We report an organic lamellar single crystal as a versatile optoelectronic material in optical pumping and light-emitting transistors. The styrene derivative crystals with intrinsically ordered stacking structures, low impurities, and high photoluminescence efficiency offer a low threshold energy of 21 μJ cm −2 for amplified spontaneous emission and extraordinary device performance in terms of a striking external quantum efficiency of 3.63%, far exceeding the benchmark value in this field.

The sheet-liked organic semiconductor crystals with two-dimensional (2D) packed structures play an essential role in practical applications of high-property optoelectronic devices. Here, we reported a practical example in combination with...

Organic light‐emitting transistors (OLETs) have attracted increasing attention because of their potential applications in next‐generation displays and high‐energy operating devices. However, the simultaneous achievement of high luminescent efficiency and carrier mobility in organic semiconductors remains challenging because the localized excitons are advantageous for light emission, whereas the delocalized carriers are beneficial for efficient charge migration. Herein, we report an organic single crystal of a cyano‐substituted styrene derivative with balanced mobility yielding a record‐high external quantum efficiency of 20.5% in OLETs. Temperature‐dependent I–V curves and electronic structure analyses based on first‐principles calculations were performed to disclose the underlying mechanism as a band transport, which provides an efficient way to achieve high quantum efficiency in OLETs.