Sb3+ -Er3+ -Codoped Cs2 NaInCl6 for Emitting Blue and Short-Wave Infrared Radiation.

Cs2 NaInCl6 double perovskite is stable, environmentally benign and easy to prepare. But it has a wide band gap (5.1 eV), and therefore, does not show optical and optoelectronic properties in the visible and short-wave infrared (SWIR) region. Here we introduce such functionalities in Cs2 NaInCl6 by codoping Sb3+ (s-electron doping) and Er3+ (f-electron doping) ions. Sb3+ doping introduces optically allowed 5s2 → 5s1 5p1 electronic absorption at the sub-band gap level, which then emits blue photoluminescence with ≈93 % quantum yield. But f-f electronic absorption of Er3+ is parity forbidden. Codoping Sb3+ -Er3+ , leads to transfer of excitation energy from Sb3+ to Er3+ , yielding SWIR emission at 1540 nm. Temperature (6 to 300 K) dependent photoluminescence measurements elucidate the excitation and emission mechanism. A phosphor converted light emitting diode (pc-LED) fabricated by using the codoped sample emits stable blue and SWIR radiation over prolonged (84 hours) operation at 5.1 V.

Electron-phonon coupling in APd3O4: A = Ca, Sr, and Sr0.85Li0.15.

Here we have investigated the role of electron phonon coupling on the Raman spectrum of narrow bandgap semiconductors APd3O4 (A = Ca, Sr) and hole-doped system Sr0.85Li0.15Pd3O4. Four Raman active phonons are observed at room temperature for all three compounds as predicted by factor group analysis. The lowest energy phonon (∼190/202 cm-1) associated with Pd vibrations is observed to exhibit an asymmetric Fano-like lineshape in all the three compounds, indicating the presence of an interaction between the phonon and the electronic continuum. The origin of the electronic continuum states and electron-phonon coupling are discussed based on our laser power- and temperature-dependent Raman results. We have observed an enhanced strength of electron-phonon coupling in Sr0.85Li0.15Pd3O4 at low temperatures which can be attributed to the metallicity in this doped compound.