Molecular N-Type Doping Unlocks Low-Threshold Nanosecond Lasing in a Microcavity-Integrated OLED Toward Electrically Pumped Organic Lasers.

Organic semiconductors are attractive for the development of flexible, wavelength-tunable lasers. However, most reported organic micro/nanolasers rely on femtosecond-pulsed optical pumping, which is impractical for real-world applications. This limitation has urged the pursuit of electrically pumped organic lasers; yet their realization remains a long-standing challenge primarily due to a fundamental materials dilemma, in which high-gain organic semiconductors often suffer from poor, unbalanced charge transport. Here, we demonstrate that this intrinsic trade-off can be effectively alleviated through a molecular doping strategy. Employing a high-gain spirofluorene derivative as the emissive layer, we introduce an n-type doped layer to construct an organic light-emitting diode (OLED), achieving more balanced charge transport while preserving outstanding optical gain. Consequently, singlet-polaron annihilation is significantly suppressed, as evidenced by reduced efficiency roll-off and electrically pumped transient absorption measurements. When integrated with a distributed feedback (DFB) resonator, the resulting device exhibits ultra-narrow (∼2 nm) electroluminescence under pulsed current injections and delivers low-threshold nanosecond lasing under an optical-electrical co-pumping configuration, thereby demonstrating a practical architecture for implementing organic laser diodes. Our work provides a general strategy to overcome the intrinsic paradox where high-gain organic semiconductors struggle to maintain balanced charge transport, illuminating a pathway toward light amplification under electrical excitation.