Light management for photovoltaics using surface nanostructures Roberta De Angelis Department of Industrial Engineering and INSTM, University of Rome Tor Vergata New Materials For Optoelectronics webnemo.uniroma2.it Credits: M. Casalboni, R. Francini, P. Prosposito, F. De Matteis, L. D Amico (Industrial Engineering Dept., Univ. of Rome Tor Vergata ). A. Di Carlo, D. Barettin, D. Colonna (Electronic Engineering Dept., Univ. of Rome Tor Vergata ), E. Placidi (Physics Dept., Univ. of Rome Tor Vergata ), P. Steglich (TH Wildau).
Development, fabrication and characterization of MATERIALS for applications in NeMO Lab New Materials for Optoelectronic 1. Optics 2. Integrated optics 3. Optoelectronics 4. Energy 5. Sensors
Sol-gel materials SiO 2 TMOS + 4 H 2 O Si(OH) 4 + 4 CH 3 OH
Sol-gel materials SiO 2 TMOS + 4 H 2 O Si(OH) 4 + 4 CH 3 OH
Sol-gel materials SiO 2 TMOS + 4 H 2 O Si(OH) 4 + 4 CH 3 OH
il processo sol-gel: materiali ibridi Hybrid sol-gel materials GLYMO methanol SiO 2
Film deposition Samples: hybrid films Spin coating Dip coating Cast coating Chemical laboratory: synthesis of sol-gel materials by liquid precursors Clean room: class 5000 Deposition: under laminar flow cabin class 100 Substrates: Corning glasses/silicon wafers/fused silica Post-deposition treatment: densification in oven Film thickness: 1 100 m
Film deposition by spin coating H 2 O + acid hydrolysis Dip/spin deposition Heat treatment film substrate Metallic alkoxides in alcohol solvents Viscous gel
Laser interference lithography (LIL) Photopatternable film exposed to UV laser light in Lloyd-mirror configuration. Grating pitch P determined by laser wavelength λ and angle of incidence θ in the range 300 nm - 2 μm. Grating depth D depends on material (sol-gel 300 nm, commercial photoresist 1 μm). sample P 2 sin
Diffraction gratings pitch P sin sin m i m angle of incidence diffraction angle
Soft Lithography and UV-nanoimprinting Mold Fabrication steps by Soft lithography (SL) 1. Poly-Dimethyl-Siloxane (PDMS) silicone rubber is prepared using Sylgard 184 from Dow Corning mixed in 10:1 ratio with its initiator 2. It is poured on the AZ5214 master and held under vacuum to remove air bubbles 3. It is cured, peeled off from the master and cut 14
UV Nanoimprinting PDMS mold allows the realization of high-fidelity replicas of the master grating. Film Substrate Replica Substrate Substrate Substrate PDMS mold can be reused up to 50 times
Light management Dye Solar Cell - DSC SQ2 I 3 - I - I - I - 3 Dye-sensitized TiO 2 FTO-Fluorine doped Tin Oxide Soda-lime float glass
Absorption (o.d.) Light management Dye Solar Cell - DSC 1.75 1.50 SQ2 1.25 1.00 0.75 0.50 0.25 0.00 500 550 600 650 700 Wavelength (nm)
1D Bragg grating nanostructuring Wavelength scale 1D periodic grating on dye sensitized solar cell (DSC). Grating parameters optimization by computational simulations (COMSOL TM ). Novel solar cell design with 1D rectangular grating between the TiO 2 layer and the electrolyte.
1D Bragg grating nanostructuring without grating with grating 700 nm TE polarized light D. Barettin, A. Di Carlo, R. De Angelis, M. Casalboni and P. Prosposito. Opt. Express 20 (S6) A888-A897 (2012).
1D Bragg grating nanostructuring +23.4% light absorption - grating depth 300 nm - pitch 500 nm
Soft Lithography and UV-nanoimprinting Master AZ5214E obtained with Laser Interference Lithography Nanograting of Titania on ITO substrate Replica in PDMS SEM image (ACK Dr. I. Cacciotti) L. D Amico, D. Colonna, R. De Angelis, M. Casalboni, F. De Matteis, A. Di Carlo, P. Prosposito. RSC Advances 4 (2014) 43828-43833.
Transmittance (%) Reflectance (%) UV-nanoimprinting on DSC IPCE (%) 50 2,0 40 30 1,5 20 1,0 10 +15% J SC - +6% V OC - +31% η 0 500 550 600 650 700 750 Wavelength (nm) 0,5 500 550 600 650 700 750 Wavelength (nm) with grating without grating Semi-transparent 3 μm thick TiO 2 layer 2,5 2,0 25 20 Illumination conditions: 100 mw/cm 2, AM 1.5G J (ma/cm 2 ) 1,5 1,0 0,5 (a) 15 10 5 (b) 0,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 Voltage (V) 0 500 550 600 650 700 750 Wavelength (nm)
Light loss by reflection n=1.0 n=1.5 BK7 glass 500 nm light
Moth-eye antireflection layers Credit: Rick Cowen D.G Stavenga, S Foletti, G Palasantzas, K Arikawa Proc. R. Soc. B 2006
Crossed laser interference lithography (c-lil) 2.0µm We obtained 2D structures with pitch in the range 500 nm -2 μm and 100-200 nm in height 1.0µm
Optical characterization of coatings - Refractive index - Thin film Tickness - Transmittance & Reflectance Variable angle spectroscopic ellipsometer (WVASE32 Woollam) - Spectral range 300-1700 nm Total transmittance & reflectance measurement set-up
Transmittance Reflectance (s-pol, i =20 ) Nanocoating Transmission grating depth 100 nm - pitch 1 μm 0,97 0,96 Total transmittance without coating with coating 0,06 0,05 0,95 0,94 0,04 0,93 0,92 520 560 600 640 680 720 760 800 wavelength (nm) 0,03 0,02 400 500 600 700 800 900 Wavelength (nm) without coating with coating
Permanent staff: Prof. Mauro Casalboni Prof. Roberto Francini Dr. Paolo Prosposito Dr. Fabio De Matteis Post-doc: Dr. Roberta De Angelis Thank you for your attention. Ph.D student: Dr. Liliana D Amico
DSC modeling
DSC modeling
Grating size optimization
Grating structural characterization AZ 4521E - grating depth 200 nm - pitch 500 nm TiO 2 - grating depth 130 nm - pitch 500 nm ACK Dr. E. Placidi, Dr. I. Cacciotti