廣工大《APL》：一種”協同調控的創新策略！實現長波長寬帶近紅外發光

寬帶近紅外（NIR）熒光粉是構建下一代緊湊、高效NIR光源的核心材料，在光譜分析、生物成像、無損檢測及夜視等領域具有重大應用需求。其中，Cr3?離子因其在弱晶場中可產生源于4T2 → 4A2躍遷的寬帶發射而成為關鍵激活劑。然而，該領域長期面臨一個根本性挑戰：為實現更長波長（如> 900 nm）的發射，通常需要削弱晶場以降低4T2能級，但這會同時增強電子-聲子耦合，導致發光效率驟降和熱穩定性惡化。因此，如何突破“紅移-效率-熱穩定性”三者之間的相互制約，協同實現顯著光譜紅移、高量子效率與優異熱穩定性，是本方向亟待解決的關鍵科學問題與核心技術瓶頸。

廣東工業大學金亞洪等人報道了Cr3+摻雜的尖晶石結構材料實現長波長寬帶近紅外發光，該工作提出了一種“晶場工程”與“發光中心工程”協同調控的創新策略。具體通過在重摻Cr3+的MgGa2O4尖晶石基質中，引入大半徑In3+離子部分取代Ga3+，實現了晶格擴張與晶場強度的削弱。同時，高濃度的Cr3+摻雜促進了交換耦合Cr3+-二聚體的形成。這兩種效應協同作用，共同降低了二聚體激發態的能量，從而在保持高效輻射躍遷的前提下，將發射峰顯著紅移至940 nm。所研制的熒光粉實現了240 nm的半高寬、71.56%的內量子效率及423 K下65%的發光強度保持率。研究通過結構解析與光譜學手段，深入闡明了In3+在調制局域配位環境與穩定Cr3+-二聚體方面的雙重作用機制。最后，封裝成的熒光轉換LED器件在300 mA驅動下獲得55.71 mW的NIR輸出功率，并成功演示了其在溶液光譜檢測、皮下血管成像及穿透識別等場景的應用，驗證了該材料作為高性能寬帶NIR光源的實用潛力。

相關論文以主題“Lowering Cr3+-dimer excited states via In3+-mediated crystal field weakening in spinel: A route to long-wavelength broadband NIR luminescence”發表在Applied Physics Letters上。

論文鏈接：

https://doi.org/10.1063/5.0304465

FIG.1.(a) PXRD patterns of MG2-yIyO:0.06Cr3+(y = 0–0.12) and the corresponding magnified view in the2θ range of 35°–37°. (b) Evolution of lattice parameters and octahedralbond lengths in MG2-yIyO as a function of In3+concentration. (c) Crystal structure diagram of the MG2-yIyO solid solution. (d) SEM and elemental mapping images of MG1.9I0.1O:0.06Cr3+.

FIG. 2.(a) Excitation and (b) normalized emission spectra of MG2-yIyO:0.06Cr3+(y = 0–0.12). (c) Tanabe-Sugano diagram clarifying the crystal-field-induced redshift in Cr3+ emission. (d) Emission spectra of MG1.9I0.1O:xCr3+(x = 0.02–0.12). (e) EPR spectra of MG1.9I0.1O:xCr3+(x = 0.02 and 0.06). (f) Decay curves of MG1.9I0.1O:xCr3+(x = 0.02–0.12). (g) DR spectra of MG2-yIyO:xCr3+. (h) Configurational-coordinate scheme depicting the downward shift of Cr3+-dimer excited states.

FIG. 3. IQE, EQE, and AE of (a) MG2-yIyO:0.06Cr3+(y = 0–0.12) and (b) MG1.9I0.1O:xCr3+(x = 0.02–0.12). NIR emission intensity as a function of temperature of (c) MG2-yIyO:0.06Cr3+(y = 0–0.12) and (d) MG1.9I0.1O:xCr3+ (x = 0.02–0.12). (e) Fitted activation energies and Huang-Rhys factors for MG2-yIyO:0.06Cr3+(y = 0–0.12). (f) A schematic diagram for illustrating the thermal quenching process.

FIG. 4. (a) EL spectra of the pc-LED device at varied drive currents. Insets: photographs of the NIR pc-LED in the off and on states. (b) NIR output power and PCE versus drive current. (c) Absorption spectra of deionized water, anhydrous ethanol, and diphenyl oxide. (d)–(f) Photographs captured under daylight illumination (top) using a home used camera and under illumination by the broadband NIR pc-LED (bottom) taken with an NIR camera.

本文來自“材料科學與工程”公眾號，感謝作者團隊支持。

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