In a method of forming an organic light emitting structure, a plurality of first electrodes spaced apart from each other is formed on a lower substrate. A first organic layer covering the first electrodes is formed on the lower substrate. A preliminary pixel defining layer is formed on the first organic layer. The preliminary pixel defining layer includes a photosensitive material, and is selectively exposed to light so that the preliminary pixel defining layer and a portion of the first organic layer beneath the preliminary pixel defining layer are transformed into a pixel defining layer and a first organic layer pattern, respectively. An emitting layer is formed on the first organic layer exposed by the pixel defining layer. A second organic layer is formed on the emitting layer. A second electrode is formed on the second organic layer.