Talbot Dagenais

Bulk heterojunction (BHJ) morphologies are vital to the device performance of organic solar cells (OSCs), including phase separation in lateral and vertical directions. However, the morphology developed from the blend solution is not easily predicted and controlled, especially in the vertical direction, because the BHJ morphology is kinetically frozen during the rapid solvent evaporation process. Here, a simple approach to control BHJ morphologies with optimized phase distribution for small molecule:[6,6]-phenyl-C71-butyric acid methyl ester (PC₇₁ BM) blends by enhancing the substrate temperature during the spin-coating process. Three molecules with various fluorine atoms in the end acceptor units are selected. The relationship among molecular structures, substrate temperature effects on the morphology, and device performances are symmetrically investigated. Low temperature induces a multiple-sublayer-like architecture with significantly varied distributions of composition, morphology, and localized state energy, while high processing temperature induces more uniform film. The short-circuit current, open-circuit voltage, and fill factor of the devices are tuned with synergic improvement of efficiency toward over 10% and 11% for conventional and inverted devices. This work reveals the origination of vertical phase segregation, and provides a facile strategy to optimize the hierarchical phase separation for enhancing the performance of OSCs.

Vertical phase segregation in small molecule photovoltaic devices is manipulated via substrate temperature tuning. Low temperature induces multiple-sublayer-like architecture with significantly varied distributions of composition, morphology, and localized state energy, while high processing temperature induces more uniform film. The parameters of devices are largely tuned with synergic improvement of efficiency toward over 10% and 11% for conventional and inverted devices.

Herein are described the synthesis, photophysical properties and applications of a series of luminescent cyclometalated Au^III complexes having an auxiliary aryl ligand. These complexes show photoluminescence with emission quantum yields of up to 0.79 in solution and 0.84 in thin films (4 wt % in PMMA) at room temperature, both of which are the highest reported values among Au^III complexes. Thermally activated delayed fluorescence (TADF) is the emission origin for some of these complexes. Solution-processed OLEDs made with these complexes showed sky-blue to green electroluminescence with external quantum efficiencies (EQEs) of up to 23.8 %, current efficiencies of up to 70.4 cd A⁻¹, and roll-off of down to 1 %, highlighting the bright prospect of Au^III-TADF emitters in OLEDs.

Gold glows: Pincer Au^III aryl complexes give intense photoluminescence (PL) with emission quantum yields of up to 0.79 in solution and 0.84 in thin films. Some of them with N-substituents based on donor–acceptor structures display stronger PL from thermally activated delayed fluorescence (TADF). The OLEDs fabricated with these TADF emitters exhibit high external quantum efficiencies (EQEs) over 23 % (ISC=intersystem crossing).

WE NEED TO TALK ABOUT YOUR WEEKEND