Scaling of Dye Solar Cells: from single cells to modules and panels Stefano Penna, Riccardo Riccitelli, Eleonora Petrolati, Andrea Reale, Thomas M. Brown, Aldo Di Carlo Centre for Hybrid and Organic Solar Energy (CHOSE) Department of Electronic Engineering, University of Rome “Tor Vergata” PLMCN10, Cuernavaca (Mex) April, 2010

PLMCN10, Cuernavaca (MEX) April, 2010 Outline Introduction to Dye Solar Cells Optimization strategies for efficiency improvement Upscaling: from DSC test cells to modules and panels Conclusions

PLMCN10, Cuernavaca (MEX) April, 2010 Centre for Hybrid and Organic Solar Energy Set in 2007 upon Lazio Region 3-year funding – 600 m 2 lab facilities in the Hi-Tech District of Rome (Tecnopolo Tiburtino) – 50 people: 5 Prof, 5 Assistant Prof, 9 Post Doc, 20 PhD, 11 post-grad Totally focused on Organic and Hybrid Photovoltaic technologies – Materials – Processing towards inline automation – Up-scaling towards large area devices – Modeling and simulation tools Technological Transfer to industry – Two spin-off companies hosted – Dyers for technology development – TiberCAD for modeling – Industrial partnership within Dyepower 51% CHOSE

PLMCN10, Cuernavaca (MEX) April, 2010 Structure of a DSC Dye Molecules on TiO 2 Glass Substrate Electrolyte I - /I - 3 Catalyst (Platinum, graphite) Glass Substrate Transparent Conducting Oxide (FTO ) nanostructured TiO 2

PLMCN10, Cuernavaca (MEX) April, 2010 Working principle of a DSC I3-I3- I-I- Red No permanent chemical transformation in the materials composing the cell 2S + + 3I - 2S + I 3 - I e - 3I - S + hvS* S + + e − (TiO 2 ) Titania (10  m) Dye Electrolyte (50  m) Catalyst (10 nm)

PLMCN10, Cuernavaca (MEX) April, 2010 Unique aesthetical features Colour tuning, Transparency Customized patterning

PLMCN10, Cuernavaca (MEX) April, 2010 “New” manufacturing process High temperature, doping, vacuum pocessing Conventional Electronics Organic Electronics Printing methods Conventional semiconductor industry Large enterprises (tens of M€ fab) Small Medium enterprises (some M€ fab) Liquid deposition

PLMCN10, Cuernavaca (MEX) April, 2010 Other advantages of DSC technology Lower fabrication cost than Silicon PV – In DSC cost imposed by processing – In Silicon PV 80% cost imposed by silicon wafer production Ideal for Building Integration – Indipendent on lighting angle – Better working under scattered light than direct light – Availability for transparency, colour tuning, customized patterning Higher energy produced during 1 year than Silicon PV upon the same W p installed, despite lower W p efficiency (11% vs 25% on lab cells) Lower fab cost  lower entrance barrier for investors Lower energy payback High environmental compatibility

PLMCN10, Cuernavaca (MEX) April, 2010 Optimization parameters TiO 2 Electrolyte Counter-Electrode Encapsulation Layout Printing Technique Dye Easy Medium Critical Difficult

Dyes Natural Dyes Industrial Dyes Organic Dyes Rutenium-Based Dyes Efficiency 1% 11% N719 Dye

PLMCN10, Cuernavaca (MEX) April, 2010 Dye management Spectral response can be enlarged by a double-dye strategy involving an IR absorber beyond the green absorber (N719 and similar) Colonna, Di Carlo, Bignozzi, Brown, Reale et al., under submission Absorbance External Quantum Efficiency

PLMCN10, Cuernavaca (MEX) April, 2010 TiO2 management: standard performance

PLMCN10, Cuernavaca (MEX) April, 2010 TiO2 management Tayloring the TiO 2 surface by the use of Scattering Layers (SLs) to trap light in the working electrode D. Colonna et al. / Superlattices and Microstructures 47 (2010) % S. Ito et al., Adv. Mater. 2006, 18, 1202–1205

