Hole-transport material variation in fully vacuum deposited perovskite solar cells

Abstract

This work addresses the effect of energy level alignment between the holetransporting material and the active layer in vacuum deposited, planar-heterojunction CH3NH3PbIx-3Cl x perovskite solar cells. Through a series of hole-transport materials, with conductivity values set using controlled p-doping of the layer, we correlate their ionization potentials with the open-circuit voltage of the device.With ionization potentials beyond 5.3 eV, a substantial decrease in both current density and voltage is observed, which highlights the delicate energetic balance between driving force for hole-extraction and maximizing the photovoltage. In contrast, when an optimal ionization potential match is found, the open-circuit voltage can be maximized, leading to power conversion efficiencies of up to 10.9%. These values are obtained with hole-transport materials that differ from the commonly used Spiro-MeO-TAD and correspond to a 40% performance increase versus this reference. © 2014 Author(s).