<p>Achieving efficient polymeric organic light-emitting diodes (OLEDs) is desirable for applications in flexible and large-area display technologies but remains a challenge. In this work, through-space charge transfer (TSCT) and through-bond charge transfer (TBCT) are incorporated to accelerate the spin-flip processes of thermally activated delayed fluorescence (TADF) polymers. Furthermore, TBCT strength is optimized via changing the polymeric backbones, i.e, carbon-backbone or siloxane-backbone. Owing to the weak electron-withdrawing nature of silicon atoms, siloxane-backbone polymers present a higher extent of TBCT compared to carbon-backbone counterparts in addition to the comparable TSCT, thereby significantly improving the energy utilization efficiency. The excited state natures and photophysical properties of the polymers can effectively be optimized by changing the chemical structures of backbones. Finally, with the optimized copolymerization compositions, the prepared emitter PSiTCz₂mCP₈ (TCz is TADF units (<i>tert</i>-butylcarbazole and triazine); mCP is host units (1,3-bis(carbazol-9-yl) benzene)) achieves the higher radiative rate, reverse intersystem crossing rate, and photoluminescence quantum efficiency of ca. 95%. The solution-processed sky-blue OLEDs based on PSiTCz₂mCP₈ exhibit a maximum external quantum efficiency (EQE) of 26.6% and maintain an EQE of 21.4% at 500 cd m⁻² due to their high and balanced carrier transport characteristic, which achieves the highest maximum EQE (EQE_max) among all reported sky-blue TADF polymers. This study provides a new strategy for the design of high-performance polymeric electroluminescent materials.</p>