1 Supporting information A Simple Spiro Type Hole Transporting Material for Efficient Perovskite Solar Cells Paramaguru Ganesan, a† Kunwu Fu, b† Peng Gao, a* Ines Raabe, a Kurt Schenk, c Rosario Scopelliti, a Jingshan Luo, a Lydia H. Wong, b Michael Grätzel, a and Mohammad Khaja Nazeeruddin, a* † These authors contribute equally to the work. a Laboratory of Photonics and Interfaces, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Station 6, 1015 Lausanne, Switzerland. peng.gao@epfl.ch, mdkhaja.nazeeruddin@epfl.ch b Energy Research Institute@NTU (ERI@N), School of Materials Science and Engineering, Nanyang Technological University Nanyang Avenue, Singapore 637553 (Singapore) c Institut des Sciences et Ingénierie Chimiques (ISIC) and Institut de Physique des Systèmes Biologiques (IPSB), EPFL, CH-1015, Lausanne, Switzerland Electronic Supplementary Material (ESI) for Energy & Environmental Science. This journal is © The Royal Society of Chemistry 2015