Progress in Electron-Transport Materials for Application at Perovskite Solar cells

Ever since the first organic-inorganic hybrid halogen perovskite solar cell had been first used as a photo-voltaic material in 2009, reports on this type of solar cell have grown exponentially over the years. Up till May 2014, the photo-energy conversion efficiency of the perovskite solar cell had already achieved efficiency approaching 20%. Surpassing the efficiency achieved by organic and dye synthesized solar cell, perovskite solar cell is in good hope of reaching the efficiency compatible to that of mono-crystalline silica solar cell, which makes it the star in photo-voltaic industry. Within the perovskite solar cell, the film-formation and electron-mobility of the electron transfer layer can dramatically affect its efficiency and life-span. Especially in the up-right structured device, the mesoscopic structures of the electron-transfer layer will directly influence the growth of the perovskite layer. The present researches of electron transport materials mainly focus on three aspects: 1. How to improve the instability in mesoporous TiO2-mesosuperstructured solar cells arising from light-induced desorption of surface-adsorbed oxygen. 2. How to obtain TiO2 or other electron transport materials in low temperature (sub 150 oC) in order to applicate in flexible devices. 3. Substitute mesoporous TiO2 or compact TiO2 transport layer by organic or composite materials. This article will assort the electron-transfer layer into three distinct groups according to the chemical component of the material: metal oxides, organic small molecules and composite materials, thoroughly introducing the role and the recent development of the electron-transfer material in the perovskite solar cell.