Toward 100% coverage pure red perovskite light-emitting diodes through regulated crystallization and defect passivation of perovskite emitter films

High Efficiency Pure Red PeLEDs was demonstrated by dual passivation technique using octylammonium iodide with CIE coverage of 99.9%. • Bright pure-red PeLEDs achieved via OAI-based dual passivation ( L = 1274.9 cd m −2 and EQE = 16.47 %). • The dual-passivated devices also exhibited exceptional operational stability, maintaining a half-lifetime exceeding 9 h. • This dual passivation strategy enabled pure-red PeLEDs to emit electroluminescence at 649 nm, achieving an excellent color gamut coverage of 99.9 % in the Rec. 2020. In this study, regulated crystallization and defect passivation of red emitting perovskite films are achieved by introducing a dual-functional octylammonium iodide (OA) additive. The incorporation of OAI governs the crystallization dynamics, suppressing uncontrolled grain growth and minimizing the formation of deleterious grain boundaries. Concurrently, OAI effectively passivates ionic and surface defects within the perovskite lattice, as validated by comprehensive optoelectronic and morphological analyses. This synergistic approach combining regulated crystallization and defect passivation yields compact, uniform perovskite films with suppressed non-radiative recombination and enhanced charge transport. The resultant PeLEDs achieve pure red emission, delivering a maximum brightness (EL Max ) of 1274.9 cd m −2 , a peak external quantum efficiency (EQE Max ) of 16.47 %, and a low turn-on voltage (V on ) of 1.59 V, representing a 3.1-fold and 5.1-fold enhancement in EL Max and EQE Max , respectively, over the pristine device (409.6 cd m −2 and 3.26 %). The EL emission of the optimized device with dual OAI achieve pure red emission peak (649 nm) than the control device (666 nm), falling in excellent gamut coverage ratio of 99.9 % in Rec.2020 standard. Furthermore, the OAI-optimized devices exhibit exceptional operational stability, maintaining spectral purity under prolonged operation and achieving a half-lifetime exceeding 9 h, a 4-fold improvement compared to control devices. This work underscores the critical role of crystallization regulation and defect engineering in unlocking the full potential of perovskite emitters, offering a straightforward pathway toward efficient, stable, and color-pure PeLEDs for display applications.