A-site cation-pseudohalide co-design for tin halide perovskite transistors.

Guanidinium thiocyanate (GuaSCN) maximizes Sn–SCN–Sn bonding and the iodine migration barrier in formamidinium tin iodide (FASnI3), enabling p-channel TFTs with mobility above 88 cm2 V−1 s−1.

• Why it matters: Tin halide perovskite electronics are limited by a fragile crystal framework, Sn2+ oxidation, and fast crystallization that undermine stability and device performance.
• What they did: Using density functional theory, the study tunes Sn–X–Sn bond strength and halide migration barriers via A-site cation size and hydrogen bonding with SCN− and I−, then tests GuaSCN in tens-of-nanometer FASnI3 films and TFTs.
• The result: GuaSCN improves crystallinity and grain size, prolongs carrier lifetimes, and suppresses Sn4+ formation without changing the intrinsic bandgap, yielding I on/off ratios above 4 × 10^9 with negligible hysteresis and strong operational and shelf stability across hundreds of devices.

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