TiO2 for hybrid solar cells and its application in large area plastic dye solar cells and high efficiency perovskite solar cells
Thomas M. Brown a, Aldo Di Carlo a, Andrea Reale a, Francesco Di Giacomo a, Valerio Zardetto a d, Alessandra D'Epifanio b, Silvia Licoccia b, Irfan Ahmed c, Azhar Fakharuddin c, Rajan Jose c
a CHOSE - Centre for Hybrid and Organic Solar Energy, University of Rome ‘‘Tor Vergata’’, Via del Politecnico, 1, Roma, Italy
b University of Rome Tor Vergata, Department of Chemical Science and Technologies, Italy, Via della Ricerca Scientifica, 1, Roma, Italy
c Faculty of Industrial Sciences and Technology (FIST), Universiti Malaysia Pahang, 26300 Kuantan, Malaysia
d Eindhoven University of Technology, Department of Applied Physics, 5600MB, Eindhoven, Netherlands
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, Francesco Di Giacomo, 389
Publication date: 1st March 2014

Wide band gap n-type TiO2 nanostructured layers are typically used as electron extractors and transport layers in hybrid solar cells owning to theirsuitable properties of electron mobility, stability and desired energy levels for efficient electron injection from the absorbing layers. In particular TiO2 is an efficient electron acceptor for dye sensitizers and even for hybrid organo-lead-halide perovskite materials. Here we present applications of various TiO2 formulations and morphologies applied to large area flexible dye solar cells and to mesostructured perovskite solar cell.

 

Firstly, a UV irradiation process was employed, as an alternative to high temperature treatment, to fabricate both of the plastic electrodes (working and counter) in flexible dye solar cells (DSCs) and modules. UV treatment induces both complete removal of organic binders present in TiO2 paste and increased charge collection as confirmed by electrochemical impedance spectroscopy. It also determines effective photoplatinization of the counterelectrode. An overall efficiency (η) of 4.2% was achieved in singles cells of area 0.25 cm2.The formulations and processes (printing + irradiation) developed for both  DSC electrodes are simple, and easily up scaled over large areas as demonstrated with the first module (16.4 cm2) on plastic realized with a W series interconnection (PCE = 2.6%) [1].

 

Water based TiO2 formulations  are complex to screen print. Here we present a screen printable formulation comprising a cellulose binder and a high boiling point additive in water. Using screen printing and UV processing for both electrodes, a large area (4 cm2) and semi-transparent flexible DSC with PCE of  4% was obtained. A comparison with standard fabrication and materials showing a clear enhancement in stability (20% PCE loss after 600 hours of light soaking at maxiumum power point instead of 100 hours) and  bending resistance (from radius= 20 mm to radius= 8 mm) of the new TiO2 formulation.  

For mesostructured perovskite solar cell, TiO2 is used both as compact layer and as mesoporous electron transport layer. We propose a screen printable TiO2 compact layer formulation, which is more suitable for scaling up compared to spray pyrolysis.  With this novel approach,  we achieved PCE up to 5.6% for small area cell and 2.7 % for series connected module.

 

Finally, nanostructuring the mesoporous TiO2 in forms of vertically aligned nanorods via hydrothermal method, we were able to enhance charge collection  and  a PCE of 12.4 % for perovskite based devices was obtained.

 

 



[1] V. Zardetto, F. Di Giacomo, D. Garcia-Alonso, W. Keuning, M. Creatore, C. Mazzuca, A. Reale, A. Di Carlo, T.M. Brown, Fully Plastic Dye Solar Cell Devices by Low-Temperature UV-Irradiation of both the Mesoporous TiO2 Photo- and Platinized Counter-Electrodes, Advanced Energy Materials, 3 (2013) 1292-1298.
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