An organic semiconducting layer formulation, which comprises: an organic binder which has a permittivity, ∈, at 1,000 Hz of 3.3 or less; and a polyacene compound of Formula: A: wherein: each of R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11 and (R12, which may be the same or different, independently represents hydrogen; an optionally substituted C1-C40 carbyl or hydrocarbyl group; an optionally substituted C1-C40 alkoxy group; an optionally substituted C6-C40 aryloxy group; an optionally substituted C7-C40 alkylaryloxy group; an optionally substituted C2-C40 alkoxycarbonyl group; an optionally substituted C7-C40 aryloxycarbonyl group; a cyano group (—CN); a carbamoyl group (—C(═O)NH2); a haloformyl group (—C(═O)—X, wherein X represents a halogen atom); a formyl group (—C(═O)—H); an isocyano group; an isocyanate group; a thiocyanate group or a thioisocyanate group; an optionally substituted amino group; a hydroxy group; a nitro group; a CF3 group; a halo group (CI, Br, F); or an optionally substituted silyl group; and wherein independently each pair of R2 and R3 and/or R8 and R9, may be cross-bridged to form a C4-C40 saturated or unsaturated ring, which saturated or unsaturated ring may be intervened by an oxygen atom, a sulphur atom or a group shown by formula —N(Ra)— (wherein Ra is a hydrogen atom or an optionally substituted hydrocarbon group), or may optionally be substituted; and wherein one or more of the carbon atoms of the polyacene skeleton may optionally be substituted by a heteroatom selected from O N, P, As, O, S, Se and Te; and wherein independently any two or more of the substituents R1-R12 which are located on adjacent ring positions of the polyacene may, together, optionally constitute a further C4-C40 saturated or unsaturated ring optionally interrupted by O, S or —N(Ra) where Ra is as defined above) or an aromatic ring system, fused to the polyacene; and wherein n is 0, 1, 2, 3 or 4, also claimed is an electronic device, particularly an organic field effect transistor comprising the organic semiconductor layer formulation.