Downconversion for solar cells in NaYF4:Er,Yb

Abstract

Downconversion is a promising avenue to boost the efficiency of solar cells by absorbing one higher energy visible photon and emitting two lower energy near-infrared ͑NIR͒ photons. Here the efficiency of downconversion for the ͑Er 3+ ,Yb 3+ ͒ couple is investigated in NaYF 4 , a well-known host lattice for efficient upconversion with ͑Er 3+ ,Yb 3+ ͒. Analysis of the excitation and emission spectra for NaYF 4 doped with 1% Er 3+ and codoped with 0%, 5%, 10%, or 30% Yb 3+ show that visible to NIR downconversion is inefficient. Downconversion by the scheme based on the reverse of the upconversion process is hampered by fast multiphonon relaxation from the 4 F 7/2 level ͑the starting level for downconversion͒ to the 4 S 3/2 level. Energy transfer from the 4 S 3/2 level of Er 3+ to Yb 3+ is shown to be inefficient. Efficient downconversion from the 4 G 11/2 of Er 3+ level is observed, resulting in emission of two photons ͑one around 980 nm and one around 650 nm͒ after absorption of a single 380 nm photon.

Photoluminescence in electronic ferroelectric Er1−xYbxFe2O4

“…5(a), fits very well with the original experimental result. Such data analysis gives a fixed energy assignment and a nearly unique combination of transitions with evenly spaced splitting, which is unlike former treatments for amorphous glasses [12][13][14] or doped crystalline materials [11,15], of which the energy assignment and number of transitions is not unique and the sub-levels are often not evenly-spaced in energy.…”

“…Most of former reports on PL of Er 3+ ions in amorphous [12][13][14] and crystalline [11,15] materials were explained by Stark splitting, of which narrow green (around 548nm) and red (around 660nm) bands were frequently observed, with an energy interval of typically 5-10 meV for the visible range. What we have observed for Er 1-x Yb x Fe 2 O 4 ( Fig.…”

A sequential two-step near-infrared quantum splitting in Ho3+ singly doped NaYF4

“…10 Most recently, NIR downconversion phenomena have been widely witnessed in the RE 3+ -Yb 3+ (RE= Tb, Pr, Tm, Nd, Er, and Ho) co-doped luminescent materials. [11][12][13][14][15][16][17][18] However, in the most of the case, the NIR emission might originate from Yb 3+ through first-order energy transfer from RE 3+ donor ions rather than QS. There is still a general lack of understanding of NIR-QS luminescence mechanisms, and very few related studies are available.…”

“…Electronic mail: qyzhang@scut.edu.cn the high photon energy side, is therefore of significant interest for various aspects. [11][12][13][14][15][16][17][18][19][20][21] In the case of splitting one UV or blue photon into two NIR photons, the Shockley-Queisser limit could be increased to 40% for a single junction Si-based solar cell. 22 In this paper, we demonstrated a sequential two-step NIR-QS in a Ho 3+ -doped β-NaYF 4 which is distinct from the aforementioned visible QS and NIR downconversion of RE 3+ -Yb 3+ .…”

Synthesis of β-Phase NaYF4:Yb,Er Upconversion Nanocrystals and Nanorods by Hot-Injection of Small Particles of the α-Phase

“…During the last years, a large number of research papers was pub-lished on the synthesis of NaREF 4 nanocrystals (RE = rare-earth), since NaREF 4 and LiREF 4 are attractive host lattices for a variety of functional optical materials such as upconversion phosphors, [6][7][8][9][10][11][12][13][14] quantum-cutting phosphors, [15][16][17][18][19] laser materials, [20,21] and materials for solar cell applications [22][23][24][25][26]. A variety of synthetic methods has been described for producing solvent-dispersible sodium rare-earth tetrafluoride nanocrystals with controlled size, shape and capping ligand, including thermal decomposition, [7,[27][28][29][30][31][32] co-precipitation, [6,11,[33][34][35][36][37][38][39][40] or solvothermal methods [41][42][43][44][45][46][47]…”