Electrides for electronic devices: From demonstrated applications to emerging concepts

An electride is a compound in which electrons confined within crystallographic voids act as anions. Interest in electrides has grown steadily since the discovery of room-temperature-stable [Ca₂₄Al₂₈O₆₄]⁴⁺(4e⁻) (C12A7:e⁻) in 2003, although subsequent research has focused predominantly on heterogeneous catalysis. This mini-review shifts the focus to electronic and optoelectronic devices, critically examining which applications have been experimentally demonstrated, how their performance compares with that of established technologies, and why many theoretically proposed devices remain unrealized. Vacuum and plasma electron sources represent the most mature application domain. Heaterless hollow cathodes incorporating C12A7:e⁻ inserts can ignite at room temperature and operate continuously for more than 950 h, while plasma-activated C12A7:e⁻ converter grids increase the extracted negative hydrogen ion (H⁻) beam current by 70% without the use of cesium. Thin-film optoelectronics constitute a second experimentally validated domain: a 4 nm amorphous C12A7:e⁻ electron-injection layer deposited by room-temperature sputtering reduces the turn-on voltage of an inverted organic light-emitting diode from 9.2 to 4.7 V. In contrast, barrier-free Ohmic contacts to two-dimensional semiconductors, spintronic injectors, and devices based on topological electrides remain largely at the computational proposal stage. By comparing experimentally measured device figures of merit with relevant materials benchmarks, this review also examines from an apparent field-emission barrier of 0.6 eV to a surface work function near 5.0 eV for a single compound and discusses the factors underlying this apparent disparity. We argue that the principal obstacle to broader device integration is not a lack of promising intrinsic electronic properties, but the chemical instability of many electrides under device-processing and operating conditions. Accordingly, future efforts should pursue two complementary directions: process optimization, contact engineering, and reliability assessment for electrides already demonstrated in functional devices; and the targeted discovery and integration of chemically robust electrides for applications inaccessible to more reactive compounds.