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Six new mixed-ligand bimetallic complexes [Eu2(bz)4(tta)2(phen)2] (1), [Gd2(bz)4(tta)2(phen)2] (2), [EuTb(bz)4(tta)2(phen)2] (3), [EuGd(bz)4(tta)2(phen)2] (4), [Eu1,2Gd0,8(bz)4(tta)2(phen)2] (5) and [Eu1,6Gd0,4(bz)4(tta)2(phen)2] (6) have been prepared with the Eu3+, Gd3+ and Tb3+ ions and the benzoate (bz−), 2-thenoyltrifluoroacetonate (tta−) and the 1,10-phenanthroline (phen) ligands. The compounds combine highly efficient antennas to obtain highly luminescent complexes to enhance solar cell efficiency. The benzoate ligand has been chosen to take its advantage as a bridging ligand to end up with bimetallic complexes to study the effect of combining two metal ions in the luminescent molecule. The structure of 1 was obtained by single-crystal X-ray diffraction, and 1–6 were found to be isostructural by powder X-ray diffraction analysis. The photophysical properties were studied by the absorbance and emission spectra and emission lifetimes. The magnetic properties of 2 were studied, and we found intramolecular antiferromagnetic interactions between the Gd3+ ions. We prepared luminescent down-shifting layers (LDSL) with the 1, 3–6 complexes embedded in ethylene–vinyl–acetate and studied their effect in the external quantum efficiency (EQE) and intensity–voltage (I–V) plots of a solar mini-module. We found that LDSL containing the bimetallic complexes 3 and 6 enhance the efficiency of the solar mini-module from 11.26(3)% to 11.76(4)% (+0.52%) and to 11.44(2)% (+0.21%), respectively. [ABSTRACT FROM AUTHOR]

In this work, we propose an alternative and fully experimental procedure based only on external quantum efficiency (EQE) measurements for characterizing the efficiency and transmittance of downshifters placed on photovoltaic (PV) devices. The experimental setup requires two PV devices as references, one of them showing a zero EQE in the downshifting spectral range. Therefore, the results obtained are independent of the quantum efficiency of the device, easing the analysis and comparison between experimental results. Also, this method avoids complex theoretical modeling proposed in other works. Those theoretical models are usually based on approximations and/or that require some input parameters difficult to determine without a wide range of experimental equipment in the lab. [ABSTRACT FROM AUTHOR]

In this work, the ageing of [Eu(bphen)(tta) 3 ]/PMMA down-shifters (DS) placed on top of photovoltaic (PV) modules exposed to extreme outdoor conditions is reported for first time. The PV modules have been placed in a defined location in Tenerife, Canary Island, where extreme outdoor conditions exist. The [Eu(bphen)(tta) 3 ]/ PMMA DSs have been directly exposed to the outdoor conditions or covered with a low iron glass. The results reveal an improvement of the total power of the modules with [Eu(bphen)(tta) 3 ]/PMMA down-shifters, 7.06% for the DS directly exposed to outdoor conditions, and a 3.95% for the encapsulated DS during the first operation day, in comparison with a reference module. However, the improvement vanishes after 20 days when the DS is not encapsulated. [ABSTRACT FROM AUTHOR]

In this work, the external quantum efficiency (EQE) of [Eu(bta) 3 me-phen] downshifters (DS) encapsulated by industrial procedures on photovoltaic (PV) modules is presented. The samples have been laminated using the DS layers faced-up and faced-down. The results obtained for the DS layers present an EQE enhancement of 1.2 % for the faced-up samples and 0.8 % for the faced-down samples. A climate chamber was used to evaluate the EQE performance during the ageing process; a temperature of 22 °C and relative humidity of 30 % was fixed. Several time cycles have been used to achieve a total UV dose of 454.94 kWh. After a 136.51 kWh dose, the increment of the EQE for the faced-up samples vanishes. In contrast, after a dose of 454.94 kWh, the EQE enhancement for samples with the DS layer faced down remains unaltered. [ABSTRACT FROM AUTHOR]

This paper reports the chemical and optical characterization of a cost effective down-converter polymeric film based on an Eu(III) complex embedded in polymethylmethacrylate (PMMA) which placed on conventional photovoltaic (PV) glass, used for module assembly, produces an increase in the external quantum efficiency (EQE) of a reference Si-based solar cell. Our results show that the best location of the down-converter is on the front surface of the glass. The UV absorption of the down-converter protects and enhances the stability of the PMMA film. This increase in EQE is further enlarged by placing a light trap on the device, collecting most of the down-converted photons, which are isotropically emitted. Additional increases in EQE are expected after a proper encapsulation of the solar cell and the glass. Thermogravimetric measurements show that the down-converter active specie is stable up to 275 °C and the PMMA film is stable up to 225 °C, consequently, it can be applied in any step of the lamination process in the production of PV modules. Thereby, the down-converter can be profitably applied in Si-based solar cells and modules, particularly in concentrated PV systems. [ABSTRACT FROM AUTHOR]

• First study of EQE by DS encapsulated on PV modules by standard industrial procedures. • Standard mc-Si module used to avoid any influence of the intrinsic solar cell EQE. • EQE improvement also attributed to reduction of DS photons scattered out of the cell. • Encapsulation reduces the degradation of luminescent properties due to UV radiation. For the first time to our knowledge, a study about the increase in external quantum efficiency (EQE) by down-shifters (DS) encapsulated by industrial procedures on photovoltaic (PV) modules is presented. EQE improves substantially in the UV range not only because of the optical path optimization for photons reaching the solar cell, but also it is attributed to the substantial reduction of DS photons scattered out of the solar cell when the outermost surface of the DS layer is embedded in ethyl-vinyl-acetate. Consequently, a proper encapsulation of DS layers is required for the optimal characterization of EQE. Moreover, the encapsulation of the DS layer substantially reduces the degradation of its luminescent properties due to UV radiation. However, the reduction of the EQE under UV radiation for the encapsulated DS layer is still high and should be substantially reduced for the integration of down-shifting properties in the lamination process of PV modules. [ABSTRACT FROM AUTHOR]