Visible to infrared emission from (Eu³⁺/Nd³⁺):B<inf>2</inf>O<inf>3</inf> + AlF<inf>3</inf> + NaF + CaF<inf>2</inf> glasses for luminescent solar converters

Abstract

Melt quenching technique was used for the preparation of fluoroborate (BFanc:B2O3 + AlF3 + NaF + CaF2) glasses with europium (Eu3+) and neodymium (Nd3+) ions. The absorption bands of (Eu3+/Nd3+):BFanc glasses in the visible and near infrared (NIR) regions and their spectral response with the standard solar spectrum were studied. The co-operative type down conversion (DC) process was explored using a photoluminescence (PL) spectra, which can convert a blue photon (464 nm) of Eu3+ (visible) into three photons (905, 1072, and 1346 nm) of Nd3+ (NIR) ions. The decay curves for the 615 nm (5D0→7F2) emission were fitted well to the bi-exponential function in (Eu3+/Nd3+) co-activated BFanc glasses. The faster decline of lifetime with increasing Nd3+ concentration indicates the efficient energy transfer (ET) between Eu3+ and Nd3+ ions. This ET:(Eu3+ → Nd3+) upon a dipole-quadrupole interaction was confirmed by the Dexter and Reisfeld's theory. Moreover, quantum efficiency (ηQE) was calculated from the results of decay times, and achieved a maximum value of 185%. By stimulating with 464 nm, the color coordinates were significantly fallen in red region and their correlated color temperature values were calculated to be at around 1000 K. The aforementioned results suggest that (Eu3+/Nd3+):BFanc glasses could be used as the spectral convertors in silicon solar cells and efficient NIR emitters, and also for warm light sources.