Unmanned aerial vehicles have been around for decades in the aerospace community, looking into the numerous technological and sophisticated solutions for transport alternatives, opening up new frontiers for aerial supremacy, accounting for the exponentially increasing population density. Now, UAVs accountable for their broad variation in their sizes from being minuscule up to a humungous weaponized system, primarily operate on electric systems to achieve better performance and effective payload allowances. With electricity dominating the technological race, improvising the same for sustainability requirements is also a budding area of scrutiny and research. That being well noted, solar power is another dimension of exploiting the concept of renewability and sustainability, owing to its adaptability. Hence, this work is a comprehensive, detailed review of the research that had been undertaken so far, in integrating solar power sources to unmanned aerial vehicles.