Two n-butoxy-encapsulated dendritic thermally activated delayed fluorescent (TADF) emitters (namely O-D1 and O-D2) with the first-/second-generation carbazoledendrons are designed and synthesized via C-N coupling between carbazoledendrons and 2,4,6-tris(4-bromophenyl)-1,3,5-triazine core.It is found that,compared with the commonly-used tert-butyl groups,the use of n-butoxy encapsulation groups can lead to smallersinglet-triplet energy gap for the dendrimers,producing stronger TADF effect together with faster reverse intersystem crossing process.Solution-processed TADF organic light-emitting diodes (OLEDs) utilizingalkoxy-encapsulated dendrimers O-D1 and O-D2 as emitters exhibitstate-of-the-art device efficiency withthe maximum external quantum efficiency up to 16.8％ and 20.6％,respectively,which are ～1.6 and ～2.0 times that of the tert-butyl-encapsulated counterparts.These results suggest that alkoxy encapsulation of the carbazole-based TADF dendrimers can be a promising approach for developing highly efficient emitters for solution-processed OLEDs.