Organic solar cell

An organic solar cell comprising:

• a first electrode;
• a second electrode on the first electrode;
• and
• one or more organic material layers between the first electrode and the second electrode and including a photoactive layer,
• wherein the photoactive layer comprises an electron donor and an electron acceptor,
• the electron donor comprises a polymer comprising a first unit of Chemical Formula 1, a second unit of Chemical Formula 2, and a third unit of Chemical Formula 3:
• wherein:
• X1 to X5 are the same as or different from each other, and each is independently selected from the group consisting of CRR′, NR, O, SiRR′, PR, S, GeRR′, Se and Te;
• Y1 to Y4 are the same as or different from each other, and each is independently selected from the group consisting of CR″, N, SiR″, P and GeR″;
• R, R′, R″, Q1 to Q4, R1 to R4, R10 and R11 are the same as or different from each other, and each is independently hydrogen, deuterium, a halogen group, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted amine group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group;
• R20 and R21 are the same as or different from each other, and each is independently a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted aryloxy group;
• a, b, d and e are each an integer of 0 to 3;
• when a, b, d or e is 2 or greater, structures in the two or more parentheses are the same as or different from each other;
• and
• A1 to A4 are the same as or different from each other, and each is independently hydrogen, fluorine or chlorine, and at least one of A1 to A4 is fluorine or chlorine,
• wherein the polymer comprises a unit of Chemical Formula 5:
• wherein:
• R27 to R30 are the same as or different from each other, and each is independently a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group;
• R31 to R42 are the same as or different from each other, and each is independently hydrogen, or a substituted or unsubstituted alkyl group;
• A1 and A4 have the same definitions as in Chemical Formula 1;
• l is, as a mole fraction, a real number of 0<l<1;
• m is, as a mole fraction, a real number of 0<m<1;
• l+m=1;
• and
• n is, as a unit repetition number, an integer of 1 to 10,000, and
• wherein the electron acceptor includes a non-fullerene-based compound of Chemical Formula A-1: