Journal Article Research Support, Non-U.S. Gov't deep-blue polymer light-emitting diodes deep‐blue flexible polymer light‐emitting diodes elastic‐plastic fully π‐conjugated polymer excellent energy dissipation capacity flexible polymer light‐emitting diodes internal plasticization strategy intrinsically stretchable π-conjugated polymers large‐area printed display semiconductor fluid plasticizing side‐chain internal plasticization single‐chain emission behavior strain tolerance capacity stretchable electroluminescent films stretchable fully π‐conjugated polymers film triphenylamine spirofunctionalization ultradeep‐blue polymer light‐emitting diodes ultra‐deep‐blue emission uniform deep‐blue emission wide bandgap light‐emitting diodes “Like Dissolves Like”