Modification of Two‐Dimensional Tin‐Based Perovskites by Pentanoic Acid for Improved Performance of Field‐Effect Transistors

Abstract Understanding and controlling the nucleation and crystallization in solution‐processed perovskite thin films are critical to achieving high in‐plane charge carrier transport in field‐effect transistors (FETs). This work demonstrates a simple and effective additive engineering strategy using pentanoic acid (PA). Here, PA is introduced to both modulate the crystallization process and improve the charge carrier transport in 2D 2‐thiopheneethylammonium tin iodide ((TEA) 2 SnI 4 ) perovskite FETs. It is revealed that the carboxylic group of PA is strongly coordinated to the spacer cation TEAI and [SnI 6 ] 4− framework in the perovskite precursor solution, inducing heterogeneous nucleation and lowering undesired oxidation of Sn 2+ during the film formation. These factors contribute to a reduced defect density and improved film morphology, including lower surface roughness and larger grain size, resulting in overall enhanced transistor performance. The reduced defect density and decreased ion migration lead to a higher p‐channel charge carrier mobility of 0.7 cm 2 V −1 s −1 , which is more than a threefold increase compared with the control device. Temperature‐dependent charge transport studies demonstrate a mobility of 2.3 cm 2 V −1 s −1 at 100 K due to the diminished ion mobility at low temperatures. This result illustrates that the additive strategy bears great potential to realize high‐performance Sn‐based perovskite FETs.