Energy transfer in CaYAlO4: Ce3+, Pr3+ for sensitization of quantum-cutting with the Pr3+-Yb3+ couple

Abstract

Silicon based solar cells show a poor yield in the UV-blue range of the solar spectrum. The thermalization of the charge carriers is one major loss mechanism, which could be overcome by depositing a quantum-cutting material in front of the solar cell. This phenomenon has recently been demonstrated in materials doped with the rare-earth couple Pr3+-Yb3+, where Pr3+ is able to sensitize two Yb3+ ion for one absorbed blue photon. Unfortunately, the weak absorption cross-section of Pr3+ ion makes it not suitable for thin films applications. Therefore, it is necessary to sensitize it to obtain a significant light yield. In that respect, Ce3+ ion could be used as a sensitizer of Pr3+ because its 4f-5d transition shows a high cross-section absorption. The purpose of this article is to study energy transfers between Ce3+ and Pr3+ in CaYAlO4 with a view to evaluate the potential of Ce3+ as a sensitizer of quantum-cutting with Pr3+-Yb3+ couple. We present results obtained in the bulk material and in a thin film deposited by pulsed laser deposition and we demonstrate that, in CaYAlO4, Ce3+ ion sensitizes the 3Pj levels of Pr3+ ion, but also that this may be followed by a cross-relaxation involving the 4f levels of Ce3+ ion, which would be in competition with energy transfer toward Yb3+ ion.

Enhanced Pr3+ photoluminescence by energy transfer in SrF2 : Eu2+, Pr3+ phosphor

“…One suggestion to investigate is to add a third sensitizer. 4,8 Eu 2+ could be used as a sensitizer because it shows a fully allowed 4f-5d transition. 9,10 This transition strongly depends on the crystal field of the matrix.…”

Efficient near-infrared quantum cutting in Yb3+ doped CaNb2O6 phosphor based on energy transfer

“…However, the incident solar spectrum is dominant in the ultraviolet (UV) to visible region. Hence, one of the attempts is to improve the solar cell efficiency by spectral modulation [1][2][3], for example, quantum cutting (QC). The process of QC, which converts one high-energy photon absorbed into two or more low-energy photons, could significantly reduce the thermalization loss [4,5].…”

Nanostructured down-converter module for photovoltaic application

“…The influence of the crystal field in the energy level of this intra-configurational transition restricts the host matrix choice. Ce 3+ in CaYAlO 4 have already shown good properties, with 4f-5d absorption band between 300 and 400nm 18 .…”

“…The role of this device is to absorb UV-blue photons and to convert them, with a multiplication phenomenon, into IR photons near the maximum of sensibility of c-Si. [17][18][19] . At this stage, the same limitation as up-conversion occurs, meaning the low absorption cross-section of the 4f-4f inter-configurational transitions.…”

“…The goal of frequency converters is to modify the solar spectrum and adapt it to the semiconductor spectral response. Two emerging concepts, based on rare-earths doped thin layer, are being considered: the up-conversion 13,14 and the down-conversion [15][16][17][18][19] processes. Up-conversion which leads after two or more photons absorption to the emission of light at shorter wavelengths, could allow for the use of photons with energy lower than the band gap.…”