Broadband Cr^3+-sensitized upconversion luminescence in La_3Ga_5GeO_14: Cr^3+,Yb^3+,Er^3+

Abstract

Broadband-light-sensitized upconversion (UC) photon management phenomenon in La 3 Ga 5 GeO 14 :Cr 3+ ,Yb 3+ ,Er 3+ is reported, featuring the concentrated broadband noncoherent light excitable at room temperature. Energy transfer among Cr 3+ /Yb 3+ /Er 3+ in the Stokes and UC luminescence processes reveals that Yb 3+ as a "bridge" is requisite for Cr 3+ -sensitized UC luminescence of Er 3+ . Low Cr 3+ contents are preferred for UC luminescence of Yb 3+ -Er 3+ , since it would be quenched by high Cr 3+ contents. The designed UC emissions 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 of Er 3+ at around 510 ~560 nm are proposed to through Energy transfer upconversion (ETU) mechanism based on the Cr 3+ -Yb 3+ dimer model with superexchange interaction according to crystallographic data and the decay curves of Er 3+ UC emission. This research may open up a new perspective to design novel photonic materials excitable by broadband noncoherent light for improving the photoresponse of solar cells. , "Ultra-broadband near-infrared excitable upconversion core/shell nanocrystals," Chem. Commun. (Camb.) 48(47), 5898-5900 (2012). 10.

Broadband-sensitive Ni2+–Er3+ based upconverters for crystalline silicon solar cells

“…Sharp absorption peaks located at 970, 800, 660, 520, 490, 410, 380 nm and comparatively broad absorption band around (1450-1600) nm were assigned to the f-f transitions of Er 3+ ions, 24,34 while rather broad but comparatively weak absorption bands located around (1050-1500) nm, (680-860) nm and (390-460) nm were originated from the 3 A 2 ( 3 F) to 3 T 2 ( 3 F), 3 T 1 ( 3 F) and 3 T 1 ( 3 P) optically allowed transitions, respectively, of six coordinated Ni 2+ ions. 20,32 No distinct Ni 3+ absorption bands were identied indicating that most of the doped Ni stabilised as Ni 2+ ions. 25,33 We used Nb 5+ ions as charge compensator in double amount to that of doped Ni that might have stabilized the added Ni as Ni 2+ ions.…”

“…19) and similarly Cr 3+ for 600-650 nm. 20 On the other hand, upconversion with a rather broadband sensitivity and a high efficiency has been demonstrated using triplettriplet annihilation of organic molecules but the absorption range is limited up to 800 nm at present and thus can have applications only for a-Si, organic, and dye-sensitized solar cells. [21][22][23] …”

Efficient Super Broadband NIR Ca2LuZr2Al3O12:Cr3+,Yb3+ Garnet Phosphor for pc‐LED Light Source toward NIR Spectroscopy Applications

“…The pc‐LED produced the NIR light output power of 26 mW at 100 mA drive current . Actually, Cr 3+ and Yb 3+ codoped NIR phosphors have been studied mostly as spectral converters for silicon solar cells applications . For this application, the phosphors were designed to have highly efficient energy transfer from Cr 3+ to Yb 3+ , and, therefore, the dominant emission of Yb 3+ located around 1000 nm matching well the spectral response of Si solar cell.…”

BaCl2:Er3+—A High Efficient Upconversion Phosphor for Broadband Near‐Infrared Photoresponsive Devices

“…Up to now, in most of the proof‐of‐concept experiments, UC materials and their application in PV cells are commonly investigated using monochromatic lasers with high‐power densities above the limitations of solar applications . However, studies on UC materials upon excitation of incoherent broadband NIR sunlight are still absent so far . Given the nature of the sunlight that it exhibits a continuous and polychromatic spectrum, UC luminescence efficiency of RE 3+ ‐doped materials can be drastically enhanced through simultaneous multiwavelengths excitation.…”