The temperature dependence of photoluminescence lifetimes in a-P₂Se, a-P₃Se and c-P₄Se₃

Frequency-resolved photoluminescence (PL) spectra of a-P₂Se, a-P₃Se and c-P₄Se₃ have been measured as a function of temperature. A model involving two excited states was introduced previously to explain the observed phase shift between the modulated excitation and the mid-gap PL; the correlation of the quadrature-signal peak height with its position in frequency confirms this model and shows that a transition between these states competes with radiative recombination from the higher-energy state. Non-radiative recombination also occurs from both states and dominates the effective PL lifetime at high temperatures. At low temperatures, the height of the quadrature PL signal changes very little as the peak position shifts, indicating an increase with temperature in the radiative rate from the lower-energy state.