“…However, with the growth of ZnS, more and more defects will be created because of its polycrystalline nature. For quantification of the radiative recombination of ultraviolet emission in G-Z-S-4 and G-Z-S-6, the bimolecular rate equation of radiative recombination in a semiconductor can be used: , where R is the radiative recombination rate, n e the electron concentration, n h the hole concentration, and B the radiative recombination coefficient, whose typical values are from about 10 –11 to 10 –9 cm 3 /s for ZnO. , Since excess carriers are generated and recombined in pairs (namely, n e = n h ), eq becomes R = Bn e 2 . This equation implies that the radiative recombination rate R in each localized trap is proportional to the square of the carrier concentration, which means that the high localized carrier concentration will lead to a high radiative recombination rate and thus intensive emission.…”