Novel materials for third generation solar cells have emerged as one of the major scientific contribution in alternative energy approaches. In this scenario, semiconductor nanomaterials and organic dye molecules have greatly acknowledged for their vast contribution to the solar energy applications. Research on semiconductor nanomaterials for fabricating future generation solar cells is still fascinating due to their extraordinary structural and optical properties. Moreover, functionalization of organic dye molecules helps to harvest large amount of photons in order to apply them for high efficiency solar cell devices. Various attempts have been made to improve efficiency of quantum dot-sensitized solar cells and dye-sensitized solar cells using semiconductor inorganic nanomaterials and organic/organometallic dye molecules. Out of these, co-sensitization has been looking as most promising approach to improve the efficiency considerably. A record of over 14% of efficiency has been achieved in recent years through co-sensitization strategy. The energy transfer process during co-sensitization is also a very crucial and interesting.This review deals about materials, methods, various approaches and role of co-sensitization in enhancing the efficiency of dye-sensitized and quantum dot sensitized solar cells. The critical issues existing in the co-sensitization approach are also elaborately discussed.