[6,6]-Phenyl-C61-butyric　acid-4＇-hydroxyl-azobenzene　ester　(PCBAb)　was　synthesized　and　used　as　the　acceptor　in　the　fabrication　of　reversible　UV-VIS　response　bi-state　polymer　solar　cells　(PSCs)　based　on　the　photoinduced　cis-trans　isomerization　of　PCBAb.　The　device　can　be　switched　between　＂active＇＇　and　＂sleep＇＇　by　the　irradiation　of　UV　and　visible　light,　respectively.　The　active　device　has　a　PCE　of　2.0%.　With　UV　irradiation,　the　device　goes　to　＂sleep＇＇　with　a　lowered　PCE　(0.4%),　and　simultaneously　decreased　J(sc),　V-oc　and　FF,　while　after　visible　light　treatment,　the　device　is　made　＂active＇＇　again.　The　mechanism　of　the　bi-state　process　involves　the　different　electron　mobilities　of　the　isomers.　(C)　2015　Elsevier　B.V.　All　rights　reserved.