Even though the excited state lifetimes can be found out experimentally using well-known time-resolved spectroscopy but low signal to noise ratio leading to lack of data points on the hyperbolic curves makes it difficult to clearly reproduce the individual exponentials simply by fitting to further analyse the decay curves. Keeping these things in mind, in this work, time-resolved photoluminescent emission decay curves were simulated for aluminium doped zinc oxide [ZnO:Al (0.1–3.0%)] nanophosphors and europium doped cadmium-zinc sulphide [Cd_1−xZn_xS:Eu (0.01–10.00%, x = 0–0.5)] nanocomposite phosphor using FORTRAN-77 subroutines for three different lifetimes. Excited state lifetime is the most important parameter of nanophosphors to investigate for the purpose of opto-electronic applications, among emission intensity and wavelength. Experimentally obtained excited state lifetimes were used as the primary input to study the effect of various parameters like cut-off intensity, dopant concentration and nanocomposite composition on the decay nature of emission intensities from individual excited states, and the decay nature of total emission intensity. Decay curves generated for the ZnO:Al (0.1–3.0%) nanophosphors displayed the lifetime shortening and enhanced emission due to increasing Al-doping at all simulated arbitrary intensities for all excited state lifetimes. Decay curves generated for the Cd_1−xZn_xS:Eu (0.01–10.00%, x = 0–0.5) nanocomposite phosphors similarly displayed the trend of lifetime shortening with increasing Zn-concentration and Eu-doping for every individually simulated exponential.