title: Hole-Transport Materials for Perovskite Solar Cells.
abstract: The pressure to move towards renewable energy has inspired researchers to look for ideas in photovoltaics that may lead to a major breakthrough. Recently the use of perovskites as a light harvester has lead to stunning progress. The power conversion efficiency of perovskite solar cells is now approaching parity (>22 %) with that of the established technology which took decades to reach this level of performance. The use of a hole transport material (HTM) remains indispensable in perovskite solar cells. Perovskites can conduct holes, but they are present at low levels, and for efficient charge extraction a HTM layer is a prerequisite. Herein we provide an overview of the diverse types of HTM available, from organic to inorganic, in the hope of encouraging further research and the optimization of these materials.
authors.affiliation: Abengoa Research, Abengoa, C/ Energía Solar no. 1, Campus Palmas Altas-, 41014, Sevilla, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Calió
authors.affiliation: Abengoa Research, Abengoa, C/ Energía Solar no. 1, Campus Palmas Altas-, 41014, Sevilla, Spain.
authors.forename: Samrana
authors.initials: S
authors.lastname: Kazim
authors.affiliation: Laboratory of Photonics and Interfaces, Department of Chemistry and Chemical Engineering, Swiss Federal Institute of Technology, Station 6, CH-1015, Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.affiliation: Abengoa Research, Abengoa, C/ Energía Solar no. 1, Campus Palmas Altas-, 41014, Sevilla, Spain.
authors.forename: Shahzada
authors.initials: S
authors.lastname: Ahmad
keywords: hole-transport materials; optoelectrical properties; p-type materials; perovskite solar cells; photovoltaics