The development of photovoltaic devices, solar cells, plays a key role in renewable energy sources. Semiconductor colloidal quantum dots (CQDs), including lead chacolgenide CQDs that have tunable electronic bandgaps from infrared to visible, serve as good candidates to harvest the broad spectrum of sunlight. CQDs can be processed from solution, allowing them to be deposited in a roll-to-roll printing process compatible with low-cost fabrication of large area solar panels. Enhanced multiexciton generation process in CQD, compared with bulk semiconductors, enables the potential of exceeding Shockley-Queisser limit in CQD photovoltaics. For these advantages, CQDs photovoltaics attract great attention in academics, and extensive research works accelerate the development of CQD based solar cells. The record efficiency of CQD solar cells increased from 5.1% in 2011 to 9.9% in 2015. The improvement relies on optimized material processing, device architecture and various efforts to improve carrier collection efficiency. In this review, we have summarized the progress of CQD photovoltaics in year 2012 and after. Here we focused on the theoretical and experimental works that improve the understanding of the device physics in CQD solar cells, which may guide the development of CQD photovoltaics within the research community.