Electrical characterization of TiO2/CH3NH3PbI3 heterojunction solar cells

Abstract

TiO₂/CH₃NH₃PbI₃ heterojunction solar cells were fabricated by spin-coating and characterized by current–voltage measurements, impedance spectroscopy and capacitance–voltage measurements. It was demonstrated that the TiO₂/CH₃NH₃PbI₃ layers form an ideal p–n heterojunction suitable for the photovoltaic applications. The active acceptor concentration of 9.67 × 10¹⁵ cm⁻³ in the CH₃NH₃PbI₃ layer and the built-in potential of 0.67 eV in the TiO₂/CH₃NH₃PbI₃ heterojunction were derived by the Mott–Schottky relationship. Numerical simulations showed that the acceptor concentration in the CH₃NH₃PbI₃ layer greatly influenced the electron potential barrier height at the junction interface. The degradation of TiO₂/CH₃NH₃PbI₃ heterojunction solar cells showed that the efficiency remained 35.5% after storage under ambient laboratory conditions for 15 days. These results indicated that the oriented TiO₂ layers provide a possible route to fabricate stable perovskite-based photovoltaic devices without hole transporting materials.