A polymer solar cell includes an anode electrode, a photoactive layer, and a cathode electrode stacked on each other in that order. The photoactive layer includes a polymer layer and a plurality of carbon nanotubes dispersed in the polymer layer. Each of the plurality of carbon nanotubes includes a first carbon nanotube portion and a second carbon nanotube portion. The first carbon nanotube portion is embedded in the polymer layer, and the second carbon nanotube portion is exposed out of the polymer layer and directly contacts the cathode electrode.