Molecular Engineering of 2D Organic–Inorganic Hybrid Perovskites for Room-Temperature Warm-White Light Phosphorescence

Developing room-temperature phosphorescence (RTP) in organic-inorganic hybrid perovskites (OIHPs) with color tunability is an attractive topic for investigating how the coupling between organic and inorganic components affects spin-orbital effects and triplet state energy transfer. We demonstrate that the modulation of organic spacer cations in the OIHPs can effectively realize tunable white-light RTP. By gradually substituting the 2-phenylethylamine (PEA) cations in (PEA)2PbBr4 with naphthalene-type organic cations (N-naphthyl methylamine, NMA), triplet excitons can be extracted from the inorganic part and transferred to the organic part to produce a tunable RTP. In particular, the OIHP crystal with stoichiometry (PEA)0.8(NMA)1.2PbBr4 leads to warm-white light phosphorescence due to the contribution from additional ultraviolet absorption, which was then exploited to fabricate a phosphorescent warm-white light LED. A similar approach was also applied to 1-pyrenemethylamine (PRMA) cations. By controlling the content ratio between the PRMA and PEA molecules, colorful phosphorescence emissions were realized in (PEA)x(PRMA)2-xPbBr4 (0 ≤ x ≤ 2). The phosphorescence lifetimes of (PEA)0.8(NMA)1.2PbBr4 and (PEA)1.4(PRMA)0.6PbBr4 are 3.18 ms at 473 nm and 3.02 ms at 618 nm, respectively. Our results provide an effective strategy for synthesizing multicolor phosphorescent perovskites by tuning the ratio of different organic fluorophore molecules.