TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Matrix: Matrix (a) forms a glass-like layer, has a Tg above 70degreesC and is of formula (1)-(9) or of formula (11) -(15) or (10)X = O, S or SeThe matrix contains a polymer or dendrimer, the polymer optionally being conjugated and especially being a polyfluorene, polyspirobifluorene, poly-p-phenylene, polycarbazole, polyvinyl carbazole or polythiophene or a copolymer of these.Preferred Emitter: Emitter (b) has an element of atomic weight 38-84 (especially 56 - 80), this element being molybdenum, tungsten, rhenium, ruthenium, osmium, rhodium, iridium, palladium, platinum, silver, gold or europium and (b) being especially of formula (16) - (19)DCy = a cyclic group containing a donor atom which bonds it to a metal atom, the group being covalently bonded to CCy and optionally substituted by R9;CCy = a cyclic group containing a carbon atom which bonds it to a metal, the group being optionally substituted by R9;R9 = (a) H, F, Cl, Br, I, NO2, CN or an optionally cyclic 1-40C alkyl or alkoxy group with one or more non-adjacent -CH2- groups replaced by -R4C=CR4-, -Ctriple bondC-, C=O, C=S, C=Se, C=NR4, -O-, -S-, - NR5- or -CONR6- and optionally with one or more H replaced by F or (b) a 4-40C (hetero)aromatic optionally substituted by R9 where the R9's are on the same or different rings or stretch between a mono and poly-cyclic aliphatic or aromatic ring system; andL = a bidentate chelating ligand.Preferred Composition: The (a) + (b) mixture contains the emitter (b) at 1-99 wt.%    TECHNOLOGY FOCUS - POLYMERS - Preferred Matrix : The matrix contains a polymer or dendrimer, the polymer optionally being conjugated and especially being a polyfluorene, polyspirobifluorene, poly-p-phenylene, polycarbazole, polyvinyl carbazole or polythiophene or a copolymer of these. EXAMPLE - An electronic device with maximum efficiency = 30 cd/A, voltage at 100 cd/m2 = 4.6v and life-span at 10 mA/cm2 = 400 hours comprised a 20 nm emitter layer containing bis(9,9'-spirobifluoren-2-yl)ketone + 20% iridium tris-phenylpyridine (Ir(PPh)3), a 10 mn hole-blocking layer of 2,9-dimethyl-4,7- diphenyl-1,10-phenanthroline (BCP) and a 10 nm electron transport layer of tris(quinolinolato) aluminum. The corresponding values for a control with BCP replacing the bis(9,9'- spirobifluoren-2-yl)ketone) as matrix in the emitter layer were 25 cd/a, 4.8 v and only 150 hours respectively.