NOVELTY - An electroluminescent copolymer, preferably a copolymer with a conjugated backbone, comprises: (a) at least one hole transport unit on one or more side-chain(s) of the copolymer; (b) at least one electron transport unit; (c) at least one unit A; and (d) optionally at least one emitter unit.    USE - The electroluminescent copolymer is useful for preparing formulation, preferably solution, dispersion or emulsion; and for manufacturing electronic device, e.g. PLED, OLED or OLEC (all claimed).    ADVANTAGE - The invention provides new materials for use in single layer PLEDs, which have advantageous properties, in particular good processability and long lifetime.    DETAILED DESCRIPTION - An electroluminescent copolymer, preferably a copolymer with a conjugated backbone, comprises: (a) at least one hole transport unit on one or more side-chain(s) of the copolymer; (b) at least one electron transport unit; (c) at least one unit A; and (d) optionally at least one emitter unit, where the highest occupied molecular orbitals (HOMOs) of both hole transport unit(s) and unit(s) A are at least 0.3 eV higher than the HOMO of the electron transport unit(s), preferably the HOMO of the hole transport unit(s) is higher than 0.3 eV and the HOMO of the unit(s) A is higher than 0.4 eV than the HOMO of the electron transport unit(s) and particularly preferably the HOMOs of both hole transport unit(s) and unit(s) A are at least 0.4 eV higher than the HOMO of the electron transport unit(s). INDEPENDENT CLAIMS are:    (1) formulation, preferably a solution, dispersion or emulsion, comprising the copolymer, and at least one solvent; and    (2) electronic device comprising the copolymer, preferably selected from organic light emitting diodes (OLED), polymer light emitting diodes (PLED), organic light emitting transistors (OLET), organic light emitting electrochemical cells (OLEC), organic light emitting electrochemical transistors (OLEETs), organic field effect transistors (OFET), thin film transistors (TFT), organic solar cells (O-SC), organic laser diodes (O-laser), organic integrated circuits (O-IC), radio frequency identification (RFID) tags, photodetector, sensors, logic circuits, memory elements, capacitor, charge injection layers, Schottky diodes, planarizing layers, antistatic films, conducting substrates or patterns, photoconductors, electrophotographic elements, organic solar concentrator, organic spintronic devices, and an organic plasmon emitting devices (OPEDs), particularly preferably the device is an PLED, OLED or OLEC.