TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Materials: At least one of the other partners B is of the same molecular group as A, preferably a molecular group, an atom or an ion. Group A is present as a single- or multi-charged cation or anion, which may be based on (a) pyridinium unit(s), preferably forming part of one or more polynuclear heterocycles, especially compounds of formula (a);R1-R4 = H, O, halogen (F, Cl, Br or I), hydroxyl, amino (e.g. diphenylamino or diethylamino), 1-20C aliphatic groups (e.g. methyl, ethyl or carboxyl), alkoxy (e.g. methoxy), cyano, sulfonic acid (or salts), 3-25C aryl (e.g. phenyl, pyridyl, naphthyl or part of a condensed ring);Groups of formula (b) pyrrolium, pyrylium, diazinium, thiazolium, thininium (sic), diazolium, thiadiazolium, tetrazolium or dithiolium units (preferably in polynuclear systems); orGroups of formula (c) boratabenzene units (preferably in polynuclear systems); or in the form ofgroups of formula (d) cationic or anionic dyes or other organic salts;Group of formula (e) various polycyclic aromatic structures and corresponding leuco bases, e.g. (A1) and (A2) (10 examples shown)X = CR4, SiR4, GeR4, SnR4, PbR4, N, P, R1, R2, R3 or R4;; orGroup of formula (f)Group of formulae (g);Group of formulae (h)n = a natural number;X, Z' (in f) = NR1, S or BR2;Xn = N or CR3R1, R2, R3, Rn = as for R1-R4 above;X, Z' (in g) = O, C(CN)2 or N-CN;Rn (in g) = known electron-withdrawing groups, or other groups as listed for R1-R4;X, X1, Z, Z1 (in h) = S or Se;R(in h) = as for Rn in g;Suitable chemically-stable compounds are C.I. Basic Yellow 37 or other diphenylmethane dyes, C.I. Basic Green 4 or other diamino derivatives of triphenylmethane dyes, C.I. basic Red 9 or other triamino derivatives of triphenylmethane dyes, Phenylene Blue or other indamine dyes, Pyronine B, C.I. Basic Red 11, Sacchareine (C.I. 45070), Rosamine, Rhodamine B or other diamino-xanthene dye derivatives, Coerulein B or other dihydroxy-xanthene dye derivatives, Acriflavine or other diamino-acridine derivatives, Phenosafranine or other azine dyes, C.I. Basic Blue 3 or other oxazine dyes, Lauth's Violet or other thiazine dyes, and N,N'-dialkylcyanines or N,N'-dialkyl-thiacarbocyanines or other methine or polymethine dyes (all with known counter-ions). These compounds contain (formal) positively-charged nitrogen, oxygen, phosphorus and/or sulfur, and/or negatively-charged boron, and may be in the form of a metal complex.One or more groups (A) may be linked with diazo groups (-N+equivalent toN) and may also contain -SO3- groups and/or ammonium, immonium, sulfonium, hydrazinium or thiouronium groups. The complex between (A) and (B) is such that (B) does not form a trap in the matrix (M) for the required majority charge-carrier. Material (I) is itself a mixture of materials. Preferred Method: Cleavage of (A) and (B) occurs only after insertion into material (II). This cleavage in the prepared layer and/or the removal of component (B) is an assisted process, preferably assisted by heating, optical excitation in the absorption range of the layer, exposure to molecular or atomic hydrogen or oxygen or to hydrogen or oxygen ions, addition of a third reactant which reacts with (B) to give a volatile product, reaction with a third reactant to form a product which is an anti-trap for the majority charge carrier or is easily removed from the layer, treatment in the gas phase, deflection of (B) with an electric or magnetic field, application of a strong electric field during the evaporation process, assistance in the solid phase in the evaporator (e.g. by heating in the solid, liquid or gas phase during vacuum deposition), adsorption of vapour on a reactive surface or a catalytic surface followed by desorption, irradiation with an intense laser beam, or plasma action during vapour deposition.The compound may be reacted with a third substance in the evaporator to give one or more products which are used as dopants; interaction with a catalyst may also occur in the evaporator source, and cleavage may be assisted by an electrochemical process on a suitable electrode. EXAMPLE - A mixed layer of naphthalenetetracarboxylic acid dianhydride (NTCDA) and Rhodamine B in a ratio of 150:1 (using Rhodamine B chloride as dopant) shows a conductivity of 1e-5 S/cm at room temperature, i.e. 4 times that of pure NTCDA. Field-effect measurements on NTCDA doped with Pyronine B (50:1) confirm the presence of electrons as majority charge carriers at a concentration of 1017/cm3; Seebeck measurements on this system also show n-conduction, with a Seebeck coefficient of -1.1 mV/K and therefore a higher charge carrier concentration than hitherto obtainable with doped NTCDA.