Optoelectronic devices and a method for producing the same

A method of producing an optoelectronic device comprising a light-emissive material provided between first and second electrical contacts comprising a polymer blend layer, the polymer blend layer comprising an optoelectronically active, first polymer, a charge transport second polymer, and a charge transport third polymer, the method comprising:

• providing a substrate comprising the first electrical contact,
• depositing the polymer blend on a first surface of the substrate in a fluid form,
• solidifying the polymer blend,
• forming the second contact over the solidified polymer blend layer,
• modifying surface energy of selected portions of the first surface of the substrate by plasma treatment to pattern the first surface of the substrate into areas having different surface energies, and
• depositing the polymer blend layer onto the patterned substrate surface under conditions which allow phase separation of the polymer blend under the influence of the different surface energies,
• wherein the phase separation is induced in the polymer blend layer in a controlled manner so as to control, in use, a propagation of light emitted by the light-emissive material in a predetermined direction and the phase separation is a lateral phase separation in the planar direction of the polymer blend layer,
• wherein the first surface of the substrate is selected to have more affinity towards the second polymer than the first polymer, but less affinity to the third polymer than the first polymer, and
• wherein the solidification of the polymer blend on the substrate is controlled such that the resulting polymer blend layer comprises a first portion adjacent to the first surface of the substrate having a relatively high proportion of the second polymer to facilitate, in use, a transport of charge between the first contact and the polymer blend layer, and a second portion opposite the first portion having a relatively high proportion of the third polymer to facilitate, in use, a transport of charge between the second contact and the polymer blend layer, the first and second portions being separated by a third portion having a relatively high proportion of the first polymer.