Highly efficient low temperature solution processable planar type CH3NH3PbI3 perovskite flexible solar cells

Abstract

The current density–voltage (J–V) hysteresis and power conversion efficiency (η) of planar type CH₃NH₃PbI₃ perovskite solar cells with TiO₂ and ZnO electron conductors, which are formed by high temperature spray pyrolysis deposition at 450 °C and by room temperature spin-coating and subsequent heat-treatment at 150 °C, respectively, were compared. The ZnO based perovskite solar cells exhibited better efficiency deviation (15.96 ± 1.07%) and less J–V hysteresis than the TiO₂ based cells (15.20 ± 1.23%) because the ZnO based cell has 1.2 fold longer charge carrier life time (τ_n) than the ZnO based cell and the ZnO electron conductor has better electron conductivity (0.0031 mS cm⁻¹) than the TiO₂ electron conductor (0.00006 mS cm⁻¹), thereby balancing the electron flux and the hole flux more. Due to the low temperature solution processability of the ZnO electron conductor, we could demonstrate a highly efficient PEN (poly-ethylenenaphthalate)/ITO/ZnO/CH₃NH₃PbI₃ perovskite/PTAA/Au flexible planar solar cell with 1.1 V open-circuit voltage (V_oc), 18.7 short-circuit current density (mA cm⁻²) J_sc, 75% fill factor (FF), and 15.4% η for the forward scan direction and 1.1 V V_oc, 18.7 mA cm⁻²J_sc, 76% FF and 15.6% η for the reverse scan direction under illumination of 1 Sun.