Core–shell-like Y₂O₃:[(Tb³⁺–Yb³⁺), Li⁺]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion

Abstract

Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd(1-x)Zn(x)S is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd(1-x)Zn(x)S can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln(3+)-Yb(3+) couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb(3+)-Yb(3+)), Li(+)] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb(3+)-Yb(3+) quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb(3+). Broadband down-conversion to the Yb(3+) NIR emission was obtained in a wide range of 250-650 nm.

Integrating Down-Shifting and Down-Conversion into Metal–Organic Frameworks to Enhance the Spectral Conversion for Solar Cells

“…The DCbridge effect has been mentioned in previous literature. 18 However, there has been no research quantifying the effect. Therefore, we introduce QY to explore the quantified impact.…”

“…The result indicates that Dy 3+ (or Tb 3+ ) acts as a bridge to modulate the Δ E and enhance the η ET . The DC-bridge effect has been mentioned in previous literature . However, there has been no research quantifying the effect.…”

“…Since DS and DC have complementary properties, scientists have tried to integrate those two process in the same platform to overcome the spectra mismatch and enhance the efficiency of solar cell. Up to now, this strategy have been achieved in Ce 3+ (Eu 2+ , Bi 3+ as well)/ Ln 3+ –Yb 3+ inorganic phosphor , and quantum dots/Ln 3+ –Yb 3+ inorganic phosphor heterostructure systems. , In it, Ce 3+ ions (or quantum dots), acting as harvesting media, absorb a high energy photon at first, then the energy transfer (ET) from absorber to Ln 3+ ion, finally DC processes were performed by lanthanide ion couples to split one photon into two photons. However, the η ET in DS process (absorbing media to Ln 3+ ) are low, which affects the whole spectral conversion efficiency.…”