Enhancement of silicon solar cells by downshifting with Eu and Tb coordination complexes

Abstract

Luminescent lanthanide‐doped oxides, nanoparticles, nanocrystals, and coordination complexes are major tools in the fields of optical and laser materials, telecommunications, medical imaging, and fluoroimmunoassays. In particular, coordination complexes are efficient energy converters with high photostability, large ligand‐induced Stokes shifts, and tunable excitation and emission spectra. However, their application as light downshifting materials for solar cells has not yet been widely explored. This third generation solar cell concept enables to increase the efficiency of standard solar cells—such as Si or copper indium gallium (di)selenide (CIGS)—that have low performance for ultraviolet photons. The incorporation of such a converter in solar module encapsulants can provide a cheap and effective way to integrate photon conversion. Here, encapsulants functionalised by photon downshifting coordination complexes have been spin‐coated on silicon solar cells. For all the coordination complexes, an increase of the spectral response of the solar cells is observed in the ultraviolet region. In the best case, a relative increase of 8% of the conversion efficiency of the solar cell is observed. Copyright © 2016 John Wiley & Sons, Ltd.

Lanthanide-based downshifting layers tested in a solar car race

“…These results are very promising and among the highest values reported for Ln 3+ -based LDS coatings 19,42 mentioned in Table 1, except for the case of a LDS layer based on Eu(tta) 3 2H 2 O complex with 4,5-bis(pinene)-2,2'bipyridine ligand dispersed in polyvinyl acetate (PVA), which presented an absolute EQE increase of 50% 13 . To illustrate the concept of enhancing PV cells performance using LDS coatings, the PV-2 devices were coupled to a wheeled structure composing a small solar vehicle, and a race between solar vehicles with bare and coated PV-2 devices was performed in horizontal plane ( Fig.…”

“…where  1 and  2 are the limits of the spectral overlap between the absorption spectrum of dU6-Tb and tU5-Eu and the AM1.5G spectrum, AM1.5G Φ is the AM1.5G photon flux and A is the absorbance of tU5-Eu and dU6-Tb. A value of 8.8×10 18 photons•s −1 •m −2 was found for dU6-Tb and for tU5-Eu, the value was 6.8×10 19…”

“…The reasons for the wide utilization of Ln 3+ complexes (europium, Eu 3+ , and terbium, Tb 3+ ) are related to their strong emission and photostability and also the emission profile in the visible spectral range, which overlaps the absorption of c-Si solar cells. Moreover, Eu 3+ and Tb 3+ based materials display significantly larger ligands-induced Stokes shifts, when compared to organic dyes or QDs, minimizing the losses by self-absorption 19 .…”

Energy Transfer in Supramolecular Heteronuclear Lanthanide Dimers and Application to Fluoride Sensing in Water

“…F D represents the luminescence quantumy ield (QY) of the Tb donor in the absence of an acceptor, N A the Avogadro number, and n is the refractiove index of the mediumi nE quation (3), whereas q DA represents the angles between the electric dipoles of the donor (D) and acceptor (A)a nd q D and q A represent the angles between the dipoleso ft he donor and acceptorw ith the straight line containing Da nd A, respectively,i nE quation (4). Considering that the excited-state lifetime of the Ln atoms are very long lived (i.e.,m s), it is generallya ssumed that the orientation of the donor and acceptord ipolesa re randomized within the excited-state lifetimes ot hat the average k 2 value is 2/3.…”

“…Lanthanide-basedphotonic devices are finding numerous applicationsi no ur daily life, such as phosphors, [1] lasers, [2] or luminescent bioassays. [3] The abilityt oc ontrol the photon flux in Ln devices is of upmosti mportancet of unnel the energy at the expected outcome level, such as for downshifting materials appliedt ot he optimization of solar cells [4] or for efficientbiolabeling that targets the optical biological window. [5] Similarly, control of the energy-transfer pathways betweenexcitedl evels is ac ornerstone of Ln-based upconverting devices.U pconversion (UC) allows for the conversion of low-energyp hotons into high-energyp hotons.…”