High-Performance P-Channel Tin Halide Perovskite Thin Film Transistor Utilizing a 2D-3D Core-Shell Structure

Metal halide perovskites (MHPs) are plausible candidates for practical p-type semiconductors. However, in thin film transistor (TFT) applications, both 2D PEA₂ SnI₄ and 3D FASnI₃ MHPs have different drawbacks. In 2D MHP, the TFT mobility is seriously reduced by grain-boundary issues, whereas 3D MHP has an uncontrollably high hole density, which results in quite a large threshold voltage (V_th ). To overcome these problems, a new concept based on a 2D-3D core-shell structure is herein proposed. In the proposed structure, a 3D MHP core is fully isolated by a 2D MHP, providing two desirable effects as follows. (i) V_th can be independently controlled by the 2D component, and (ii) the grain-boundary resistance is significantly improved by the 2D/3D interface. Moreover, SnF₂ additives are used, and they facilitate the formation of the 2D/3D core-shell structure. Consequently, a high-performance p-type Sn-based MHP TFT with a field-effect mobility of ≈25 cm² V^-1 s^-1 is obtained. The voltage gain of a complementary metal oxide semiconductor (CMOS) inverter comprising an n-channel InGaZnO_x TFT and a p-channel Sn-MHP TFT is ≈200 V/V at V_DD = 20 V. Overall, the proposed 2D/3D core-shell structure is expected to provide a new route for obtaining high-performance MHP TFTs.