[13a-N205-1~12] 12.4 Organic light-emitting devices and organic transistors

▼ [13a-N205-4] Highly oriented Lead-Free Cs₃Cu₂I₅ Single Nanocrystal Film via Gel Permeation Chromatography Purification

〇YuHong Cheng¹, Rikuo Suzuki¹, Narumi Shinotsuka¹, Hinako Ebe¹, Naoaki Oshita², Ryohei Yamakado¹, Takayuki Chiba¹, Akito Masuhara², Junji Kido¹ (1.Yamagata Univ. Org., 2.Yamagata Univ. Eng.)

Keywords:Lead-free, Single crystal, Gel permeation chromatography

The emergence of environment friendly materials has attracted considerable attention in the field of optoelectronics. Copper-based lead-free halide perovskite (with a near-unity quantum yield) obtained from Cs₃Cu₂I₅ can exhibit blue emission with a wavelength of 440 nm and provide outstanding stability for various applications. However, in practical applications, colloidal dispersion purity and film quality are still an issue to make a quality thin film for a device. In this study, an antisolvent-free gel permeation chromatography (GPC) is first used to purify lead-free Cs₃Cu₂I₅ nanocrystals (NCs). The purified Cs₃Cu₂I₅ NCs exhibit completely eliminated impurities from NMR spectra (Fig. 1). The Cs₃Cu₂I₅ NCs also exhibit a high photoluminescent quantum yield (~100% in a colloidal solution and 79.3% in a film) and provide a highly oriented single-crystal film (Fig. 2). Density functional theory (DFT) calculation results showed that the surface energy Cs₃Cu₂I₅ was the lowest at (020) owing to the high phase stability in the film. Finally, it has been demonstrated for the first time that the mixture of polymethyl methacrylate (PMMA) and Cs₃Cu₂I₅ NCs has waterproofing capabilities. The composite film consisting of Cs₃Cu₂I₅ NCs and PMMA can survive in water for at least 10 days. This result opens up more possibilities for the application of these NCs.