Enhancing the performance of photovoltaic cells by using down-converting KCaGd（PO_4）_2：Eu~（3＋） phosphors

The goal of this work is aimed to improve the power conversion efficiency of single crystalline silicon-based photovoltaic (PV) cells by using the solar spectral conversion principle, which employed a down-converting phosphor to convert a high-energy ultraviolet photon to the less energetic red-emitting photons to improve the spectral response of Si solar cells. In this study, the surface of silicon solar cells was coated with a red-emitting KCaGd(PO4)2:Eu3+ phosphor by using the screen-printing technique. In addition to the investigation on the microstructure using scanning electron microscopy (SEM), we measured the short circuit current (Isc), open circuit voltage (Voc), and power conversion efficiency (η) of spectral-conversion cells and compared with those of bare solar cells as a reference. Preliminary experimental results revealed that in an optimized PV cell, an enhancement of (0.64+0.01)% (from 16.03% to 16.67%) in Δη of a Si-based PV cell was achieved.     

Investigations into thermoluminescence and afterglow characterization of strontium aluminates with boron-modification and reductions via sol-gel route

The effects of strontium aluminates of SrAl2O4:Eu2+,Dy3+(SAED) and boron-modified SAED (BSAED) phases synthesized from a sol-gel process on thermoluminescence (TL) along with their afterglow properties were systematically investigated with thermal activation in the different atmospheres. The result showed that the addition of boron and the reduction routes of Eu3+to Eu2+ in SrAl2O4:Dy3+were related to phosphorescent decay properties. The aid of Dy3+to induce the hole-trapping effect required both SAED and BSAED to be heated at 1300°C under the H2/N2(5%:95%) atmosphere. However, the trapping behavior of the reductions of SAED in nitrogen was similar to the compound without Dy3+co-doping SrAl2O4:Eu2+ (SAE) in H2/N2(5%:95%). BSAED showed deeper traps in situ compared to SAED which contained no boron, and this led to the better afterglow properties of BSAED than those of SAED. The afterglow spectrum of BSAED showed two peaks at 400±1 nm and 485±1 nm, which were two individuals composed and contributed from different depths of traps at 0.57 and 0.76eV, accordingly. The depth of the traps was calculated from the Hoogenstraaten’s plot of glow curves. The calculations for SAED and SAE were at around 0.43 and 0.18eV, respectively.     

Improvement of conversion efficiency of silicon solar cells using up-conversion molybdate La_2Mo_2O_9：Yb,R （R=Er, Ho） phosphors

The goal of this work was aimed to improve the power conversion efficiency of single crystalline silicon-based photovoltaic cells by using the solar spectral conversion principle, which employs an up-conversion phosphor to convert a low energy infrared photon to the more energetic visible photons to improve the spectral response. In this study, the surface of multicrystalline silicon solar cells was coated with an up-conversion molybdate phosphor to improve the spectral response of the solar cell in the near-infrared spectral range. The short circuit current (Isc), open circuit voltage (Voc), and conversion efficiency (η) of spectral conversion cells were measured. Preliminary experimental results revealed that the light conversion efficiency of a 1.5%-2.7% increase in Si-based cell was achieved.