A new class of bis-tridentate Ir(III) complexes (Dap-1−4) was synthesized using carbene pincer pro-chelates PC1•H 3 (PF 6 ) 2 or PC2•H 3 (PF 6 ) 2 with either imidazolylidene or imidazo [4,5-b]pyridin-2-ylidene appendages, together with a second cyclometalating 2,6-diaryoxypyridine chelate, L1H 2 and L2H 2 , differed by a NMe 2 donor at the central pyridinyl fragment. The respective emission tuning between the ultraviolet and blue region was rationalized using time-dependent density functional theory (TD-DFT) approaches. Next, a highly efficient blue emitter (Dap-5) was synthesized by concomitant addition of two methyl groups and a single CF 3 substituent at the central phenyl and peripheral imidazo[4,5-b]pyridin-2-ylidene entities of the carbene pincer chelate, respectively. The organic light-emitting diode (OLED) device with 15 wt % Dap-5 in DPEPO shows electroluminescence at 468 nm and with CIE (0.14, 0.15) and a max external quantum efficiency (max EQE) of 16.8% with low efficiency roll-off (EQE of 14.4% at 1000 cd m −2 ); the latter is attributed to the relatively shortened triplet excitedstate radiative lifetime. These results highlight the adequateness of bis-tridentate Ir(III) phosphors in fabrication of practical blue-emitting OLEDs.

Two-dimensional (2D) Dion−Jacobson (DJ) perovskite solar cells (PSCs), despite their advantage in versatility of n-layer variation, are subject to poor photovoltaic efficiency, particularly in the fill factor (FF), compared to their three-dimensional counterparts. To enhance the performance of DJ PSCs, the process of growing crystals and hence the corresponding morphology of DJ perovskites are of prime importance. Herein, we report the fast nonisothermal (NIT) crystallization protocol that is previously unrecognized for 2D perovskites to significantly improve the morphology, orientation, and charge transport of the DJ perovskite films. Comprehensive mechanistic studies reveal that the NIT effect leads to the secondary crystallization stage, forming network-like channels that play a vital role in the FF's leap-forward improvement and hence the DJ PSC's performance. As a whole, the NIT crystallized PSCs demonstrate a high power conversion efficiency and an FF of up to 19.87 and 86.16%, respectively. This research thus provides new perspectives to achieve highly efficient DJ PSCs.

Four isomeric, homoleptic iridium(III) metal complexes bearing 5-(trifluoromethyl)imidazo[4,5-b]pyridin-2-ylidene and 6-(trifluoromethyl)imidazo[4,5-b]pyridin-2-ylidene-based cyclometalating chelates are successfully synthesized. The meridional isomers can be converted to facial isomers through acid induced isomerization. The m-isomers display a relatively broadened and red-shifted emission, while f-isomers exhibit narrowed blue emission band, together with higher photoluminescent quantum yields and reduced radiative lifetime relative to the mer-counterparts. Maximum external quantum efficiencies of 13.5% and 22.8% are achieved for the electrophosphorescent devices based on f-tpb1 and m-tpb1 as dopant emitter together with CIE coordinates of (0.15, 0.23) and (0.22, 0.45), respectively. By using f-tpb1 as the sensitizing phosphor and t-DABNA as thermally activated delayed fluorescence (TADF) terminal emitter, hyperluminescent OLEDs are successfully fabricated, giving high efficiency of 29.6%, full width at half maximum (FWHM) of 30 nm, and CIE coordinates of (0.13, 0.11), confirming the efficient Förster resonance energy transfer (FRET) process.

We propose a new concept exploiting thermally activated delayed fluorescence (TADF) molecules as photosensitizers, storage units and signal transducers to harness solar thermal energy. Molecular composites based on the TADF core phenoxazine–triphenyltriazine (PXZ-TRZ) anchored with norbornadiene (NBD) were synthesized, yielding compounds PZDN and PZTN with two and four NBD units, respectively. Upon visible-light excitation, energy transfer to the triplet state of NBD occurred, followed by NBD → quadricyclane (QC) conversion, which can be monitored by changes in steady-state or time-resolved spectra. The small S1-T1 energy gap was found to be advantageous in optimizing the solar excitation wavelength. Upon tuning the molecule’s triplet state energy lower than that of NBD (61 kcal/mol), as achieved by another composite PZQN, the efficiency of the NBD → QC conversion decreased drastically. Upon catalysis, the reverse QC → NBD reaction occurred at room temperature, converting the stored chemical energy back to heat with excellent reversibility.

Inverted perovskite solar cells (PSCs) have attracted intense attention because of their insignificant hysteresis and low-temperature fabrication process. However, the efficiencies of inverted PSCs are still inferior to those of commercialized silicon solar cells. Also, the poor stability of PSCs is one of the major impedances to commercialization. Herein, we rationally designed and synthesized a new series of electron donor ( R , R -diphenylamino) and acceptor (pyridimium-(CH 2 ) n -sulfonates) zwitterions as a boundary modulator and systematically investigated their associated interface properties. Comprehensive physical and optoelectronic studies verify that these zwitterions provide a four-in-one functionality: balancing charge carrier transport, suppressing less-coordinated Pb 2+ defects, enhancing moisture resistance, and reducing ion migration. Although each functionality may have been reported by specific passivating molecules, a strategy that simultaneously regulates the charge-transfer balance and three other functionalities has not yet been developed. The results are to make an omnidirectional improvement of PSCs. Among all zwitterions, 4-(4-(4-(di-(4-methoxylphenyl)amino)phenyl)propane-1-ium-1-yl)butane-1-sulfonate (OMeZC3) optimizes the balance hole/electron mobility ratio of perovskite to 0.91, and the corresponding PSCs demonstrate a high power conversion efficiency (PCE) of up to 23.15% free from hysteresis, standing out as one of the champion PSCs with an inverted structure. Importantly, the OMeZC3-modified PSC exhibits excellent long-term stability, maintaining almost its initial PCE after being stored at 80% relative humidity for 35 days.