A Study on Contact Resistance as a Function of Surface Treatment in Perovskite Field-Effect Transistors

Metal halide perovskites are versatile materials whichhave alreadydemonstrated exceptional performance in diverse optoelectronic devices.The progress has been significant; however, the fundamental understandingof the physics of charge injection remains elusive, impeding furtheradvancements. Here, we use field-effect transistors (FETs) to investigatethe impact of surface functionalization on the charge injection andtransport in thin films of phenethylammonium tin iodide (PEA(2)SnI(4)). We show that self-assembled monolayers (SAMs) canboth assist in reducing the Schottky barrier and act as an ion blockinglayer between the contact and the perovskite film, limiting interfacialchemical reactions. Consequently, the contact resistance is loweredby more than 3 times compared to untreated contacts. The temperaturedependence of the charge carrier mobility is discussed consideringthe contributions from the channel and contacts, respectively. Ourresults provide a quantitative framework for the charge injectionin metal halide perovskites and will contribute toward the progressof high-performance optoelectronic devices including solar cells,light-emitting diodes, as well as X-ray and photodetectors.