The　highest　efficiencies　for　both　rigid　and　flexible　Cu2ZnSn(S,Se)4　(CZTSSe)　solar　cells　are　still　far　behind　the　theoretical　values.　This　is　mainly　due　to　band　tailing　in　absorber　and　a　large　recombination　near　absorber/Mo　interface　that　block　the　carrier　transportation　and　lead　to　Voc　and　FF　degradation,　which　are　mostly　noticeable　in　flexible　solar　cells.　In　this　paper,　CZTSSe　thin　films　were　prepared　on　flexible　Mo　substrates　by　green　solution-based　method　followed　by　selenization.　By　optimizing　selenization　conditions　(selenization　time　and　temperature),　dense　and　well　crystallized　CZTSSe　thin　films　without　micro-cracks　were　obtained　at　550　°C　for　12　min.　The　best　efficiency　of　6.78%　can　be　achieved　with　Voc　and　FF　enhanced　to　390.43　mV　and　57.71%.　The　dramatic　reductions　in　ideal　factor　A,　series　resistance　RS,　the　mismatch　Δ(Eg-PL)　and　potential　fluctuation　γ　indicate　that　band　tailing　and　recombination　are　significantly　reduced.　The　performance　degradation　with　bending　radius　and　cycles　is　studied　for　the　first　time　among　CZTSSe　solar　cells.　Results　indicate　long-term　stability　at　repeatable　release–stretch　cycles.　The　flexible　CZTSSe　solar　cells　with　high　stretch　ability　shed　light　on　the　development　of　flexible　solar　cells.　©　2018