Metal halide perovskites, such as MAPbX 3 (X = Cl, Br, or I) have recently garnered tremendous research efforts for a broad range of photovoltaic and optoelectronic applications, [1][2][3][4][5][6][7] due to their favorable optical and electronic properties such as tunable bandgap, [2] high absorption coefficient, [3] and high photoluminescence quantum yield. [4] In particular, the power-conversion efficiencies of perovskite solar cells have been boosted to over 23% (certified) from a starting point of 3.8% over the past few years. [4][5][6][7][8] Apart from the rapid developments of materials and device architectures, a thorough understanding of fundamental physical processes including charge-carrier transport will be needed for further breakthroughs in device performance. However, a comprehensive physical picture of the intrinsic charge transport in the metal halide perovskites, which is key Optoelectronic devices based on metal halide perovskites, including solar cells and light-emitting diodes, have attracted tremendous research attention globally in the last decade. Due to their potential to achieve high carrier mobilities, organic-inorganic hybrid perovskite materials can enable high-performance, solution-processed field-effect transistors (FETs) for next-generation, low-cost, flexible electronic circuits and displays. However, the performance of perovskite FETs is hampered predominantly by device instabilities, whose origin remains poorly understood. Here, perovskite single-crystal FETs based on methylammonium lead bromide are studied and device instabilities due to electrochemical reactions at the interface between the perovskite and gold source-drain top contacts are investigated. Despite forming the contacts by a gentle, soft lamination method, evidence is found that even at such "ideal" interfaces, a defective, intermixed layer is formed at the interface upon biasing of the device. Using a bottom-contact, bottom-gate architecture, it is shown that it is possible to minimize such a reaction through a chemical modification of the electrodes, and this enables fabrication of perovskite single-crystal FETs with high mobility of up to ≈15 cm 2 V −1 s −1 at 80 K. This work addresses one of the key challenges toward the realization of high-performance solution-processed perovskite FETs.
Field-Effect Transistors
