Laser induced photocurrent and photovoltage transient measurements of dye-sensitized solar cells based on TiO 2 nanosheets and TiO 2 nanoparticles Hamid M. Ghaithan a , Saif M.H.[6_TD$DIFF] Qaid a , Mahmoud Hezam b,c , Joselito P. Labis b,d , [7_TD$DIFF]Mohammad Alduraibi a,e , Idriss M. Bedja f [8_TD$DIFF] , Abdullah S. Aldwayyan a, * a Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia b King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2454, Riyadh 11451, Saudi Arabia c Laboratory of Quantum Optoelectronics, Ecole Polytechnique Fédérale de Lausanne (EPFL),1015 Lausanne, Switzerland d Math-Physics Dept., Mindanao State University (MSU)-Fatima Campus, Gen. Santos City, 9500, Philippines e [10_TD$DIFF]National Center for Applied Physics, King Abdulaziz City for Science and Technology, KACST, Riyadh 11442, Saudi Arabia f Cornea Research Chair, Department of Optometry, College of Applied Medical Sciences, King Saud University,[11_TD$DIFF] Riyadh 11433, Saudi Arabia ARTICLE INFO Article history: Received 27 May 2016 Received in revised form 3 July 2016 Accepted 4 July 2016 Available online 5 July 2016 Keywords: Laser induced transient decay DSSCs TiO 2 nanosheets {001} facet [12_TD$DIFF]ABSTRACT Dye-sensitized solar cells (DSSCs) based on TiO 2 nanoparticles and TiO 2 nanosheets with exposed {001} facets are investigated using laser-induced photovoltage and photocurrent transient decay (LIPVCD) measurements. We adopted a simplified version of LIPVCD technique, in which a single illumination light source and a laboratory oscilloscope could be conveniently used for the measurements. Although the {001} surface of TiO 2 nanosheets allowed a noticeably slower recombination with the electrolyte, this was counterpoised by a slower electron transport probably due to its planar morphology, resulting in a shorter diffusion length in TiO 2 nanosheets. The nanosheet morphology also resulted in less surface area and therefore reduced short circuit current density in the fabricated devices. Our work highlights the fact that the morphological parameters of TiO 2 nanosheets finally resulting after electrode film deposition is of no less importance than the reported efficient dye adsorption and slow electron recombination at the surface of individual nanosheets. ã 2016 Elsevier Ltd. All rights reserved. 1. Introduction Dye-sensitized solar [13_TD$DIFF]cells (DSSCs) have been widely studied in the past two decades, due to [14_TD$DIFF]their low cost and high efficiency [15_TD$DIFF] among third generation photovoltaic [16_TD$DIFF]technologies [1,2]. A typical DSSC consists of a dye-sensitized semiconductor electrode, a counter electrode and a redox electrolyte. Under illumination, electrons generated by photo-excited dye molecules are injected into the conduction band of the semiconductor film and trans- ported from the injection sites to the contact electrode. Finally, electrons are collected and pass through the external load. Meanwhile, the oxidized dye molecules are regenerated by the redox couple (I  =I  3 ) in the electrolyte [3,4]. The operation of a DSSC depends on several reactions that occur at interfaces between different materials [4]. In particular, the process of electron injection at the TiO 2 /dye interface and the electron recombination reaction at the TiO 2 /dye/electrolyte interface are critical because they control both the short circuit current and open circuit voltage of the DSSC. The surface properties of the TiO 2 material play an important role in both processes [4,5]. The process of electron recombination is dominated by the interaction between [17_TD$DIFF]electrons at the surface of TiO 2 and I  3 ions in the electrolyte [5]. Generally, TiO 2 nanostructures used in DSSCs have anatase phase structure with mostly {101} exposed facets, due to the strong stability of this surface as compared to other crystal facets [4,6]. The different surface properties of the {001} and {101} facets of TiO 2 are expected to have a profound effect on the chemicophysical processes in DSSCs. Maitani et al. [1] reported a significant improvement of electron transfer process at the dye-{001} surface compared to the {101} facet. As a result, TiO 2 nanosheets with exposed {001} surfaces are promising candidate to improve light harvesting in DSSCs [7]. Few reports have emerged on DSSCs based on nanosheets, with fewer discussing the electron transport dynamics in nanosheet-based DSSCs [2,8]. * Corresponding author. E-mail address: [9_TD$DIFF]dwayyan@ksu.edu.sa (A.S. Aldwayyan). http://dx.doi.org/10.1016/j.electacta.2016.07.021 0013-4686/ã 2016 Elsevier Ltd. All rights reserved. Electrochimica Acta 212 (2016) 992–997 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta