The Effect Of Urea Additive On Organic-Inorganic Perovskite Solar Cells

Organic–inorganic hybrid perovskite materials have recently gained prominence as light active layers in the photovoltaic field due to their excellent properties.The perovskite thin films as active light absorption layers play a vital role in the whole perovskite solar cells.The quality of perovskite layers has great influence on the ability to light absorption and carriers transport for solar cells.Usually,perovskite layers with full coverage and large grain size are necessary to high performance perovskite solar cells.It is a challenge to grow perovskite films with large crystalline grains and a full coverage on the surface of an organic compound film by a solution process.Herein,we for the first time introduced environmental-friendly urea into PbI₂ precursor to mediate the perovskite film growth and crystallization on the top of PEODT:PSS for efficient inverted solar cells.We obtain different PbI₂ films by introducing different ratio of urea additive.Infrared spectroscopy and scanning electron microscopy images demonstrated that urea was coordinated with PbI₂ to form Pb I₂·O=C?NH₂?₂ complex,resulting in large Pb I₂ flakes by a slow crystallization.The large PbI₂ flake with fewer nucleation sites is conducive to forming monolithic perovskite grains.Further investigation found that CH3NH3I·PbI2·O=C?NH₂?₂ complex was formed as an intermediate phase,which retarded the crystallization process of the perovskite films.These factors leaded to a high-quality perovskite film with large grain size and excellent crystallinity.This enables us to fabricate the inverted perovskite solar cells showing a maximum efficiency of 18.01%with a fill factor of82.29%and a stabilized efficiency of 17.56%.