High‐CRI White Organic Light‐Emitting Transistors with Ultrathin Emissive Layers for Full‐Color Display

Organic light‐emitting transistors (OLETs) have attracted increasing interest as promising multifunctional three‐terminal optoelectronic devices for next‐generation active‐matrix flat‐panel displays. The development of high color rendering index (CRI) white OLETs is essential for full‐color display applications demanding excellent color fidelity. However, it remains challenging with the conventional approach of doping multiple guest emitters into a host matrix, requiring precise control needed over doping concentrations. Herein, a strategy is presented to fabricate high‐CRI white OLETs using ultrathin emissive layers (UEMLs). This approach enables simple fabrication and efficient exciton management through 2D energy transfer across adjacent layers. The integrated OLET architecture uniquely combines electrical switching with high‐quality white light emission. The resulting devices incorporating thickness‐optimized yellow and red UEMLs exhibit uniform area emission with a low turn‐on voltage below 6 V and a CRI exceeding 90. These are amongst the best performance values reported to date for ultrathin non‐doped electroluminescent devices. Furthermore, a 12 × 20 OLET pixel array is fabricated and employed as a planar backlight, enabling a color gamut coverage of 117% of the national television standards committee (NTSC) standard and vivid full‐color image display. This work provides a promising pathway for scalable, high‐quality full‐color OLET displays.