Amino-Functionalized Conjugated Polymer Electron Transport layers Enhances UV-Photostability of Planar Heterojunction Perovskite Solar Cells
In this work, we report, for the first time, a solution-processed amino-functionalized copolymer semiconductor (PFN-2TNDI) with a conjugated backbone composed of fluorine, naphthalene diimide, and thiophene spacers as the electron transporting layer (ETL) in the n-i-p planar structured perovskite solar cells. Using this copolymer semiconductor in conjunction with a planar n-i-p heterojunction, we achieved an unprecedented efficiency of ~17% under standard illumination test conditions. More importantly, the perovskite devices using this polymer ETL have shown good stability under constant ultra violet (UV) light soaking during 3000 h of accelerated tests. Various advanced spectroscopic characterizations including ultrafast spectroscopy, ultra-violet photoelectron spectroscopy and electronic impedance spectroscopy elucidate that the interaction between the functional polymer ETL and perovskite layer plays a critical role on trap passivation, and thus the device UV-photostability. We expect these results will boost the development of low temperature solution-processed organic ETL materials, which is essential for commercialization of high-performance and stable flexible perovskite solar cells.