Stable and Efficient Green Perovskite Nanocrystal–Polysilazane Films for White LEDs Using an Electrospray Deposition Process

• Published in: ACS applied materials & interfaces 2019-06, Vol.11 (25), p.22510-22520
• Main Authors: Yoon, Hee Chang, Do, Young Rag
• Format: Article
• Language: English
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.9b04164

We successfully fabricated a stable, efficient, and easy-to-use CsPbBr3 perovskite nanocrystal (PeNC)-embedded inorganic polymer film through an encapsulation step with a Si–N/Si–O-based polysilazane (PSZ) matrix via the electrospray (e-spray) deposition of a silazane (SZ) oligomer-decorated PeNC solution. To eliminate Pb2+ defect sites that are generated when the ligands are peeled from the PeNC surface, surface passivation of the Lewis acid/base adduct is possible by coupling the SZ oligomer (the donor of lone pairs) with Pb2+ sites (the acceptor of lone pairs). With the addition of the SZ oligomer, the photoluminescence quantum yield of photodegraded CsPbBr3 PeNC was recovered and increased by 2.35-fold whereas the stability was improved significantly from an untreated CsPbBr3 PeNC solution. During the e-spray deposition process, SZ-treated CsPbBr3 PeNC solution droplets can react with atmospheric moisture to polymerize and form a Si–N/Si–O network encapsulant via a sol–gel reaction. The resultant CsPbBr3–PSZ films showed improved stability levels under most environmental conditions, including air storage, blue light exposure, UV exposure, thermal exposure, and water immersion. The optimum CsPbBr3–PSZ film-covered blue light-emitting diode (LED) showed good performance capabilities, with a luminous efficacy (LE) of 85.9 lm/W and color-by-blue conversion efficiency (CE) of 60.1%. Furthermore, this easy-to-use CsPbBr3–PSZ film can be employed to realize a remote-type white-by-blue LED by combining it with red emissive K2SiF6:Mn4+/silicone film. The LE and CE rates of the white LED were 71.0 lm/W and 50.8%, respectively, at a correlated color temperature of 9334 K, with only an 8% drop in the LE for long-term operation of 100 h. This result indicates that e-spray deposition is a simple fabrication process by which to create stable and efficient PeNC films from an unstable PeNC solution using a rapid sol–gel reaction between droplets and moisture from the air.