Multivariate Analysis Identifying [Cu(N^N)(P^P)]+ Design and Device Architecture Enables First‐Class Blue and White Light‐Emitting Electrochemical Cells

White light‐emitting electrochemical cells (LECs) comprising only [Cu(N^N)(P^P)]+ have not been reported yet, as all the attempts toward blue‐emitting complexes failed. Multivariate analysis, based on prior‐art [Cu(N^N)(P^P)]+‐based thin‐film lighting (>90 papers) and refined with computational calculations, identifies the best blue‐emitting [Cu(N^N)(P^P)]+ design for LECs, that is, N^N: 2‐(4‐(tert‐butyl)phenyl)‐6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyridine and P^P: 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene, to achieve predicted thin‐film emission at 490 nm and device performance of 3.8 cd A−1@170 cd m−2. Validation comes from synthesis, X‐ray structure, thin‐film spectroscopic/microscopy/electrochemical characterization, and device optimization, realizing the first [Cu(N^N)(P^P)]+‐based blue‐LEC with 3.6 cd A−1@180 cd m−2. This represents a record performance compared to the state‐of‐the‐art tricoordinate Cu(I)‐complexes blue‐LECs (0.17 cd A−1@20 cd m−2). Versatility is confirmed with the synthesis of the analogous complex with 2‐(4‐(tert‐butyl)phenyl)‐6‐(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)pyrazine (N^N), showing a close prediction/experiment match: λ = 590/580 nm; efficiency = 0.55/0.60 cd A−1@30 cd m−2. Finally, experimental design is applied to fabricate the best white multicomponent host:guest LEC, reducing the number of trial‐error attempts toward the first white all‐[Cu(N^N)(P^P)]+‐LECs with 0.6 cd A−1@30 cd m−2. This corresponds to approximately ten‐fold enhancement compared to previous LECs (