which have great potential to replace phosphorescent materials based on rare metal (like iridium or platinum) complexes in organic light-emitting diodes (OLEDs). [2] In this kind of so-called D-π-A structures, the intramolecular charge transfer can take place through covalent bond (TBCT). [3] By carefully modulating the twisted angle between donor and acceptor as well as their relative intensities, the singlet-triplet splitting energy (DE ST ) of the D-π-A compounds can be reduced. [4] Then, the reverse intersystem crossing (RISC) process can promote the triplet excitons up to the singlet low-lying state at due to such small DE ST after photo-or electroexcitation. Therefore, 100% internal quantum efficiency (IQE) can be theoretically achieved in OLEDs. Following this strategy, the D-π-A type TADF emitters covering R-G-B even the near infrared regions have been extensively studied. [5] Another way for small DE ST in TADF materials is to separate D/A moieties in unconjugated structures because the isolated D and A would result in a small overlap of highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for small electron exchange energy. [1d,6] Such D-σ-A type TADF emitters can be constructed by spiro junction, xanthene, triptycene, poly-styrene, etc., [7] and the relative intramolecular charge transfer process is through space (TSCT). [8] However, most of them exhibit mode rate photoluminescence quantum yield (PLQY) and relatively low electroluminescence especially in blue OLEDs. [9] Thus, the design paradigm of D-σ-A type TADF molecules still needs further investigations.In this work, we designed and synthesized a novel sky-blue spiro-type TADF emitter QAFCN, in which the donor and acceptor were not perpendicular to each other although they were connected through a spiro carbon. [5c,10] This was because the rigid donor moiety, 5,9-dihydroquinolino[3,2,1-de]acridine (QA), had a deformed conformation, which could bend the donor toward the acceptor moiety and thus shorten the D/A distance to facilitate the TSCT. [11] As compared to the classic spiro TADF emitter ACRFLCN, [9a] the QAFCN had blue-shifted emission, obviously higher PLQY and faster rate of RISC. Consequently, QAFCN-based device achieved an EQE of 17.9% Through-space charge transfer, which exists in nonconjugation linker based thermally activated delayed fluorescence (TADF) materials, excites chemists to explore more possibilities in organic light-emitting diodes (OLEDs). Herein, an sp 3 -hybrid carbon-centered donor-σ-acceptor type chromophore, QAFCN, is tentatively developed by exploring bi-acridine based electrondonor, i.e., 5,5-dimethyl-5,9-dihydroquinolino[3,2,1-de]acridine (QA). It is interesting to find that the QA moiety shows downshift in highest occupied molecular orbital because of its deformed geometry, which makes it qualified for sky-blue electroluminescence emission. Together with the blue-shift, enhanced photoluminescence quantum yield and faster reverse intersystem crossing rate are also o...