The　identifying　characteristic　of　an　organic　electrochemical　transistor　(OECT)　is　the　coupling　between　ionic　and　electronic　charges　within　the　entire　volume　of　the　channel.　In　this　work,　by　taking　advantage　of　the　volumetric　nature　of　the　OECTs＇　response,　a　novel　flexible　photodetector　is　reported　for　the　first　time　based　on　all-solid-state　OECT　with　an　excellent　responsivity　of　up　to　6.7　×　106　A/W,　detectivity　as　high　as　3.6　×　1013　Jones,　and　a　fast　response　of　0.13　s　in　the　visible　range,　which　are　superior　to　those　of　the　majority　of　the　reported　organic　phototransistors　(OPTs)　based　on　field-effect　transistors　(FETs)　and　even　better　than　those　of　FET-based　phototransistors　with　two-dimensional　(MoS2　and　graphene)　and　perovskite　materials.　The　high　performance　of　the　devices　was　ascribed　to　the　combination　of　the　higher　carrier　mobility　of　poly(3,4-ethylenedioxythiophene)　doped　with　poly(styrene　sulfonate)　(PEDOT:PSS)　as　a　channel　and　the　volumetric　nature　of　the　OECTs＇　response,　and　the　charge　density　of　the　volumetric　channel　was　efficiently　modulated　by　incident　light　compared　to　FETs.　Moreover,　OECT-based　OPTs　with　quantum　dots　(CdSe/ZnS)　as　a　light　sensitizer　were　characterized　under　ultraviolet　light,　and　they　exhibited　excellent　photosensitivity,　which　further　verified　the　superiority　of　OECT　for　phototransistors.　Furthermore,　a　flexible　image　sensor　was　fabricated　for　the　first　time　by　integrating　flexible　OECTs-OPTs　into　a　10　×　10　array,　which　can　clearly　identify　the　target　image　under　a　bending　state,　indicating　the　great　potential　of　OECTs-OPTs　in　the　application　of　low-power,　ultrasensitive　flexible　photodetectors　and　imaging　technology.　©　2019　American　Chemical　Society.