EL emission enhancement in powder electroluminescent device via insertion of receptive layer

• Published in: Electronics letters 2020-02, Vol.56 (3), p.144-147
• Main Authors: Takeda, N, Tsuneyasu, S, Satoh, T
• Format: Article
• Language: English
• Subjects: brightness; current luminance; device capacitance; device efficiency; dielectric loss; dielectric losses; EL emission enhancement; EL properties; electrical energy losses; electrodes; electroluminescence; electroluminescent devices; emission‐enhancement mechanism; frequency dependence; letter substrate; loss tangent tan; Organic and inorganic circuits and devices; permittivity; powder EL devices; powder electroluminescent device; powders; receptive layer; transparent electrode; uniform electric field
• ISSN: 0013-5194; 1350-911X; 1350-911X
• DOI: 10.1049/el.2019.3085

A method to enhance the electroluminescence (EL) of powder electroluminescent devices via the insertion of a receptive layer between the letter substrate and the transparent electrode is proposed. This approach affords uniformity of distance between the substrate and electrode, which ensures a more uniform electric field on application of a voltage to the device. Both the current and luminance are observed to increase, and the device capacitance and capacitive reactance improve on introduction of the receptive layer, which enhances the EL properties. The emission-enhancement mechanism is examined via measurements of the frequency dependence of the current, luminance, and loss tangent tan δ. Regardless of the receptive layer, the current decreases in the frequency regime over which tan δ increases, which indicates that the EL properties are affected by electrical energy losses due to dielectric loss. The frequency-dependence behaviours of tan δ and temperature are found to be different because of heat production due to both dielectric loss and radiationless deactivation, which means that dielectric loss must be reduced to improve device efficiency. Their approach can form an integral aspect of the evaluation of powder electroluminescent devices.