Increased consumption of petroleum and natural gas over several decades has led to the energy shortage concern. To meet a growing need for electrical energy, solar energy which is abundant and clean, has been widely employed. Solar radiation can be directly converted to electricity using photovoltaic devices or solar cells. Depending on the types of semiconductor, solar cells can be classified into four categories that are silicon solar cells, III-V solar cells, organic solar cells and dye-sensitized solar cells. Among these solar cells, the organic solar cells have gaining attention due to the low cost of materials, light-weight, ease of fabrications and processes. However, the power conversion efficiency (PCE) and the stability of organic photovoltaics are considering low. The highest recorded efficiency of single-junction organic solar cells is 11.5 %. Therefore, improvement of the device efficiency has remained the challenge. In this review, we focused on the principle of organic photovoltaics, the recent progress of organic semiconductors, the advanced in large scaled fabrication and the future directions of organic solar cells research.