Conjugated push-pull type oligomer as a new electron transport material for improved stability p-i-n perovskite solar cells

Push-pull type conjugated oligomer TBTBT with alternating thiophene (T) and benzothiadiazole (B) blocks was studied as an electron transport layer (ETL) material for p-i-n perovskite solar cells. The devices assembled using TBTBT as the single-component ETL provided the encouraging photovoltaic performance as reflected in the obtained power conversion efficiency (PCE) of 14.3%. The hybrid ETL structure composed of PC61BM/TBTBT bilayer increased substantially the device short circuit current density and boosted PCE from 14.3% to 17.4%. Even though the application of TBTBT as the component of hybrid ETL did not enhance the device efficiency as compared to the reference cells using PC61BM, such modification significantly improved the operational stability of PSCs, which is crucially important for practical implementation of this technology. •Conjugated oligomer TBTBT was investigated as electron transport layer (ETL) material.•Perovskite solar cells using individual TBTBT as ETL delivered efficiency of 10.5%.•Using TBTBT in combination with PC61BM improved the device efficiency to 17.8%.•Applying TBTBT as ETL enhanced the operational stability of perovskite solar cells.