Bi‐Functional Single‐Crystalline Active Layers for Uniform Area‐Emitting Organic Light‐Emitting Transistors

Organic light‐emitting transistors (OLETs) have great potential in the next‐generation display technology. However, achieving uniform emission remains a challenge. In this study, monolayer molecular crystals (MMCs) of C 5 ‐DNTT were developed as highly efficient bi‐functional active layers for area‐emitting OLETs, providing a mobility of 6.64 cm 2 V −1 s −1 , threshold voltage of −0.46 V, current on/off ratio over 10 6 , and subthreshold swing of 226 mV/dec. The C 5 ‐DNTT MMC‐based OLETs exhibit a uniform emission across the entire anode region, with the intensity difference between the two edges of the emitting area smaller than 6.8%. Compared to polycrystalline thin‐film OLETs, the C 5 ‐DNTT MMC‐based OLETs achieve a transition from typical line emission to area emission, thanks to the efficient horizontal hole transport and vertical hole injection. This work demonstrates the potential of high‐mobility MMCs as the bi‐functional hole transport and injection layers in high‐performance OLETs, offering novel insights for developing uniform area‐emitting OLETs and facilitating the application of OLETs in future displays.