Where smaller ΔEST, coupled with an increased number of ISC channels and larger spin-orbit coupling operator ( 𝐻 ̂𝑆𝑂𝐶 ) can enhance the ISC rate. Firstly, the dendronization strategy was found to preserve a small overlap between HOMOs and LUMOs, located on the donor and acceptor moieties, respectively (Supplementary Fig. ), resulting in a very small ΔEST (0.02 and 0.14 eV), which is favorable for the ISC process. Secondly, the introduction of dendrons reduces the triplet-triplet energy gaps (ΔETT) and increases the density of triplet states, which promotes ISC channels from S1 to Tn. Specifically, the dendronization of BPSF leads to the introduction of valid ISC channels with both small ΔEST (≤ 0.37 eV) and high SOC values (≥ 0.3 cm -1 ). As a result, the number of valid ISC routes increases from two to four, enabling the isolated dendrimer to exhibit intrinsic RTP. Thirdly, within the central-field approximation, when the spin of an electron is flipped over, 𝐻 ̂𝑆𝑂𝐶 either suppresses or reinforces πconjugation, leading to differing extents of π-conjugation. Consequently, the SOC matrix element values for ISC can be qualitatively estimated by evaluating the changes in π-conjugation within the hole or electron wave functions between the singlet and triplet excited states. In Fig. , In addition to achieving efficient ISC, another crucial factor for enhancing phosphorescence is increasing the kP. The kP is primarily determined by the transition dipole moment between the T1 and S0 states (𝜇 𝑇 1 →𝑆 0 ), which can be expressed as equation (2,3). 25