Novel Intense Emission-Tunable Li_1.5La_1.5WO₆:Mn⁴⁺,Nd³⁺,Yb³⁺ Material with Good Luminescence Thermal Stability for Potential Applications in c-Si Solar Cells and Plant-Cultivation Far-Red-NIR LEDs

Abstract

Novel pure Li1.5La1.5WO6:Mn4+,Nd3+,Yb3+ (LLWO:Mn4+,Nd3+,Yb3+) materials with intense emission-tunable far-red-near-infrared (far-red-NIR), potentially applied in crystalline silicon (c-Si) solar cells and plant-cultivation applications, were prepared using a high-temperature solid-state reaction approach. In optimal LLWO:0.03Mn4+, a far-red emission band peaking at 714 nm, corresponding to Mn4+ 2Eg → 4A2g transition of the 3d3 electron in a [MnO6] octahedron, is observed upon the 345 nm ultraviolet (UV) excitation. The broad excitation spectrum (λex = 714 nm) can be decomposed into four Gaussian bands centered at 323 nm (30 960 cm–1), 350 nm (28 571 cm–1), 399 nm (25 063 cm–1), and 470 nm (21 277 cm–1), respectively, which are assigned to Mn4+ ← O2– charge transfer, Mn4+ 4T1g ← 4A2g, 2T2g ← 4A2g, and 4T2g ← 4A2g transitions. When Nd3+/Yb3+ is introduced into the LLWO:0.03Mn4+ system, an energy-transfer process from Mn4+ to Nd3+/Yb3+ is demonstrated, which realizes the spectral conversion of broadband UV–visible to far-red emission and NIR. However, the energy-transfer mechanisms for them seem to be different, in which the former one intends to be a resonant process of electronic dipole–dipole interaction, whereas the latter one is proposed as a multiphonon-assisted mechanism. In the case of codoping Nd3+ and Yb3+ into LLWO:0.03Mn4+, the Yb3+ emission is enhanced based on a elucidated successive energy-transfer process of Mn4+ → Nd3+ → Yb3+. Consequently, the UV–visible light can be effectively converted into tunable NIR emission in this system based on the synergistic effect of dual Mn4+ → Nd3+ → Yb3+ and Mn4+ → Yb3+ energy-transfer processes, matching well with the high spectral response region for c-Si solar cells. Moreover, the acquired far-red-NIR emission also couples well with the absorption spectrum of biologically active states Pfr and photosynthetic bacteria, which suggests its potential application in plant-cultivation LEDs. Additionally, the good luminescence thermal stability is found in LLWO:0.03Mn4+,0.02/3Nd3+,0.05/3Yb3+, further supporting its feasibility.

NIR‐I/III afterglow induced by energy transfers between Er and Cr codoped in ZGGO nanoparticles for potential bioimaging

“…This declining trend indicates that an energy transfer from Cr 3+ to Er 3+ occurs within Cr 3+ /Er 3+ codoped ZGGO. The aforementioned result is similar as those reported by Li et al 39,40 …”

Deep‐red‐emitting SrLaLiTeO6: Mn4+ double perovskites: Correlation between Mn4+‐O2− bonding and photoluminescence

“…The emission intensity of 679, 696, and 708 nm decreases to 50, 36, and 38%, respectively, when temperature varies from 300 to 463 K. The temperature at which photoluminescence emission intensity reaches 50% of the initial intensity or thermal quenching temperature (T 50 ) is attained around 400 K. Thermal quenching mechanism of Mn 4+ ‐activated phosphors can be well explained using two models viz . nonradiative relaxation and Dorenbos's photoionization model 43–47 . According to nonradiative relaxation model, at higher temperatures electrons in the excited level get pumped to the cross point between 4 T 2g and 4 A 2g levels by absorbing activation energy (∆E) and return to the ground state via a series of nonradiative processes.…”

“…nonradiative relaxation and Dorenbos's photoionization model. [43][44][45][46][47] According to nonradiative relaxation model, at higher temperatures electrons in the excited level get pumped to the cross point between 4 T 2g and 4 A 2g levels by absorbing activation energy (∆E) and return to the ground state via a series of nonradiative processes. The thermal activation energy of the SrLaLiTeO 6 :5%Mn 4+ phosphor is calculated using Arrhenius equation given by where I 0 is the initial PL intensity, I T is the PL intensity at a given temperature T, C is a constant, and k is the Boltzmann constant (8.617 × 10 − 5 eV∕K).…”

Synthesis and characterization of a Eu3+‐activated Ba2–xV2O7:xEu3+ phosphor using a hydrothermal method: a potential material for near‐UV‐WLED applications

“…7 F 4 , this intensity was dependent on the environment, but was not hypersensitive. [19,[35][36][37][38][39][40] According to Judd-Ofelt theory, [41] the ratio of intensities (R) of electron transitions within the 4f shell of Eu 3+ ions (i.e.) R = I…”