Intensely pulsed white light (IPWL) treatment was tested as an ultrafast, large-area processable optical technique for the control of the nanostructure of a polymeric bulk-heterojunction photoactive layer to improve the efficiencies of polymer solar cells. Only 2 s of IPWL irradiation of a polymer:fullerene photoactive layer under ambient conditions was found to enhance significantly the power conversion efficiencies of the tested polymer solar cells to values approaching that of typical devices treated with thermal annealing. Consecutive white-light pulses from the xenon lamp induce the self-organization of the polymeric donor into an ordered structure and result in the optimized phase segregation of the polymeric donor and the fullerene acceptor in the photoactive layer, which enhances the light absorption and hole mobility and results in efficient photocurrent generation. The effects of varying the pulse conditions on device performance, including the irradiation fluence, pulse duration time, and number of pulses, were systematically investigated. Finally, it was successfully demonstrated that the IPWL treatment produces flexible polymer solar cells. The proposed IPWL process is suitable for the efficient industrial roll-to-roll production of polymer solar cells.