Amplified spontaneous emission from internal energy transfer process in the copolymer BEHP-co-MEH-PPV

► ASE was produced in the copolymer BEHP-co-MEH-PPV in a few organic solutions. ► ASE exist at 560 nm in BEHP-co-MEH-PPV, which is non- excimeric state of MEH-PPV. ► In case of MEH-PPV polymer alone ASE exist in the excimeric state. ► BEHP-PPV segment force the whole molecule to produce ASE in MEH-PPV singlet state. ► MEH-PPV has better ASE properties overall compared with BEHP-co-MEH-PPV or Rh 6G.