p-Type mesoscopic NiO as an active interfacial layer for carbon counter electrode based perovskite solar cells

Abstract

Replacement of the ZrO₂ insulator layer in the state-of-the-art TiO₂/ZrO₂/carbon structure by mesoscopic p-type NiO particles led to 39% increase of energy conversion efficiency of hole-conductor-free organometallic perovskite heterojunction solar cells with carbon counter electrodes. In these cells, the light absorber, CH₃NH₃PbI₃, formed instantly inside the pores of the entire TiO₂/NiO/carbon layer upon sequential deposition of PbI₂ and CH₃NH₃I. Photoluminescence, impedance spectroscopy and transient photovoltage decay measurements have revealed that introduction of NiO extended the electron lifetime and augmented the hole extraction of the counter electrode. As a result, the photocurrent and open-circuit voltage both increased, resulting in a cell with impressive energy conversion efficiency of 11.4% under AM1.5G conditions.