Light Management in 3D Structured Glass for High Efficiency Building Integrated Dye Sensitized Solar Cells
Luca Passoni a, Francesco Fumagalli a, Fabio Di Fonzo a, Marco Beghi b
a Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Pascol 70/3, Milan, 20133, Italy
b NEMAS—Center for NanoEngineered MAterials and Surfaces, Dipartimento di Chimica, Materiali e Ingegneria Chimica “G. Natta”, Politecnico di Milano, , Piazza Leonardo da Vinci 32, 20133 Milano
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, Luca Passoni, 207
Publication date: 1st March 2014

Building Integrated Photovoltaics (BIPV) is the main pathway for future development of the PV market as set by regulators and proper soil usage. In general, BIPV suffers of an efficiency loss due to non-optimal orientation. Non-normal irradiance due to PV elements locked orientation and optical losses due to reflection at the glass/air interface for high incidence angles are the two main mechanisms decreasing short-circuit current level related to BIPV module orientation with respect to sun position. Lack of transparency and fixed coloration of commercially available silicon-based PV modules are another major technical limitation for BIPV applications.

In order to overcome these issues we developed a novel three dimensional structured glass (TDSG) coated with F-doped SnO (FTO) transparent conducting oxide as substrate for a DSC thin film solar cells. TDSG geometries acts as low intensity solar concentrator (< 10 suns) and are modelled by means of dedicated ray tracing simulations in order to minimize reflection losses and optimize light trapping; higher efficiency at non-normal incidence and increase in carrier generation rate is observed as compared to flat glass reference. TiO2 photoanodes consisting of anatase single crystals assembled in quasi 1-D arrays of high aspect ratio hierarchical mesostructures1,2 are fabricated onto the TDSG glass light harvesting surfaces by self-assembly from the gas phase. Structural and morphological characteristics of TiO2 nanostructured photoanodes are optimized to achieve simultaneously high specific surface area for optimal dye uptake and broadband light scattering. Acting on widely different length scales, nanostructures light scattering and solar concentration TDSG geometries are combined in order to maximize photons path length into the absorber and the overall efficiency of the system.

The three-dimensional substrate required careful optimization of the transparent conductive oxide and TiO2 photoanodes deposition parameters. Monolithic configuration, needing only the photoanode glass support, can be used in place of a standard sandwich-like liquid-DSC to address the module weight minimization issue. Measurements of test cells under different illumination conditions are performed via a variable angle support stage under solar simulator.

Use of DSC for BIPV applications allows the fabrication of semi-transparent modules with tuneable chromatic characteristics; moreover best performance for TDSG systems is obtained at low angle of incidence, which makes the DSC-TDSG coupled device particularly suitable for building integrated photovoltaics.


A) Sun altitude during different times of year for typical BIPV configuration B) Sun concentrating strategy for three dimensional structured glass (TDSG). C) Ray tracing simulation of light propagation within the cross section of a TDSG. D) SEM cross sectional images of nanostructured mesoporous TiO2 photoanode. E) Example of TDSG substrate coated with indium-doped tin oxide transparent contact and mesoporous TiO2 photoanodes loaded with N719 Ru-based dye before encapsulation.
1. Passoni, L.; Ghods, F.; Docampo, P.; Abrusci, A.; Martí-Rujas, J.; Ghidelli, M.; Divitini, G.; Ducati, C.; Binda, M.; Guarnera, S.; Li Bassi, A.; Casari, C. S.; Snaith, H. J.; Petrozza, A.; Di Fonzo, F. Hyperbranched Quasi-1D Nanostructures for Solid-State Dye-Sensitized Solar Cells. ACS Nano 2013, 7, 10023-10031. 2. Sauvage, F.; Di Fonzo, F.; Li Bassi, A.; Casari, C. S.; Russo, V.; Divitini, G.; Ducati, C.; Bottani, C. E.; Comte, P.; Graetzel, M. Hierarchical TiO2 Photoanode for Dye-Sensitized Solar Cells. Nano Letters 2010, 10, 2562-2567.
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