Dynamic modulation of the optical transmittance in dye-sensitized photovoltachromic devices
Simone Valente a, Roberto Giannuzzi a, Michele Manca a, Fabio Di Fonzo b, Mehrdad Balandeh b, Giuseppe Gigli c, Guido Viscardi d, Claudia Barolo d
a Center for Biomolecular Nanotechnologies (CBN), Fondazione Istituto Italiano di Tecnologia (IIT), Lecce, IT, Via Barsanti 1, Arnesano, 73010, Lecce, Italy
b NNL, National Nanotechnology Laboratory, CNR Istituto Nanoscienze, Distretto Tecnologico, Via Arnesano km 5, 73100 Lecce, Italy, Italy
c University of Torino, Department of Chemistry and NIS Interdepartmental Centre, Via Pietro Giuria 7, 10125, Torino
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Poster, Michele Manca, 138
Publication date: 1st March 2014

A photovoltachromic cell may potentially act as a complex artificial skin, by generating electric energy as a photovoltaic system but even ‘‘perceiving’’ small variations in external radiation and controlling the energy fluxes by means of a smart variation of their optical transmittance.

To this aim we recently developed a specifically designed bi-functional counter electrodes made of two physically separated regions, respectively displaying as a catalytic and an electrochromic function.1

Incoming solar light is partially harvested by a dye-sensitized photoelectrode made on the front glass of the cell which fully overlaps a bi-functional counter. When the cell is illuminated, the photovoltage drives electrons into the electrochromic stripes through the photoelectrochromic circuit and promotes the Li+ diffusion towards the electrochromic region, which thus turns in its colored state.  At the same time an efficient photovoltaic functionality is executed by the catalytic region. Several different combinations of dyes2,3,4 (characterized by narrow absorption spectra with complementary colors) and electrochromic materials (either produced by colloidal routes 5 or by pulsed laser deposition 6) have been explored along with several specific device architectures. These devices can potentially pave the way to the effectivedevelopment of large-area multifunctional smart windows to be integrated in the next generation of building glass facades. A photocoloration efficiency of about 45 cm2*min-1*W-1 has been demonstrated under 1.0 sun illumination along with fast response (coloration time < 2 sec and bleaching time < 5 sec). Regarding the PV functionality, a power conversion efficiency ranging from 2% to 5% is achievable depending on the light absorbing prerogatives of the dye-sensitized electrode as well as on the electrolyte’s chemical composition. 


Figure 1. Schematic representation of a photovoltachromic device. Different dyes have been used to control chromatic coordinates, namely two squaraine dyes (VG1-C8 (ref2) and VG5 (ref3)) absorbing in the red/near-IR region and a carbazole dye (DYE1 (ref4)) absorbing in the blue region.
[1] Cannavale A. et al. En. Environ. Sci., 2011, 4, 2567 [2] Park J. Et al. Chem. Commun., 2012, 48, 2782–2784 [3] Magistris C. Et al. Ren. Energy, 2013 , 60, 672-678 [4] Grisorio R. et al Dyes Pigm., 2013, 98, 221-231 [5] Giannuzzi R. et al. Appl. Mat. Int., 2014, DOI: 10.1021/am4049833 [6] Passoni L. et al. ACS Nano, 2013, 7 (11), 10023–10031
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