Recently in photovoltaic applications for Light Management Techniques to realize light trapping schemes Scattering layers or centers materials of different morphologies able to confine light in TiO2 layer Photonic crystals Highly reflecting layers Periodic structures on the top side Coupling/diffracting elements H. Chang et al; Journal of Solid State Science and Technology, 2014. D.Colonna et al; Energy & Environmental Science, 2012.
How to realize diffractive Bragg Grating
Laser Interference Lithography (LIL) 1. Photoresist AZ5214E 2. Spin coating Laser Ar + 3. Exposition/Lloyd Mirror configuration sin m 2 Mirror
How to easily & faithfully replicate diffractive patterns on different substrates?
How to easily & faithfully replicate diffractive patterns on different substrates? SOFT LITHOGRAPHY
Introduction to Technique Soft lithography is a non conventional lithographic process based on the use of «soft materials» like organic polymers to perform replication & patterning transfer for carrying out micro- and nanofabrication molding Replication Pattern transfer
1.Molding PDMS - Polydimethylsiloxane A unique combination of properties resulting from the presence of an inorganic siloxane backbone and organic methyl groups attached to silicon. Main Properties: Very low glass transition temperatures (fluid at room temperature); Can be readily converted into flexible solid elastomer by cross-linking; Optically transparent from 235 nm to near IR; Biocompatible; Inert & Non toxic; Not flammable and gas permeable; Thermally & electrically isulating.
2. Replication Master Diffractive pattern Heat treatment under vacuum peeling Final mold Can replicate nanostructures in one step over large areas; Convenient, effective, and low-cost; Enable the fabrication on nonplanar surfaces with a wide range of materials.
3.Pattern Transfer on DSC TiO 2 layer
Theoretical Prediction Calculations based on 2D - FEM with COMSOL Multiphysics TM To enhance cell efficiency
Theoretical Prediction Calculations based on 2D - FEM with COMSOL Multiphysics TM To enhance cell efficiency
Theoretical Prediction Calculations based on 2D - FEM with COMSOL Multiphysics TM To enhance cell efficiency ᴧ = 500 nm h = 300 nm
Theoretical Prediction Traditional cell vs nanostructured cell Redistribution of radiation in bunches owing to diffraction effects D. Barettin, A. Di Carlo, R. De Angelis, M. Casalboni and P. Prosposito. Opt. Express 20 (S6) A888-A897 (2012). Absorption enhancement, in the range 500-700 nm +23.4%
DSC layer nanostructuring UV-Nanoimprinting of TiO2 layer
DSC layer nanostructuring UV-Nanoimprinting of TiO2 layer
Morphological characterization ACK Dr. E. Placidi, Dr. I. Cacciotti
Optical characterization Integrating sphere system measurements 50 2,0 Transmittance (%) 40 30 20 10 (a) 0 500 550 600 650 700 750 Reflectance (%) 1,5 1,0 (b) Legend: Standard cell Nanostructured 0,5 500 550 600 650 700 750 Wavelength (nm) Wavelength (nm) Lower transmittance and lower reflectance means enhanced absorption Collaboration
Photovoltaic characterization Legend: Standard cell Nanostructured +15% Density of current (J SC ) +6% Voltage (V OC ) +32% of IPCE L. D Amico, D. Colonna, R. De Angelis, M. Casalboni, F. De Matteis, A. Di Carlo, P. Prosposito. RSC Advances 4 (2014) 43828-43833. Collaboration
Recent Challange: Large area replication 0,25 cm 2 greater by a factor of 10! 2,5 cm 2 E. Calabrò. Tesi Magistrale in Scienze e Tecnologie dei Materiali. «Ottimizzazione di Perovskite Solar cell e DSC mediante reticoli di Bragg di larga area. 2015. Collaboration
Recent Challange: 2D Structures & Replication 0,06 Reflectance (s-pol, i =20 ) 0,05 0,04 0,03 0,02 400 500 600 700 800 900 Wavelength (nm) without coating with coating Collaboration
Thank you for attention!
Pubblications & other activieties [1] R. De Angelis, L. D Amico, M. Casalboni, F. Hatami, W.T. Masselink, P. Prosposito, Surface InP Quantum Dots: Effect of Morphology on the Photoluminescence Sensitivity ; Procedia Engineering, 26th European Conference on Solid-State Transducers, EUROSENSORS 2012. [2] R. De Angelis, L. D Amico, M. Casalboni, F. Hatami, W.T. Masselink, P. Prosposito, Photoluminescence sensitivity to methanol vapours of surface InP quantum dot: Effect of dot size and coverage ; Sensors and Actuators B: Chemical, February 2013. [3] R. De Angelis, M. Casalboni, I. Colantoni, L. D Amico, F. De Matteis, F. Hatami, W.T. Masselink, P. Prosposito. Luminescence sensitivity investigations on epitaxial surface InP quantum dots ; Journal of Sensor Technology, 2013. [4] R. De Angelis, Ilaria Fratoddi, F. De Matteis, P. Prosposito, I. Cacciotti, L. D'Amico, F. Nanni, A.Yadav, M. Casalboni, M. V Russo. From nanospheres to microribbons: self-assembled Eosin Y doped PMMA nanoparticles as photonic crystals ; Journal of Colloid Interface Sci.,2013. [5] R. De Angelis, M. Casalboni, L. D Amico, F. De Matteis, F. Hatami, W. T. Masselink, P. Prosposito. Vapour sensitivity of InP Surface Quantum Dots, Accepted for publication in Key Engineering Materials, 2013. [6] L. D Amico, D. Colonna, R. De Angelis, M. Casalboni, F. De Matteis, A. Di Carlo, P. Prosposito. Bragg grating Nanostructuring of TiO 2 layer in dye sensitized solar cells: an efficien method to enhance light harvesting. RSC Advances, 2014. Symposium: Innovative solar cells for renewable and sustainable energy production, Milan 18 December 2013. Bragg grating nanostructuring for light harvesting in Dye Sensitized Solar Cells (talk) Tutoring Activity Physics 1 excercises