Enhancing efficiency of perovskite solar cell via surface microstructuring: Superior grain growth and light harvesting effect Mukta C. Tathavadekar a,b , Shruti A. Agarkar a,b , Onkar S. Game a,b , Umesh P. Bansode a,b , Sneha A. Kulkarni c , Subodh G. Mhaisalkar c,⇑ , Satishchandra B. Ogale a,b,⇑ a Center of Excellence in Solar Energy, Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008, India b Academy of Scientific and Innovative Research, Anusandhan Bhawan and Network Institute of Solar Energy (CSIR-NISE), New Delhi, India c Energy Research Institute, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore Received 25 June 2014; received in revised form 30 October 2014; accepted 16 November 2014 Communicated by: Associate Editor Hari Mohan Upadhyaya Abstract We have introduced a novel approach to enhance the perovskite solar cell efficiency by controlling the grain growth and light har- vesting properties of perovskite crystallites. Instead of using a mesoporous TiO 2 layer, we have modified the surface microstructuring of the TiO 2 film by dispensing nano assembled TiO 2 submicron structures (nanobeads, NBs) on TiO 2 compact layer. With this new approach solar cell efficiency was improved significantly through an increase in both J sc and V oc . This high efficiency is attributed to crystallite size of the perovskite phase. These also act as light scattering centers giving higher current density and reduced recombination effects giving higher open circuit voltage. Ó 2014 Elsevier Ltd. All rights reserved. Keywords: Perovskite solar cells; TiO 2 nanobeads; Grain growth; Light harvesting 1. Introduction The discovery of Dye Sensitized Solar Cells (DSSCs) in 1991 by Gra ¨tzel and co-workers was a crucial break- through in the world of photovoltaics (O’Regan and Gra ¨tzel, 1991). Significant collective efforts on various sen- sitizers (Mathew et al., 2014; Gao et al., 2008), co-adsorb- ers (Allegrucci et al., 2009), co-sensitizers (Kuang et al., 2007), new counter electrodes (Zhang et al., 2012; Tathavadekar et al., 2014), new redox electrolytes (Feldt et al., 2010), etc. over the past 20 years have not only pushed the efficiencies higher but have also brought out several new ways of making robust and durable DSSCs. A significant component of this research has focused on the use of different inorganic oxide morphologies like hier- archical spheres (Liao et al., 2011; Koo et al., 2008), meso- porous nanobeads (Sauvage et al., 2010; Archana et al., 2013; Yang et al., 2010; Chen et al., 2009), nanofibers (Chuangchote et al., 2008; Shengyuan et al., 2011; Naphade et al., 2014), etc. to enhance the efficiency by tak- ing advantage of the high surface area and enhanced light scattering abilities. High DSSC conversion efficiencies using spherical morphologies are reported by Koo et al. http://dx.doi.org/10.1016/j.solener.2014.11.016 0038-092X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors. E-mail addresses: subodh@ntu.edu.sg (S.G. Mhaisalkar), sb.oga- le@ncl.res.in (S.B. Ogale). www.elsevier.com/locate/solener Available online at www.sciencedirect.com ScienceDirect Solar Energy 112 (2015) 12–19