Research on Renewables: a Case Study Third generation solar cells: DSSC

Research on Renewables: a Case Study Third generation solar cells: DSSC Alessandro Mordini CNR Istituto di Chimica dei Composti Organometallici Area di Ricerca di Firenze Surpassing Energy Targets through Efficient Public Buildings Firenze, Salone dei Dugento, Palazzo Vecchio 21 November 2014

Research on renewable energies through a highly multidisciplinary approach «Design and Synthesis of new organic dyes for the production of non-conventional solar cells» from: May 2010 until April 2013 www.fotosensorg.unisi.it «IRIS - Coloranti per l energia e l ambiente» from: May 2012 iris.iccom.cnr.it

Humanity has constantly increased its energy need and consumption. Global energy consumption in 2010:12 Btoe = 139.600 TWh (+5.6% compared to 2009). Most of this energy is produced by fossil fuel. Result: resources shortage of fossil fuel resources and atmospheric and environmental pollution. Source: Innovative Clean Energy 2030 Inc. Energy (2008) Outlook (BP) Unless major and urgent changes are made in supply/demand management of energy and/or alternative Energies are made sufficiently available, the maximum supportable worldwide human population level will peak between 2025 and 2050 Europe 2020 Initiative 1) -20% greenhouse gas emissions 2) +20% energy efficiency 3) 20% from renewable sources http://ec.europa.eu/europe2020/index_en.htm

SOLAR ENERGY IS FREE AND PRACTICALLY INEXHAUSTIBLE The volume of the spheres represents the amount of energy potentially (although perhaps not practically) available from every renewable source, together with global consumption in year 2010 Source: Perez et al.,iea/shc, A fundamental look at energy reserve in the planet Italy (16%) and Germany (32%) combined accounted for nearly half of global solar PV capacity Source: Renewables 2013 Global Status Report

Main Classes of Photovoltaic Cells 1) Silicon-Based Solar Cells a) Monocrystalline silicon b) Polycrystalline silicon Market share: ~ 80%* 2) Thin Film Solar Cells a) GaAs b) CdTe c) CI(G)S CuIn(Ga)Se 2 d) Amorphous silicon (a-sih) Market share: ~ 20%* 3) Organic and Hybrid Solar Cells a) Bulk heterojunction solar cells (OPV) b) Dye-Sensitized Solar Cells (DSSC) *Source: EPIA (2010) Optimized performances Non-optimized performances Old generation New generation

Record DSSC

DSSC have been invented in 1991 by the german chemist Michael Grätzel at EPFL - Lausanne (Switzerland). Main features- pros Good cells efficiencies (η max > 12%, lab scale). Performances relatively independent by irradiation conditions. Michael Grätzel Raw material easily available and low cost production. Possible use of different supports (glass, polymeric materials). Construction of either transparent or opaque cells in different colours. Limitations- cons Modules efficiency still too low (tipically between 6% and 9%). Stability and lifetime, despite continuosly increasing, not satisfactory yet (problems: corrosion, leak of material, degradation). Limited number of practical applications (prototypes, small electronic devices).

Cost of module production DSSC: 1.21 $/W p (Solaronix, 2009) c-si:1.40-1.75 $/W p (GTM Research, 2010) Thin Films (CdTe): < 1 $/W p (First Solar, 2011) Production costs: Raw materials: Energy Payback Time (EPBT) Growth Rate Forecast LCA analysis: Major out-comes show that DSSCs compare similarly and are sometimes better than inorganic thin film devices, even for a far-from-optimum industrial fabrication procedure. M. L. Parisi, S. Maranghi, R. Basosi Renew. Sust. Energ. Rev. 39 (2014)124 138

Japanese company Fujikura has performed detailed investigations on the relationship between solar radiation and DSSC modules performances. Light intensity Incident angle Temperature effect

Due to their better performances under diffuse light, DSSC modules of the same nominal power produce more energy compared to p-si modules (approximately1.6 times higher on the north wall).

Accelerated tests with solar simulator 20.000 h = 2 y 103 d In these conditions the duration of the test is assumed to correspond to a real utilization lenght of 20 years however, bear in mind this is only a simulation!

Test under real conditions of use J sc V oc After around 2.5 years module efficiency was still above 80% of the initial value Deterioration factor: 0.02% / day FF η N. Kato et al., Sol. Energy Mater. Sol. Cells 2009, 93, 893.

Some commercial applications backpack with small flexible DSSC panels for recharging batteries of portable electronic devices (e.g. mobile phones, mp3 players etc.) Folio Solar Keyboard a new ipad cover endowed with a DSSC-powered keyboard. Hana Akari, Flower Lamp

Forecasted growth of DSSCs in different market segments Source: IDTechEx report Dye Sensitized Solar Cells 2013-2023: Technologies, Markets, Players Ease transition to: EPFL, Lausanne Building-Adapted PhotoVoltaics Building-Integrated PhotoVoltaics

BIPV: Building Integrated PhotoVoltaics Toyota «Dream House», Aichi CSIRO Energy Centre, Newcastle House of the Future Prototype, OlympicVillage, Sydney

EPFL Conference Center (Solaronix, CH)

Geneva Airport (g2e, CH) Prototypes of Solar Windows (Dyesol, AUS)

Projet BIPV - Gare TGV de Perpignan (ISSOL Belgium) See-through solar energy panel (Sharp, Jpn)

Renovation of MGM Hotel Las Vegas DSSCs mounted on Motorized Blinds over the windows, power a DC motor and enable the user to control the solar shading with the use of a remote or wall mounted switch.

Indoor application Electronic Shelf Labels (ESL) Update the prices daily via the RF transmission technology TV remote control Sensors

Glass Transparent Conductive Oxide TiO 2 Glass Electrolyte Solution (I - /I 3- ) Platinum Dye Dye: 1. Improvement of light absorption and electonic transfer properties. 2. Simpler and more efficient synthetic procedures. 3. New dyes for transparent materials and for new colours. TiO 2 : Studies on the morphology and size of nanopartcles; superficial modifications. Electrolytic solution: Synthesis and application of (metall)organic compounds as an alternative to the usual redox couple iodide/triiodide; studies on the use of non volatile solvents and solid phase electrolytes.

Mechanism 1. Light absorption 2. Photoexcitation 3. Injection 4. Charge collection 5. Electrolyte reduction 6. Regeneration In the DSSCs the functions of photon absorption and charge separation/ transport are made by different components.

Dyes (sensitizer): ideal properties a) Broad and efficient light absorption in the visible and near-infrared region ( -conjugation). b) Should have functional groups allowing a good anchoring on TiO 2 (COOH). c) Its energy levels should be correctly aligned to ease regeneration and electron injection. d) It should not aggregate on the surface of the semiconductor (alkyl chains). e) It should be thermally, chemically and photochemically stable. f) For application in BIPV must be designed in different colours and transparency. Test cells ready for stress measurements

Computational analysis FEEDBACK Design of new organic photosensitizers Assembly of laboratory cells and efficiency measurements Laboratory synthesis Characterization

Structural design supported by TD-DFT calculations Donor Group -Spacer Acceptor Group acceptor group TiO 2 donor group -spacer Tuning of the energy levels and of the HOMO-LUMO gap Influence on color (λ max ), intensity of absorption (ε) Increase in the stability of the dye/semicondutor assembly Influence on electron transfer and device lifetime

Daniele Franchi, Massimo Calamante Tetrahedron (Symposium-in-Print) 2014, 70, 6285 Firenze, 21 November 2014 Efficiency measurements Compound CDCA best η (%) DF13A 3.14 DF13B + 3.24 DF13C + 3.02 DF15 + 6.04 Desorption kinetics from TiO 2 Cell stability over 1000 h KOH 0.1 M in EtOH

2 nd Generation dyes 510 < max < 521 nm in all cases. Molar extinction coeffcients > 80000. Clear improvement of the electronic, optical and physico-chemical properties compared to previous gen. TTZ3-5: Chem. Commun. 2014, DOI: 10.1039/C4CC06160H

2 nd Generation dyes Consistent with our aims: tests significant toward possible application in BIPV Simple fabrication: NO TiCl 4 treatment, NO scattering layer, I /I 3 redox couple Thin TiO 2 films: 5.5 μm (transparent) 6.5 μm (opaque) J-V curves Stability Test 1000h ageing in the dark @ 85 C Best cell efficiency: = 7.39-7.71% for TTZ5 (transparent ad opaque cells, respectively). Performances superior to reference dyes D5 (organic) and Z907 (Ru-based). Daniele Colonna (C.H.O.S.E, Roma) TTZ3-5: Chem. Commun. 2014, DOI: 10.1039/C4CC06160H

Research on renewable energies through a highly multidisciplinary approach «Design and Synthesis of new organic dyes for the production of non-conventional solar cells» from: May 2010 until April 2013 www.fotosensorg.unisi.it «IRIS - Coloranti per l energia e l ambiente» from: May 2012 iris.iccom.cnr.it

Progetto FAR FAS 2014 Selfie: Sistema di Elementi avanzati multi Layer basato su superfici e materiali Innovativi nanostrutturati per una Edilizia sostenibile ed energeticamente efficiente Pannelli fotovoltaici di terza generazione integrati in architettura Progetto POR FESR 2014-2020 Encolor Design: ENergia rinnovabile da pannelli fotovoltaici COLORati architettonicamente integrati Pannelli fotovoltaici di terza generazione integrati in architettura

Progetto Smart Cities and Communities (MIUR) Smartgate plus: Smart Solution for a Transparent, Efficient, and more Sustainable Administrative Justice Riqualificazione energetica di edifici di pregio sedi di tribunali amministrativi Progetto Ente Cassa di Risparmio di Firenze IRIS: Coloranti per l energia e l ambiente Progettazione, preparazione e caratterizzazione di nuovi materiali per celle DSSC

