An organic semiconductor formulation comprising: a hydrocarbon solvent; an aromatic additive, is from 0.01wt% to 10 wt% of the hydrocarbon solvent; a fullerene or small molecular acceptor; and a conjugated polymer donor, comprises one or more repeating units of the following formula: wherein each Y is independently selected from the group consisting of N, C-H, and C-R1, wherein R1 is selected from the group consisting of C1-30 straight-chain and branched alkyl groups; each X 1 is independently selected from the group consisting of S and Se; each R is independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 21-40 C atoms, wherein one or more non-adjacent C atoms are optionally replaced by -O-, -S-, -C -, -C(O-)-O-, -O-C -, - O-C -O-, -CR 0 =CR 00 -, or -C=C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryloxy, heteroaryloxy, arylcarbonyl, heteroarylcarbonyl, arylcarbonyloxy, heteroarylcarbonyloxy, aryloxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms, wherein R0 and R00 are independently a straight-chain, branched, or cyclic alkyl group; Ar 1 is selected from the group consisting of: wherein each X 2 is independently selected from the group consisting of S, Se, O, and N-R2, wherein R2 is selected from C1-30 straight-chain or branched alkyl groups; and each X 3 is independently selected from the group consisting of F, Cl, H, and Br; and Ar 2 is selected from the group consisting of monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar2 may contain one to five of said arylene or heteroarylene each of which may be fused or linked; and wherein the conjugated polymer is not poly(3-hexylthiophene-2,5-diyl) (P3HT). a hydrocarbon solvent; an aromatic additive, is from 0.01wt% to 10 wt% of the hydrocarbon solvent; a fullerene or small molecular acceptor; and a conjugated polymer donor, comprises one or more repeating units of the following formula: wherein each Y is independently selected from the group consisting of N, C-H, and C-R1, wherein R1 is selected from the group consisting of C1-30 straight-chain and branched alkyl groups; each X 1 is independently selected from the group consisting of S and Se; each R is independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 21-40 C atoms, wherein one or more non-adjacent C atoms are optionally replaced by -O-, -S-, -C -, -C(O-)-O-, -O-C -, - O-C -O-, -CR 0 =CR 00 -, or -C=C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryloxy, heteroaryloxy, arylcarbonyl, heteroarylcarbonyl, arylcarbonyloxy, heteroarylcarbonyloxy, aryloxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms, wherein R0 and R00 are independently a straight-chain, branched, or cyclic alkyl group; Ar 1 is selected from the group consisting of: wherein each X 2 is independently selected from the group consisting of S, Se, O, and N-R2, wherein R2 is selected from C1-30 straight-chain or branched alkyl groups; and each X 3 is independently selected from the group consisting of F, Cl, H, and Br; and Ar 2 is selected from the group consisting of monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar2 may contain one to five of said arylene or heteroarylene each of which may be fused or linked; and wherein the conjugated polymer is not poly(3-hexylthiophene-2,5-diyl) (P3HT). each Y is independently selected from the group consisting of N, C-H, and C-R1, wherein R1 is selected from the group consisting of C1-30 straight-chain and branched alkyl groups; each X 1 is independently selected from the group consisting of S and Se; each R is independently selected from the group consisting of straight-chain, branched, and cyclic alkyl with 21-40 C atoms, wherein one or more non-adjacent C atoms are optionally replaced by -O-, -S-, -C -, -C(O-)-O-, -O-C -, - O-C -O-, -CR 0 =CR 00 -, or -C=C-, and wherein one or more H atoms are optionally replaced by F, Cl, Br, I, or CN or denote aryl, heteroaryl, aryloxy, heteroaryloxy, arylcarbonyl, heteroarylcarbonyl, arylcarbonyloxy, heteroarylcarbonyloxy, aryloxycarbonyl, or heteroaryloxycarbonyl having 4 to 30 ring atoms, wherein R0 and R00 are independently a straight-chain, branched, or cyclic alkyl group; Ar 1 is selected from the group consisting of: wherein each X 2 is independently selected from the group consisting of S, Se, O, and N-R2, wherein R2 is selected from C1-30 straight-chain or branched alkyl groups; and each X 3 is independently selected from the group consisting of F, Cl, H, and Br; and Ar 2 is selected from the group consisting of monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar2 may contain one to five of said arylene or heteroarylene each of which may be fused or linked; and each X 2 is independently selected from the group consisting of S, Se, O, and N-R2, wherein R2 is selected from C1-30 straight-chain or branched alkyl groups; and each X 3 is independently selected from the group consisting of F, Cl, H, and Br; and Ar 2 is selected from the group consisting of monocyclic, bicyclic, and polycyclic arylene, and monocyclic, bicyclic, and polycyclic heteroarylene, wherein Ar2 may contain one to five of said arylene or heteroarylene each of which may be fused or linked; and wherein the conjugated polymer is not poly(3-hexylthiophene-2,5-diyl) (P3HT).