NOVELTY - Naphthalene-based conjugated polymers (I) and (II) are new.    USE - New naphthalene-based conjugated polymer is used as electron donor material for film for forming device e.g. bulk heterojunction organic photovoltaic cell (all claimed).    DETAILED DESCRIPTION - Naphthalene-based conjugated polymers of formulae (I) and (II) are new.    G1,G2=ethenyl, ethynyl, 6-20C optionally substituted arylene, preferably unsubstituted arylene containing 1-3 heteroatoms chosen from O, S and N, or 4-12C optionally substituted heteroaryl, preferably unsubstituted heteroaryl containing heteroatom, preferably S;    A1,A2=group chosen from group of formulae (i)-(v);    D1,D2=group chosen from group of formulae (vi)-(viii);    X=C(O), C(S), C(O)O or C(S)O, preferably C(O);    Y',Z=1-30C alkyl, preferably 6-24C alkyl, more preferably 10-20C alkyl, 2-30C alkenyl, preferably 6-24C alkenyl, more preferably 10-20C alkenyl, 3-20C cycloalkyl, preferably 3-16C cycloalkyl, more preferably 3-12C cycloalkyl, 3-20C cycloalkenyl, preferably 3-16C cycloalkenyl, more preferably 3-12C cycloalkenyl, 4-30C cycloalkylalkyl, preferably 4-24C cycloalkylalkyl, more preferably 4-20C cycloalkylalkyl, 4-30 cycloalkenylalkyl, preferably 4-24C cycloalkenylalkyl, more preferably 4-20C cycloalkenylalkyl, 2-20C heterocyclyl, preferably 2-14C heterocyclyl, more preferably 3-10C heterocyclyl, 3-30C heterocyclylalkyl, preferably 3-22C heterocyclylalkyl, more preferably 3-18C heterocyclylalkyl, 6-20C aryl, preferably 6-16C aryl, more preferably 6-12C aryl, or 5-20C heteroaryl, preferably 5-16C heteroaryl, more preferably 5-12C heteroaryl;    q=1-3, preferably 1-2, more preferably 1;    m=5-100, preferably 8-60;and    n=5-100, preferably 8-60.    INDEPENDENT CLAIMS are included for the following:    (1) film, which comprises naphthalene-based conjugated polymers (I) or (II) as electron donor material, and has thickness of 1-1000 nm; and    (2) device, which comprises anode, cathode and photoactive layer comprising naphthalene-based conjugated polymers (I) or (II) and having thickness of 1-1000 nm.