A solar cell or photovoltaic cell is a device which generates electricity directly from visible light. However, their efficiency is fairly low. So, the solar cell costs expensive according to other energy resources products. Several factors affect solar cell efficiency. In this concern, the proposed work presents the most important factors that affecting efficiency of solar cells. These effects are cell temperature, MPPT (maximum power point tracking) and energy conversion efficiency. The changing of these factors improves solar cell efficiency for more reliable applications. On the other hand, some other factors can really degrade the PV-efficiency from which are:- Solar irradiations,- Ultra-violet irradiation,- Humidity,- Snow and wind,- Hail,- High temperature,- Human settlements,- Sand and the smaller form dusts,- Some types of gases.