Shiferaw, Tesfaye2018-07-052023-11-092018-07-052023-11-092009-06http://10.90.10.223:4000/handle/123456789/6677Visible photoluminescence from nano-silicon is one of the most attractive and debatable issue in recent years. Studying photoluminescence and understanding its mechanism has tremendous attention due to optoelectronic applications. When the size of quantum dots decreases the surface area to volume ratio increases and localized surface states appears in the forbidden region. Exciton energy states are also exists in the same gap region. It is important to examine the combined e ects of exciton, localized surface states and quantum con nement e ects. We have explicitly integrated these e ects in a phenomenological model to obtain analytical expression for the photoluminescence spectra. Initially, we explicitly calculated the exciton binding energy and we incorporate the exciton contribution then combined it with quantum con nement model and surface states to see its e ect on photoluminescence. Accordingly, we observed that taking the e ect of exciton states into account explains almost accurately the experimental photoluminescence data. The results obtained using MATLAB programming. Calculations take place at room temperature on small quantum dots (1 - 5 nm). In conclusion, our results are quite new and it re ect some of the feature that has quite close correspondence with the experimental. The results are also in conformity with other theoretical and experimental investigationsenPhenomenological ModelThesis