Light-emitting　electrochemical　cells　(LECs)　as　simple　and　low-cost　electroluminescent　devices　are　one　of　the　most　promising　candidates　for　the　next-generation　flexible　and　large-area　solid-state　lighting　applications.　However,　the　development　of　efficient　emissive　materials　to　achieve　both　excellent　efficiency　and　stability,　especially　for　flexible　LECs,　remains　a　challenge.　Herein,　we　demonstrate　a　remarkable　enhancement　of　overall　device　performance　using　a　facile　and　feasible　di-nuclearization　strategy.　The　symmetrical　dinuclear　iridium(iii)　complex　(D-Ir2)　and　its　mononuclear　counterpart　(M-Ir1)　are　designed　and　synthesized.　Although　it　has　little　effect　on　the　emission　color,　the　adopted　approach　ingeniously　manipulates　the　intrinsic　photophysical　processes　and　solid-packing,　leading　to　distinct　LEC　performance.　Flexible　LECs　employing　D-Ir2　as　an　emitting　layer　realizes　a　current　efficiency　of　14.2　cd　A−1　and　external　quantum　efficiency　of　5.1%,　almost　twice　as　high　as　that　of　M-Ir1.　Encouragingly,　compared　with　a　short　half-lifetime　(t1/2)　of　190　min　for　M-Ir1,　the　D-Ir2-based　LEC　demonstrates　better　stability　in　the　open　air　with　t1/2　of　312　min.　The　large　decomposition　energy　of　ligands　and　facile　intersystem　crossing　supported　by　theoretical　calculations　account　for　its　superiority.　This　study　will　provide　a　new　perspective　for　constructing　phosphorescent　materials　suitable　for　high-performance　flexible　optoelectronics.　©　2023　The　Royal　Society　of　Chemistry.