New strategy for designing orangish-red-emitting phosphor via oxygen-vacancy-induced electronic localization

Abstract

Phosphor-converted white-light-emitting diodes (pc-WLED) have been extensively employed as solid-state lighting sources, which have a very important role in people’s daily lives. However, due to the scarcity of the red component, it is difficult to realize warm white light efficiently. Hence, red-emitting phosphors are urgently required for improving the illumination quality. In this work, we develop a novel orangish-red La4GeO8:Bi3+ phosphor, the emission peak of which is located at 600 nm under near-ultraviolet (n-UV) light excitation. The full width at half maximum (fwhm) is 103 nm, the internal quantum efficiency (IQE) exceeds 88%, and the external quantum efficiency (EQE) is 69%. According to Rietveld refinement analysis and density functional theory (DFT) calculations, Bi3+ ions randomly occupy all La sites in orthorhombic La4GeO8. Importantly, the oxygen-vacancy-induced electronic localization around the Bi3+ ions is the main reason for the highly efficient orangish-red luminescence. These results provide a new perspective and insight from the local electron structure for designing inorganic phosphor materials that realize the unique luminescence performance of Bi3+ ions.

Tuning the Bi3+-photoemission color over the entire visible region by manipulating secondary cations modulation in the ScVxP1−xO4:Bi3+ (0 ≤ x ≤ 1) solid solution

“…As for the Eu 2+ , Ce 3+ , and Mn 2+ ions, however, one major drawback is the evitable light re-absorption problem in the visible spectral region. Over the past years, a number of works had pointed out the necessity of solving this problem [22,[30][31][32][33][34][35][36][37], but it seems that the d-f (i.e., for Eu 2+ , and Ce 3+ ) and 4…”

“…., for Mn 2+ ) transitions feature an inherently-inviolable law, making them impossible to have the tunable-emission and non-visible re-absorption at the same time. By contrast, a dopant like Bi 3+ ion could be relevant to address well this point [22,32,[35][36].…”

“…Because of a naked 6s electron in the electronic configuration of [Xe]-4f 14 5d 10 6s 2 [22,[32][33][35][36][37][38], the Bi 3+ ion, depending on the specific crystal host it built into, can present the emissions broadly spanning from the UV [39], blue [40], yellow [41] and to reddish/red region [35,[32][33]42], which are analogous to the Eu 2+ , Ce 3+ , and Mn 2+ ions. As compared to the frequently reported Eu 2+ , Ce 3+ , and Mn 2+ tunable solid solutions, however, only a very limited examples of Bi 3+ emission solid solutions have been reported in the literatures, such as (Yx,Luy,Scz)VO4:Bi 3+ (yellow → reddish/red) [22], Ba3-xSrxSc4O9:Bi 3+ (blue → green) [43], and YPxV1-xO4:Bi 3+ (blue → yellow) [44].…”

A novel green‐emitting luminescent materials with broad‐band emission for high‐quality warm white LED indoor lighting

“…In addition, the DRS can be in accordance with the excitation spectrum of 0.10 Ce 3+ doped CGHAO. The band gap ( E g ) of CGHAO can be obtained by the following equations: 31‐32 where R refers to the obtained reflection in DRS, and F ( R ) and A are the Kubella‐Munk function and constant, respectively, while the incident photo energy is substituted by hυ . As shown in the right bottom corner inset of Figure 4, by making tangent to F ( R ) = 0, the obtained value of CGHAO band gap is approximately 5.56 eV.…”

An orange‐emitting phosphor BaSrGa4O8:Bi3+,K+ with unique one‐dimensional chain structure for high index color WLEDs

“…Recently, Li et al reported a new method that oxygen vacancy can induce energy level splitting of Bi 3+ ion to achieve long-wavelength emission. 7 In this work, from the viewpoint of crystal structure, we successfully realized the long-wavelength emission of Bi 3+ ions under NUV excitation. The proposed phosphor presents one-dimensional chain structure of cations along a certain crystal direction, as a result, creating abundant oxygen vacancies during high temperature sintering.…”