Development of high-efficiency photoluminescent silica glasses of dense aggregates of photoactive centers

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H02802
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 36010:Inorganic compounds and inorganic materials chemistry-related
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: Kajihara Koichi 東京都立大学, 都市環境科学研究科, 教授 (90293927)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: シリカガラス / 光活性中心凝集体 / 希土類イオン / エネルギー移動 / ナノ結晶

Outline of Final Research Achievements

The aggregation of photoactive centers like rare-earth ions usually leads to a decrease in emission efficiency. This phenomenon is commonly known as "concentration quenching," and prevents to increase the concentration of photoactive centers in many solid-state phosphors. On the other hand, if quenching centers are absent, emission quenching may not occur even in the dense aggregates of photoactive centers. Based on this idea, silica glasses containing dense aggregates of rare-earth ions were employed in developing high-efficiency phosphors that utilize energy transfer. Silica-REPO4 transparent glass-ceramics that contain nanocrystals of rare-earth orthophosphates with diameters of ~5-10 nm provided unique opportunities to realize concentration-quenching-free visible or ultraviolet phosphors with internal quantum efficiencies close to unity, in which free energy migration and high efficiency emission coexist.

Free Research Field

無機材料科学

Academic Significance and Societal Importance of the Research Achievements

「濃度消光」という表現は学術用語として広く使われており、光活性中心が凝集すると必ず発光効率が下がるような印象を与えている。これに対し、本研究では、「濃度」と「消光」は必然関係にはなく、消光中心をなくすことで濃度消光を回避できる場合があることを実証した。シリカガラスは優れた透明性、強い光・放射線・化学腐食に対する耐久性、光ファイバーなどへの自由な成形性を兼備したガラスであることから、本研究で得られた知見は特に過酷環境下やエネルギー変換で使用できる堅牢な高効率透明発光材料の開発に有用であると期待される。