This thesis deals with the synthesis and characterization of photosensitive polyaniline derivatives. Starting from the intrinsic conductive polymers polyaniline and poly-o-toluidine the corresponding non-conductive N-formyl derivatives were obtained by a formylation reaction. An illumination with UV light of thin films of such polymers leads to the decomposition of the N-formyl group resulting in the formation of the initial conductive polymers. This photodecarbonylation reaction was studied using FTIR and UV/VIS spectroscopy. Moreover, thin films of these polymers were patterned via photolithographic methods. Patterned conductive polymer films were obtained by a subsequent doping of the irradiated areas with hydrochloric acid. In addition the irradiated areas became insoluble in organic solvents after protonation. Due to this fact a negative-tone image could be achieved upon the development with dimethylformamide. The difference in conductivity of these patterned polymer layers were investigated by means of conductive atomic force microscopy (CAFM). Moreover, it turned out that the sheet conductivity of poly-N-formylaniline layers depends on the conversion of the photoreaction. In a further step thin films of poly-N-formylaniline were applied as photopatternable hole-transport layer in organic light emitting diodes.