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Incorporating substitutional elements from groups I, II and IV is an important approach to improve the quality of kesterite thin films. Among the elements, Ag and Ge are most effective in promoting the performance of Cu2ZnSn(S,Se)4 solar cells. Although several theoretical and experimental studies have been conducted on the Ag/Ge-alloyed kesterite, there are significant differences in the reported morphological characteristics, photovoltaic performance and even the optimal Ag/Ge substitution ratio due to different preparation processes utilized, which leads to difficulties in comparing the Ag-incorporated and Ge-incorporated kesterite solar cells. Currently, there is little literature on the comparative study concerned. Herein, we fabricated Ag-alloyed and Ge-alloyed kesterite solar cells based on the same solution method and process conditions, and laterally compared the effects of Ag substitution and Ge substitution on the phase compositions, morphologies, optical bandgaps, minority carrier lifetime and device performance of kesterite Cu2ZnSn(S,Se)4 thin films. [ABSTRACT FROM AUTHOR]

Quasi-zero-dimensional quantum dots (QDs) have garnered significant attention owing to their distinct structural attributes, quantum confinement behaviors, optoelectronic characteristics, etc. Regrettably, their susceptibility to stability poses a challenge. In this context, leveraging rational component regulation and crystallization process optimization strategies, we presented the successful preparation of CdS QDs silicate glass through the amalgamation of melt-quenching and controlled crystallization. The optical and morphological analysis substantiated the accomplishment of in-situ precipitation of CdS QDs within the glass matrix, with grain sizes <20 nm. Integrating CdS QDs into an inorganic glass matrix remarkably augmented its fluorescence thermal stability, enabling the preservation of 85.1 % of the room-temperature luminescent intensity even at an elevated temperature of 150 °C. Moreover, the encapsulated W-LED device by near-UV LED chip, CdS QDs glass, and BaMgAl 10 O 17 :Eu2+ phosphor exhibited a warm white-light emission characterized by suitable chromaticity coordinates (0.3741, 0.3452) and a notably high color rendering index (CRI = 93). Ultimately, the radioluminescence behavior of CdS QDs glass was unveiled by utilizing it as the scintillator wafer in an X-ray imaging system, which clearly demonstrated the structure of spring encapsulated within an opaque capsule. In a nutshell, these demonstrations unequivocally emphasize the substantial potential merits of CdS QDs glass, particularly in the domains of long-term W-LED lighting and X-ray imaging applications. [ABSTRACT FROM AUTHOR]

Rare earth activated color converted phosphors have been widely used in solid-state lighting and display fields. Developing phosphors with high luminous efficiency is of great significance for light-emitting devices. Concentration quenching is the main factor limiting the improvement of phosphor luminescence efficiency during increasing the activator doping level. In this study, a novel structural optimization strategy is developed to overcome the impact of concentration quenching. In Tb3+ activated NaYSiO 4 (NYSO), large-size Gd3+ ions are introduced to adjust the distance of rare earth ions and suppress the energy transfer between Tb3+ luminescent centers. It is shown that at a critical Tb3+ concentration, for which concentration quenching tends to occur in NaYSiO 4 :Tb3+, Gd3+ incorporation successfully raises the internal quantum efficiency from 64.8 % for Tb3+-singly-doped NYSO up to 80.6 % for Gd3+/Tb3+ co-doped one. The findings can offer a feasible pathway in promoting the luminescent properties of silicate phosphor hosts. [ABSTRACT FROM AUTHOR]

Oxyfluoride glass-ceramics have become a focal point of recent research, positioned to advance significantly in areas such as LED illumination and optical data storage, etc. This study successfully prepared Pr3+-doped fluorosilicate glass and glass-ceramics embedded Na 5 Y 9 F 32 nanocrystals. The introduction of Pr 2 O 3 into the glass matrix disturbs the network structure, leading to a reduction in the band gap from 3.66 eV to 3.42 eV. When subjected to 443 nm light excitation, the 1.0 mol% Pr3+-doped glass-ceramics crystallized at 690 °C for 1.0 h exhibit the most potent luminescence, displaying seven emission peaks resulting from the radiative transition of Pr3+ ions, manifesting yellowish-pink hues. Furthermore, when stimulated by a 450 nm LD, the glass-ceramics display a distinct emission peak at approximately ∼247 nm, attributed to the electron transitions of 4 f 5 d → 3H 4 for Pr3+ ions. The luminescent properties of these glass-ceramics embedded with Na 5 Y 9 F 32 nanocrystals illustrate potential applications in up-conversion and down-conversion luminescence. • A novel Pr3+ doped SiO 2 –Al 2 O 3 –Na 2 O-NaF-YF 3 glass-ceramics was successfully prepared. • Glass-ceramics containing Na 5 Y 9 F 32 crystals exhibit efficient excitation under blue light. • The glass-ceramics exhibit yellowish-pink hues excited by 443 nm light. • The glass-ceramics presents impressive emission peaks at ∼247 nm excited by 450 nm LD. • The work stresses glass-ceramics' huge potential in up-/down-conversion luminescence. [ABSTRACT FROM AUTHOR]

