The　development　of　high-quality　organic　scintillators　encounters　challenges　primarily　associated　with　the　weak　X-ray　absorption　ability　resulting　from　the　presence　of　low　atomic　number　elements.　An　effective　strategy　involves　the　incorporation　of　halogen-containing　molecules　into　the　system　through　co-crystal　engineering.　Herein,　we　synthesized　a　highly　fluorescent　dye,　2,5-di(4-pyridyl)thiazolo[5,4-d]thiazole　(Py2TTz),　with　a　fluorescence　quantum　yield　of　12.09%.　Subsequently,　Py2TTz　was　co-crystallized　with　1,4-diiodotetrafluorobenzene　(I2F4B)　and　1,3,5-trifluoro-2,4,6-triiodobenzene　(I3F3B)　obtaining　Py2TTz-I2F4　and　Py2TTz-I3F3.　Among　them,　Py2TTz-I2F4　exhibited　exceptional　scintillation　properties,　including　an　ultrafast　decay　time　(1.426　ns),　a　significant　radiation　luminescence　intensity　(146%　higher　than　Bi3Ge4O12),　and　a　low　detection　limit　(70.49　nGy　s−1),　equivalent　to　1/78th　of　the　detection　limit　for　medical　applications　(5.5　μGy　s−1).　This　outstanding　scintillation　performance　can　be　attributed　to　the　formation　of　halogen-bonding　between　I2F4B　and　Py2TTz.　Theoretical　calculations　and　single-crystal　structures　demonstrate　the　formation　of　halogen-bond-induced　rather　than　π-π-induced　charge-transfer　cocrystals,　which　not　only　enhances　the　X-ray　absorption　ability　and　material　conductivity　under　X-ray　exposure,　but　also　constrains　molecular　vibration　and　rotation,　and　thereby　reducing　non-radiative　transition　rate　and　sharply　increasing　its　fluorescence　quantum　yields.　Based　on　this,　the　flexible　X-ray　film　prepared　based　on　Py2TTz-I2F4　achieved　an　ultrahigh　spatial　resolution　of　26.8　lp　per　mm,　underscoring　the　superiority　of　this　strategy　in　developing　high-performance　organic　scintillators.　©　2024　The　Royal　Society　of　Chemistry.