In solution, the quenching of triplet states by oxygen occurs through Dexter energy transfer, with the efficiency negatively correlated with the energy gap and positively correlated with the distance between donors and acceptors. Interestingly, the dendrimers under investigation exhibit significantly higher T1 levels of 2.86 and 2.89 eV compared with excited singlet oxygen ( 1 O2) of 0.97 eV, indicating an unfavorable quenching efficiency by oxygen. To gain further insights into the involvement of oxygen in the triplet quenching process, we measured the reactive oxygen species (ROS) generation for the three molecules under UV irradiation, employing 9,10anthracenediyl-bis(methylene)dimalonic acid (ABDA) as a singlet oxygen ( 1 O2) indicator (Fig. , Supplementary Fig. ). Under light irradiation, the absorbance peaks of ABDA exhibited gradual decreases in the presence of both dendrimers; however, BPSF displayed a rapid drop in ABDA absorption. The observed results suggest that the triplet excitons generated by the dendrimers exhibit lower production of 1 O2, indicating that the larger molecular volumes resulting from the dendronization of the shell package (with diameter of 20.1, 35.8, and 40.0 Å for BPSF, TCBPSF, and HCBPSF, respectively) effectively isolate the oxygen and inhibit triplet exciton quenching (Supplementary Fig. ). These findings serve as evidence that the implementation of air-stable intrinsic RTP has been successfully achieved in these dendrimers.