Highly efficient photoelectron emission from stable low-work-function surfaces using organic bases

Photocathodes coated with alkali metals such as cesium (Cs) exhibit high quantum efficiency (QE) owing to their low work functions (WFs). However, their poor stability and short lifetimes under vacuum conditions limit their practical application. In this study, we demonstrate that modifying electrodes with phenanthroline derivatives allows to achieve ultra-low WFs of 2.2 eV while significantly enhancing their stability compared to Cs under both high vacuum (∼10−5 Pa) and ultra-high vacuum (∼10−8 Pa) conditions. Notably, 4,7-bis(1-pyrrolidinyl)-1,10-phenanthroline exhibited greater stability than Cs and achieved more than twice the QE of Cs in the 2.7–3.5 eV photon energy range, without relying on negative electron affinity structures. These findings demonstrate the potential of organic low-WF materials as alternatives to alkali metals for photocathode applications, offering extended photoemission lifetimes under less stringent vacuum conditions.