Development of a simple and effective patterning method applicable to solution-processable organic luminophores over a large area is critical for the cost-effective production of organic light-emitting-diode (OLED) displays. Here, we demonstrate highresolution patterning of light-emitting polymer active layers using a highly efficient photocrosslinker (4Bx). The photo-crosslinker is structured in a tetrabranched geometry, wherein a photo-crosslinkable azide moiety is present at each of the four corners of the molecule, and each of these moieties can form a chemical bond with light-emitting polymer semiconductors under UV irradiation. Due to the high crosslinking efficiency of 4Bx, the use of an unprecedentedly small amount of 4Bx (0.1 wt %) allows fully crosslinking lightemitting Super Yellow polymers without degrading their photoluminescence and electroluminescence characteristics. Furthermore, precisely defined photo-crosslinked patterns of Super Yellow with feature sizes of 5 μm are formed by using p-xylene as the developing solvent that was carefully selected according to a Hansen solubility parameter analysis.

White light is attained by combining different‐colored emissions. White organic light‐emitting diodes, therefore, should be fabricated to obtain mixed emissions from different organic luminophores while suppressing energy transfer between each other. Here, the authors present a simple means to realize this goal by forming two‐color strip‐patterns of light‐emitting polymer (orange) and an iridium complex (sky‐blue) luminophores entirely through solution processes. The formation of the two‐color patterns is facilitated by i) the use of a highly efficient crosslinker permitting the construction of structurally robust orange primary strip‐patterns and ii) the contrast in the surface energy allowing selective wetting of the secondary sky‐blue patterns between the orange primary patterns. The emissive layer comprising the two‐color strip ‐patterns allows for the mixing ratio of the two colors to be adjusted by simply varying the areal ratio of the two patterns, which in turn, controls the white emission color‐temperature from 2119 to 7994 K.