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

Metal halide perovskites are versatile materials which have already demonstrated exceptional performance in diverse optoelectronic devices. The progress has been significant; however, the fundamental understanding of the physics of charge injection remains elusive, impeding further advancements. Here, we use field-effect transistors (FETs) to investigate the impact of surface functionalization on the charge injection and transport in thin films of phenethylammonium tin iodide (PEA₂SnI₄). We show that self-assembled monolayers (SAMs) can both assist in reducing the Schottky barrier and act as an ion blocking layer between the contact and the perovskite film, limiting interfacial chemical reactions. Consequently, the contact resistance is lowered by more than 3 times compared to untreated contacts. The temperature dependence of the charge carrier mobility is discussed considering the contributions from the channel and contacts, respectively. Our results provide a quantitative framework for the charge injection in metal halide perovskites and will contribute toward the progress of high-performance optoelectronic devices including solar cells, light-emitting diodes, as well as X-ray and photodetectors.