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Abstract A new sky-blue thermally activated delayed fluorescent (TADF) emitter TRZ-DCF, has been developed based on 2-(9H-carbazol-9-yl)-7,7-dimethyl-5,7-dihydroindeno[2,1- b ]carbazole (DCF) as donor and 2,4-diphenyl-1,3,5-triazine as acceptor. Due to the fusion of fluorene and carbazole moieties into the single carbazole donor, the multimodified emitter exhibits obvious TADF characteristics with a smaller singlet-triplet splitting (Δ E ST) value of 0.22 eV and relatively high photoluminance quantum yield (PLQY) of 84%. As a result, a maximum external quantum efficiency (EQE) of 18.7%, a current efficiency (CE) of 39.0 cd A−1 and a power efficiency (PE) of 30.5 lm W−1 with a Commission Internationale de L' Eclairage (CIE) coordinates of (0.18, 0.34), significantly surpassing the performance of the reference emitter 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-9H-carbazole (TRTZ), are achieved in optimal device construction. It is found that the EQE roll-off (20.8%) of TRZ-DCF is acceptable, that the efficiency drops to 14.8% at 1000 cd m−2 in optimal device construction. These results demonstrate the multiple modifications of weak electron-donating carbazole donor is an effective way of constructing high-efficiency blue TADF emitters with small roll-off. Graphical abstract Image 1 Highlights • We present a new sky-blue thermally activated delayed fluorescence emitter combining a novel multimodified carbazole donor moiety with triazine-based unit for efficient organic light-emitting diodes. • The external quantum efficiency (18.7%), singlet-triplet splitting (0.22 eV) and photoluminance quantum yield (84%) as well as the roll-off behavior (20.8%) of the emitter TRZ-DCF have been finely tuned through multiple modification of the reference emitter TRTZ. [ABSTRACT FROM AUTHOR]

Hole‐transporting materials (HTMs) play a significant role in hole transport and extraction for perovskite solar cells (PeSCs). As an important type of HTMs, the spiro‐architecture‐based material is widely used as small organic HTM in PeSCs with good photovoltaic performances. The skeletal modification of spiro‐based HTMs is a critical way of modifying energy level and hole mobility. Thus, many spiro alternatives are developed to optimize the spiro‐type HTMs. Herein, a novel carbazole‐based single‐spiro‐HTM named SCZF‐5 is designed and prepared for efficient PeSCs. In addition, another single‐spiro HTM SAF‐5 with reported 10‐phenyl‐10H‐spiro[acridine‐9,9′‐fluorene] (SAF) core is also synthesized for comparison. Through varying from SAF core to SCZF core as well as comparing with the classic 9,9′‐spiro‐bifluorene, it is found that the new HTM SCZF‐5 exhibits more impressive power conversion efficiency (PCE) of 20.10% than SAF‐5 (13.93%) and the commercial HTM spiro‐OMeTAD (19.11%). On the other hand, the SCZF‐5‐based device also has better durability in lifetime testing, indicating the newly designed SCZF by integrating carbazole into the spiro concept has good potential for developing effective HTMs. Two novel spiro‐type hole‐transporting materials (HTMs) SCZF‐5 and SAF‐5 are designed based on different spiro‐cores, SZCF and SAF, respectively, and are applied in the perovskite solar cells. An impressive power conversion efficiency of 20.10% is achieved in the SCZF‐5‐based device, which is obviously higher than that of commercial HTM spiro‐OMeTAD (19.11%) and SAF‐5 (13.93%). [ABSTRACT FROM AUTHOR]