Intrinsic thermal stability of inverted perovskite solar cells based on electrochemical deposited PEDOT

Thermal stability of perovskite materials is an issue impairing the long-term operation of inverted perovskite solar cells (PSCs). Herein, the thermal attenuation mechanism of the MAPbI3 films that deposited on two different hole transport layers (HTL), poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and poly(3,4-ethylenedioxythiophene) (PEDOT), is comprehensively studied by applying a heat treatment at 85 °C. The thermal stress causes the mutual ions migration of I, Pb and Ag through the device, which leads to the thermal decomposition of perovskite to form PbI2. Interestingly, we find that I ions tend to migrate more towards electron transport layer (ETL) during heating, which is different with the observation of I ions migration towards HTL when bias pressure is applied. Moreover, the use of electrochemical deposited PEDOT as HTL significantly decreases the defect density of MAPbI3 films as compared to PEDOT:PSS supported one. The electrochemical deposition PEDOT has good carrier mobility and low acidity, which avoids the drawbacks of aqueous PEDOT:PSS. Accordingly, the inverted PSCs based on PEDOT show superior durability than that with PEDOT:PSS. Our results reveal detailed degradation routes of a new kind of inverted PSCs which can contribute to the understanding of the failure of thermal-aged inverted PSCs.