PLMCN10, Cuernavaca (MEX) April, 2010 Upscaling: from test cells to modules In a test cell performances are ruled by materials In large area cells and modules performances are ruled by technology – large area deposition – sealing and encapsulation – high series resistance of TCO electrodes (8  sq)  interconnections among cells needed Test cell (0.5 x 0.5 cm 2 ) Module 10 x 20 cm 2

PLMCN10, Cuernavaca (MEX) April, 2010 Module lay-out Z-configuration – series connection – ideal for BIPV – interconnection dispensing is critical W-configuration – series connection – no need for interconnection dispensing – not good for BIPV – problem with electrical balancing P-configuration – parallel connection – grid dispensing is less critical ++     + Pictures courtesy of

PLMCN10, Cuernavaca (MEX) April, 2010 Module performance Micro vertical interconnections (20 micron) for high level of transparency Micro-interconnections (Z) 37 cm 2 module with 4 Z micro-interconnected cells (cell area = 9.4 cm 2 ).

PLMCN10, Cuernavaca (MEX) April, 2010 Large area: from modules to panels Panel 0.8 x 0.6 m 2 Module 20 x 10 cm 2

PLMCN10, Cuernavaca (MEX) April, 2010 String assembly: the beginning

PLMCN10, Cuernavaca (MEX) April, 2010 Panel lay-out 20 Modules: 4 strings of 5 Modules Series Interconnected Panels 0.8 x 0.6 = 0.48 m 2 First DSC CHOSE

PLMCN10, Cuernavaca (MEX) April, 2010 Strings composition Series interconnected DSC module  Nickel conducting paste

PLMCN10, Cuernavaca (MEX) April, 2010 DSC Strings performance Higher current production in Z strings Higher voltage in W strings (one cell more per module) Better fitting in W strings + + Z-type W-type  = 5.03 %  = 3.34 %

PLMCN10, Cuernavaca (MEX) April, 2010 Panel assembly Strings are aligned on a glass slab, protected by soldering bypass diodes (one per module) and parallel connected by bus bar Glass lamination and Silicone filling for protection, UV filtering and higher resistance to environmental and mechanical stress

PLMCN10, Cuernavaca (MEX) April, 2010 The result

PLMCN10, Cuernavaca (MEX) April, 2010 Panels performance Outdoor testing at 1 sun (1000 W/m 2 ) Panel perpendicular at sun light

PLMCN10, Cuernavaca (MEX) April, 2010 PV CELL Traditional Photovoltaic Applications 25

PLMCN10, Cuernavaca (MEX) April, 2010 Innovative PV applications

PLMCN10, Cuernavaca (MEX) April, 2010 CHOSE within Dyepower Consortium 10 M€ framework agreement for the industrialization of DSC based continous glass envelopes for real BIPV Transparency and aesthetics have primary roles in the development step Automation purposed approach as a fundamental guide line

PLMCN10, Cuernavaca (MEX) April, 2010 Conclusions Upscaling from cell to module is not trivial, but proper engineering on modules lay-out and deposition technologies can reduce the drop of efficiency Final upscaling from module to string and panel is less difficult, even if additional aesthetical issues must be considered Final target of 5% efficiency on DSC panel is not far Long term stability is the last hurdle for commercialization … … but we’re workin on it !

PLMCN10, Cuernavaca (MEX) April, 2010 Acknowledgments Collaborators: Univ. Ferrara, Chemistry Dep. (Prof. Bebo Bignozzi) Sapienza Univ. Rome, Energy Dep. (Prof. Michelotti, Dr. Dominici) Sapienza Univ. Rome, Chemistry Dep. (Prof. Decker) Univ. Rome Tor Vergata, Physics Dep. (Maestro Pino Eramo) Univ. Turin, Chemistry Dep. (Prof. Viscardi) Regione Puglia, Ass. “Nessuno Tocchi Raffaele” Univ. Sevilla, (Prof. Colodrero) All CHOSE, special thanks to: Daniele Colonna Alessandro Lanuti Simone Mastroianni Lorenzo Dominici