寬帶近紅外（NIR）熒光粉是構(gòu)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(wú)損檢測(cè)及夜視等領(lǐng)域具有重大應(yīng)用需求。其中，Cr3?離子因其在弱晶場(chǎng)中可產(chǎn)生源于4T2 → 4A2躍遷的寬帶發(fā)射而成為關(guān)鍵激活劑。然而，該領(lǐng)域長(zhǎng)期面臨一個(gè)根本性挑戰(zhàn)：為實(shí)現(xiàn)更長(zhǎng)波長(zhǎng)（如> 900 nm）的發(fā)射，通常需要削弱晶場(chǎng)以降低4T2能級(jí)，但這會(huì)同時(shí)增強(qiáng)電子-聲子耦合，導(dǎo)致發(fā)光效率驟降和熱穩(wěn)定性惡化。因此，如何突破“紅移-效率-熱穩(wěn)定性”三者之間的相互制約，協(xié)同實(shí)現(xiàn)顯著光譜紅移、高量子效率與優(yōu)異熱穩(wěn)定性，是本方向亟待解決的關(guān)鍵科學(xué)問(wèn)題與核心技術(shù)瓶頸。

廣東工業(yè)大學(xué)金亞洪等人報(bào)道了Cr3+摻雜的尖晶石結(jié)構(gòu)材料實(shí)現(xiàn)長(zhǎng)波長(zhǎng)寬帶近紅外發(fā)光，該工作提出了一種“晶場(chǎng)工程”與“發(fā)光中心工程”協(xié)同調(diào)控的創(chuàng)新策略。具體通過(guò)在重?fù)紺r3+的MgGa2O4尖晶石基質(zhì)中，引入大半徑In3+離子部分取代Ga3+，實(shí)現(xiàn)了晶格擴(kuò)張與晶場(chǎng)強(qiáng)度的削弱。同時(shí)，高濃度的Cr3+摻雜促進(jìn)了交換耦合Cr3+-二聚體的形成。這兩種效應(yīng)協(xié)同作用，共同降低了二聚體激發(fā)態(tài)的能量，從而在保持高效輻射躍遷的前提下，將發(fā)射峰顯著紅移至940 nm。所研制的熒光粉實(shí)現(xiàn)了240 nm的半高寬、71.56%的內(nèi)量子效率及423 K下65%的發(fā)光強(qiáng)度保持率。研究通過(guò)結(jié)構(gòu)解析與光譜學(xué)手段，深入闡明了In3+在調(diào)制局域配位環(huán)境與穩(wěn)定Cr3+-二聚體方面的雙重作用機(jī)制。最后，封裝成的熒光轉(zhuǎn)換LED器件在300 mA驅(qū)動(dòng)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(cè)、皮下血管成像及穿透識(shí)別等場(chǎng)景的應(yīng)用，驗(yàn)證了該材料作為高性能寬帶NIR光源的實(shí)用潛力。

相關(guān)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(fā)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(lái)自“材料科學(xué)與工程”公眾號(hào)，感謝作者團(tuán)隊(duì)支持。

近期學(xué)術(shù)會(huì)議推薦