Low Threshold Voltage Lead–Tin Perovskite Transistors with Enhanced Ambient Stability

Thin-film
transistors (TFTs) based on lead–tin perovskites
have garnered significant attention for electronic applications due
to their high mobilities. However, the facile oxidation of Sn2+ to Sn4+ results in unintended doping, compromising
channel modulation and reducing on–off ratios. In this work,
we investigate the effect of A- and B-site cation engineering on TFT
performance and stability. We demonstrate an ambient-stable device
(RH > 70%, 25 °C) with a threshold voltage (Vth) of 4.7 V and an on–off ratio of ∼106, maintaining stability for over an hour without encapsulation.
This enhanced performance is attributed to substituting cesium with
the larger methylammonium cation, which suppresses Sn oxidation and
doping, as supported by XPS and Hall measurements. Such devices with
low Vth and high on–off ratios
are promising for low-power electronic circuits with reliable and
well-defined switching characteristics, highlighting the potential
of A-site tuning in perovskite TFTs.