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Perovskite Based Hybrid Solar Cells with Transparent Carbon Nanotube electrodes Kamil Mielczarek and Anvar A. Zakhidov Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, TX 75080, U.S.A. ABSTRACT Recently, major advances have been made in electrolytic and solid state DSSCs through the use of perovskite nanocrystals as a sensitizing agent where power conversion efficiencies of over 12% have been realized [1–3]. Moreover the planar DSSC/PV devices with perovskites used as photoactive absorbers sandwiched between selective electron and hole transport layers have demonstrated record performances. Additionally, the uses of carbon nanotubes (CNTs) as a flexible, transparent, lightweight and robust electrode material have been demonstrated in both DSSC as well as OPV devices. The application of CNTs as a charge collector with perovskite sensitized solid state planar PV and DSSCs is discussed. Performance characteristics of CNTs within perovskite based hybrid OPVs are investigated and the role of CNTs as an efficient charge collector is extended to the inverted geometry. INTRODUCTION Organic Photovoltaics (OPVs) and Dye Sensitized Solar Cells (DSSCs) have been viewed as attractive candidates for next generation sources of renewable energy. They have been coveted because of their ability to be produced in large quantitates using cost effective and well established technologies, such as roll-to-roll processing [4]. However, they have ultimately staggered to overcome their limitations. In the case of OPVs based on polymers, low mobilities and short exciton diffusion lengths have lead to single junction cells with power conversion efficiencies (PCEs) less than 10% [5]. While DSSCs have struggled to replace volatile liquid electrolytes commonly used in cells with PCEs greater than 12% [6] with solid state hole transport materials (HTMs), which have been limited to PCEs less than 10% [7,8] in solid state DSSCs (ssDSSCs). Researchers have attempted to increase the efficiencies of these technologies through the development of new absorbers with reduced band-gaps [5,6], stacked structures with multiple absorbers [9–11] and increasing the interfacial area of typically planar devices through the use of nanoengineered surfaces [12]. Initially used as a light sensitizer material in liquid electrolyte based DSSCs [13], organo-metallic halides with the perovskite crystal structure (Figure 1a) have gained steady interest from both the DSSC and OPV communities. Cells based on this class of materials have enjoyed a steady increase in power conversion efficiency from 10% in late 2012 [14] to over 15% in most recent reports [15,16] when used in a ssDSSC configuration (Figure 1b). Due to a strong absorption coefficient and extremely long diffusion length, over 100nm for CH3NH3PbI3 [17] and over 100nm for CH3NH3PbI3-xClx [18], cells based on these materials can be highly efficient without the need for a mesoporous layer. In this work we propose a structure based on the highly efficient organo-metallic perovskite