A TADF compound according to formula III: wherein each Het is an aromatic heterocyclic acceptor moiety and each D is a donor moiety, wherein R* is, independently for each occurrence, selected from the group consisting of -H, alkyl, aryl or heteroaryl, the aromatic heterocyclic acceptor moieties Het are, independently for each occurrence selected from the group consisting of: wherein -L represents the bonding position to ring III, X represents O, S or NR 2 and groups R 2 are, independently for each occurrence, selected from the group consisting of -H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated; substituted or unsubstituted aryl or heteroaryl; wherein groups R 1 are, independently for each occurrence, selected from the group consisting of -H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated; substituted or unsubstituted aryl or heteroaryl, -CF 3, -OMe, -SF 5, -NO 2, halo, aryl, aryl hydroxy, amino, alkoxy, alkylthio, carboxy, cyano, thio, formyl, ester, acyl, thioacyl, amido, sulfonamido, carbamate, phosphine oxide and phosphine sulphide, and wherein donor moieties D are independently for each occurrence selected from: wherein -L represents the bonding position to ring III that is para to the nitrogen in structures C, D, G and H; X 1 is selected from the group consisting of O, S, NR, SiR 2, PR and CR 2, wherein each R is independently selected from the group consisting of -H, alkyl, aryl or heteroaryl; each Ar is independently for each occurrence selected from the group consisting of substituted or unsubstituted aryl or heteroaryl; and represents, independently for each occurrence a substituted or unsubstituted aryl or heteroaryl ring fused to the central ring of structures A, B,C, D, E or F, for example a five or a six membered substituted or unsubstituted aryl or heteroaryl ring; and n () indicates the optional presence of saturated -CH 2 - groups in the rings annelated to the benzene ring, wherein n is independently for each occurrence, 0, 1, or 2. wherein each Het is an aromatic heterocyclic acceptor moiety and each D is a donor moiety, wherein R* is, independently for each occurrence, selected from the group consisting of -H, alkyl, aryl or heteroaryl, the aromatic heterocyclic acceptor moieties Het are, independently for each occurrence selected from the group consisting of: wherein -L represents the bonding position to ring III, X represents O, S or NR 2 and groups R 2 are, independently for each occurrence, selected from the group consisting of -H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated; substituted or unsubstituted aryl or heteroaryl; wherein groups R 1 are, independently for each occurrence, selected from the group consisting of -H, substituted or unsubstituted primary, secondary or tertiary alkyl, that may be cyclic and may be unsaturated; substituted or unsubstituted aryl or heteroaryl, -CF 3, -OMe, -SF 5, -NO 2, halo, aryl, aryl hydroxy, amino, alkoxy, alkylthio, carboxy, cyano, thio, formyl, ester, acyl, thioacyl, amido, sulfonamido, carbamate, phosphine oxide and phosphine sulphide, and wherein donor moieties D are independently for each occurrence selected from: wherein -L represents the bonding position to ring III that is para to the nitrogen in structures C, D, G and H; X 1 is selected from the group consisting of O, S, NR, SiR 2, PR and CR 2, wherein each R is independently selected from the group consisting of -H, alkyl, aryl or heteroaryl; each Ar is independently for each occurrence selected from the group consisting of substituted or unsubstituted aryl or heteroaryl; and represents, independently for each occurrence a substituted or unsubstituted aryl or heteroaryl ring fused to the central ring of structures A, B,C, D, E or F, for example a five or a six membered substituted or unsubstituted aryl or heteroaryl ring; and n () indicates the optional presence of saturated -CH 2 - groups in the rings annelated to the benzene ring, wherein n is independently for each occurrence, 0, 1, or 2.