Luminescent glass-ceramics has garnered significant attention within the research community owing to its exceptional characteristics, including robust chemical stability, outstanding thermal stability, and efficient thermal conductivity. However, persistent challenges include issues related to suboptimal luminous efficiency and color rendering index. In the context of this research endeavor, we have achieved a noteworthy achievement by successfully fabricating a novel variant of glass-ceramics doped with both Eu2+ and Eu3+ ions within the Na 2 O-CaO-SiO 2 system glass. This innovative glass-ceramics composition encompassed Na 4 Ca 4 Si 6 O 18 crystals, characterized by grain sizes <110 nm. Our investigations, featuring comprehensive optical spectra analysis and detailed morphological examinations, have provided substantial evidence indicating the preferential occupation of Eu3+ ions in the Ca2+ sites residing within the Na 4 Ca 4 Si 6 O 18 crystal lattice, conversely, it is possible that the distribution of Eu2+ ions occurred within the glass matrix. Additionally, it is worth noting that this glass-ceramic material demonstrated a heightened excitation efficiency when subjected to 464 nm blue light, surpassing its performance with 393 nm violet light. Detailed fluorescence spectral analysis unveiled the impressive internal quantum efficiency of the glass-ceramics, reaching an impressive 80.27%, and this glass-ceramics exhibited remarkable fluorescence thermal stability at 150 °C, preserving approximately ∼75% of its luminescent intensity at room temperature. Furthermore, we have encapsulated the white light-emitting diode (W-LED) device, integrated with a 460 nm LED chip, optimized glass-ceramics, and YAG: Ce3+ phosphor. The outcomes were characterized by the warm white-light emission, suitable chromaticity coordinates, a high color rendering index (approximately 85.4), and impressive luminous efficiency (up to 112.47 lm/W). In summary, these findings unequivocally underscore the substantial potential of glass-ceramics in the realm of high-power W-LED lighting applications. • A novel Eu3+/Eu2+ co-doped Na 2 O-CaO-SiO 2 glass-ceramics was successfully prepared. • Glass-ceramics containing Na 4 Ca 4 Si 6 O 18 crystals exhibit efficient excitation under blue light. • The glass-ceramics presents impressive IQE (80.27%) and excellent thermal stability. • The encapsulated W-LED device exhibits high CRI, and impressive luminous efficiency. • The work emphasizes the huge potential of glass-ceramics in high-power W-LED lighting. [ABSTRACT FROM AUTHOR]

Cation doping is an important approach to improve the performance of kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) thin film solar cells. Since different cation dopant has different effects on the defects and crystallization of CZTSSe absorber, it is expected to achieve better device performance via the synergistic effects of double cation co-doping compared with the single cation doping. Herein, we investigated the effects of Ag/Ge co-doping on CZTSSe solar cells by doping Ge in an already optimized Ag-alloyed CZTSSe (ACZTSSe). It is found that incorporating a small amount of Ge can further improve the crystallinity and minority carrier lifetime of ACZTSSe. The low-temperature photoluminescence results reveal that the Ge doping primarily suppressed the Sn Zn defects in ACZTSSe, thereby further boosting the device performance. However, higher Ge doping concentration can lead to a discontinuous surface morphology, which is believed to be related with the relatively low melting temperature and double-layered structure of ACZTSSe absorber. The deteriorated surface morphology results in photocurrent loss in the near-infrared region and decreased fill factor. As the Ge doping ratio increases, there is a balance between the defects and morphology. A champion power conversion efficiency (PCE), 11.4%, was achieved for the Ag/Ge co-doped CZTSSe solar cells at Ge substitution rate of 3%. Compared with the single Ag doping, the average PCE was further promoted by 0.5% due to Ag/Ge co-doping. • Ge doping can further improve the crystallinity and TRPL lifetime of ACZTSSe. • Ge doping primarily suppresses the Sn Zn defects of ACZTSSe. • Ge doping in ACZTSSe leads to discontinuous surface morphology. • Better device performance was achieved by Ag/Ge co-doping. [ABSTRACT FROM AUTHOR]

Large open-circuit voltage deficit is still the main factor restricting the performance of kesterite Cu 2 ZnSn(S,Se) 4 thin film solar cells. The high concentration of Cu Zn defects and [2Cu Zn + Sn Zn ] defect clusters are believed to be the significant origins of severe band tailing of the kesterite absorber. A promising way to improve the open-circuit voltage and power conversion efficiency of the device is substituting Ag+ with a larger ionic radius for Cu+ to suppress the defects and construct a front-graded bandgap. However, the Ag doping in kesterite can significantly lower the melting temperature, which results in difficulties in forming an Ag grading distribution across the absorber due to the strong thermal diffusion. Herein, we innovatively introduce a ZnO insert layer in the precursor film, which is expected to slow down the Ag-Cu interdiffusion during the selenization, thereby forming a desired front-graded bandgap. The Ag grading distribution in absorbers is regulated by the thickness of ZnO insert layer. The effects of ZnO insert layer on the phase compositions, morphologies, optical properties, and photovoltaic performance of Ag-doped kesterite absorbers are investigated. [ABSTRACT FROM AUTHOR]