Acknowledgments CNR-ICCOM Dr. Gianna Reginato Dr. Lorenzo Zani Dr. Massimo Calamante Dr. Grabriella Barozzino Alessio Dessì Bianca Cecconi Daniele Franchi Damiano Cirri Ottavia Bettucci Giovanna Burgio Rocco De Lorenzo Matteo Bessi Marco Monini Dr. Maurizio Peruzzini Università degli Studi di Siena Prof. Maurizio Taddei Dr. Fabrizia Fabrizi de Biani Prof. Riccardo Basosi Dr. Adalgisa Sinicropi C.H.O.S.E - Università di Roma «Tor Vergata» Prof. Aldo di Carlo Dr. Daniele Colonna «FOTOSENSORG» Project (2010-2013) Funding Università degli Studi di Firenze Prof. Mara Bruzzi Dr. Riccardo Mori Michele Spatola Prof. Roberto Bianchini Dr. Marco Corsi Dr. Marco Bonanni «IRIS» Project (2013-2015) Progetto Premiale «Energia da fonti rinnovabili» 24

Richiamo a serpente Building trasparenti: importanza

Photovoltaic Cell: a device capable of converting sunlight into electricity Main classes of photovoltaic cells: Silicon-Based Solar Cells Monocrystalline silicon Polycrystalline silicon Old generation Optimized performances Thin Film Solar Cells GaAs CdTe CI(G)S CuIn(Ga)Se 2 Amorphous silicon Organic and Hybrid Solar Cells Organic solar cells (OSC) Dye-Sensitized Solar Cells (DSSC) Perovskite Solar Cells New generation Non-optimized performances P max Efficiency: η = = P in J sc V oc ff P in P max : maximum power produced by the cell P in : power of incident solar radiation Mettere performance s It should always be coupled with a good stability! Current/Voltage (J/V) curve

Dyes (sensitizer): design, synthesis and characterization A multidisciplinary approach Progetti in corso, citare horizon 2020 e serpente, regione, comune

DSSC: Progetti in corso Progetto Smart Cities and Communities (MIUR) Smartgate: Giustizia Amministrativa Riqualificazione energetica di edifici di pregio sedi di tribunali amministrativi Palazzo spada, Roma Sede dell Consiglio di Stato Progetto Nazionale in corso di valutazione 1 Forum Internazionale, Sviluppo Ambiente Salute, Arezzo, 22.11.2012

Main Classes of Photovoltaic Cells 1) Silicon-Based Solar Cells a) Monocrystalline silicon b) Polycrystalline silicon Market share: ~ 80%* 2) Thin Film Solar Cells a) GaAs b) CdTe c) CI(G)S CuIn(Ga)Se 2 d) Amorphous silicon (a-sih) Market share: ~ 20%* 3) Organic and Hybrid Solar Cells a) Bulk heterojunction solar cells (OPV) b) Dye-Sensitized Solar Cells (DSSC) *Source: EPIA (2010)

Dyes (sensitizer): ideal properties a) Broad and efficient light absorption in the visible and near-infrared region ( -conjugation). b) Should have functional groups allowing a good anchoring on TiO 2 (COOH). c) Its energy levels should be correctly aligned to ease regeneration and electron injection. d) It should not aggregate on the surface of the semiconductor (alkyl chains). e) It should be thermally, chemically and photochemically stable. f) For application in BIPV must be designed in different colours and transparency.

The development of this technology is well suited for small and medium size companies dealing with all the manufacturing indicated below CELLS PRODUCTION Glass manufacturer Supports (plastic, metal) Electrodeposition Semiconductor Cell printing APPLICATION Housing components Furniture Accessories Lamps Doors, windows. INNOVATION IN DESIGN Opportunity for coupling made in Italy and technology

DSSC: Materials and Structure Glass Transparent Conductive Oxide Electrolyte Solution (I - /I 3- ) Platinum TiO 2 Dye Glass Components 1. Glass substrate 2. TCO layer (transparent conductive oxide) 3. Nanocrystalline semiconductor (TiO 2 ) 4. Dye (adsorbed on the semiconductor) 5. Electrolyte solution 6. Counter electrode (usually Pt) 7. Glass substrate http://www.solarprint.ie/images/dssc.jpg Alessandro Mordini EUSEW, Bruxelles, 22.06.2012 7/13

DSSC: Mechanism Mechanism 1. Light absorption 2. Photoexcitation 3. Injection 4. Charge collection 5. Electrolyte reduction 6. Regeneration Nelle DSSC il processo di assorbimento della luce e quello di separazione/trasporto dei portatori di carica sono svolti da due componenti distinti. Alessandro Mordini EUSEW, Bruxelles, 22.06.2012 7/17

Solar radiation spectrum Solar radiation should be adsorbed in the visibile and near infrared. Alessandro Mordini EUSEW, Bruxelles, 22.06.2012 2/17