Perovskite nanocrystals are promising luminescent materials with synthetic feasibility and band gap tunability. Nonetheless, application of the perovskite nanocrystals to light-emitting devices has been challenging because of the intrinsic poor colloidal stability and environmental vulnerability issues. Here, we introduce a new protocol for highly air-stable perovskite nanocrystal layers with a tunable band gap via a simple nanocrystal pinning process. The nanocrystals were composed of CH3NH3PbBr3 (MAPbBr3) mixed with (vinylbenzylamine)2PbBr4 ((VBzA)2PbBr4), which contains a photopolymerizable structure-directing ligand. Along with the compostion of (VBzA)2PbBr4, the band gap of the perovskite layer continuously increased with the reduction of the nanocrystal size and also lattice distortion. The nanocrystal film readily polymerized upon exposure to visible light was highly stable under humid air more than 15 days. Its application to bluish-green light-emitting diodes is demonstrated.

We investigated the influence of heavy halogen atoms (Br and I) on xanthene dyes for polymerization based on visible-light photoredox initiation. Since the heavy atoms directly affect intersystem crossing (ISC), which can act as a gatekeeper in the photoredox cycle and which was expected to also affect intermolecular photoinduced electron transfer (PET), we attempted to quantify the influence of the halogens. Six different xanthene dyes were chosen based on the number and types of heavy atoms on the xanthene ring. Thus, the photopolymerization degree clearly increased in the following order: fluorescein < 4′,5′-dibromofluorescein ≤ 2′,4′,5′,7′-tetrabromofluorescein < 2′,4′,5′,7′-tetraiodofluorescein. Furthermore, 4′,5′-dibromorhodamine 6G showed a drastic enhancement in the photopolymerization degree, compared with rhodamine 6G. Therefore, we concluded that the presence of halogens on the xanthene ring increases the photoredox initiating performance due to the enhanced ISC efficiency and PET rate.

We report on the use of photoinitiated reversible addition–fragmentation chain transfer (RAFT) polymerization for the facile fabrication of cross-linked nanoporous polymer films with three-dimensionally (3D) continuous pore structure. The photoinitiated polymerization of isobornyl acrylate (IBA) in the presence of 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (CTA) and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator proceeded in a controlled manner, yet more rapidly compared to thermally initiated polymerization. When polylactide-macroCTA (PLA-CTA) was used, PLA-b-PIBA with high molar mass was obtained after several minutes of irradiation at room temperature. We confirmed that microphase separation occurs in the PLA-b-PIBA and that nanoporous PIBA can be derived from the PLA-b-PIBA precursor by selective PLA etching. To fabricate the cross-linked nanoporous polymer, IBA was copolymerized with ethylene glycol diacrylate (EGDA) in the presence of PLA-CTA to produce a cross-linked block polymer precursor consisting of bicontinuous PLA and P(IBA-co-EGDA) microdomains, via polymerization-induced microphase separation. We demonstrated that nanoporous P(IBA-co-EGDA) monoliths and films with 3D continuous pores can be readily obtained via this approach.