Establishing reliable structure–processability relationships is essential for advancing organic solar cells (OSCs) toward scalable manufacturing. Herein, we present a comparative study of donor–acceptor (D–A) copolymers incorporating thiophene (T) and thienothiophene (TT) donor units, examining how donor and acceptor structure, polymerization outcome, molecular weight, operational solubility, and processing conditions are associated with film formation and device reproducibility under ambient blade-coating conditions. Six donor–acceptor copolymers (seven samples, including a TT3 batch prepared with a shorter reaction time, TT3*) were synthesized via Stille coupling and characterized with respect to molecular structure, molecular weight distribution, optoelectronic properties, thermal stability, thin-film morphology, and photovoltaic performance. TT-containing polymers showed distinct optical and processing behavior, but the present data do not isolate backbone conformation as the sole origin of these differences. Only the thiophene-based polymers T1, T2, and T3 could be processed into devices; among them, only T3 combined a high estimated degree of polymerization (DPn ≈ 25) with good film-forming ability, whereas T1 and T2 were obtained as short-chain materials (DPn ≈ 6). Among the investigated materials, T3 delivered the most reproducible device performance, reaching a power conversion efficiency of 2.69% in large-area (0.55 cm2) flexible OSCs. Rather than establishing a single causal relationship between backbone structure and device efficiency, this study highlights the combined importance of molecular structure, attainable molecular weight, solution processability, and processing tolerance for scalable ambient fabrication.
In this work, three thermally activated delayed fluorescence (TADF) materials with the same DMAC core, namely DMAC-TRZ, DMAC-MPM and DMAC-DPS, were employed as donors to construct exciplex organic light-emitting diodes (OLEDs) with acceptor 3P-T2T. The exciplex OLEDs based DMAC-TRZ: 3P-T2T achieved the best performance, delivering a maximum luminance of 34740 cd/m2, current efficiency of 36.8 cd/A, power efficiency of 33.6 lm/W and external quantum efficiency of 11.5%, respectively. Interestingly, all three devices showed similar efficiency levels, indicating that the DMAC donor unit in the TADF materials plays a major role in forming high efficiency exciplex, rather than the overall molecular structure of TADF donor. The high efficiency of DMAC-core donor: 3P-T2T exciplex systems is attributed to dual reverse intersystem crossing (RISC) process, the intrinsic RISC of the TADF donor together with the RISC of the exciplex, which significantly enhances triplet exciton utilization. Furthermore, warm white OLEDs were successfully fabricated by doping Rubrene/DCJTB emitters into the DMAC-TRZ: 3P-T2T exciplex host, respectively. This work demonstrated the effect of donor molecular structure on the performance of exciplex, which provided a feasible strategy for designing heavy-metal-free, low-cost and high efficiency exciplex OLEDs.
A series of novel uracil compounds interconnected by chalcone were synthesized and characterized. The chemical structures were confirmed using standard spectroscopic techniques, such as Fourier transform infrared spectroscopy, 1H and 13C NMR, and CHNO analysis. Phase behaviour was characterized and analyzed through POM and DSC analysis. Result indicated that the compounds were in mesophase. The smectic A phases contained focal-conic or Schlirene domains, in addition to the Schlieren texture nematic phase were observed. Mixing uracil compounds with hexagonal BN (h-BN) and copper oxide nanoparticles considerably enhanced the thermal conduction of the LCs. Adding 15 wt% copper oxide enhanced the LCs’ thermal conductivity from 0.42 W/m·K to 1.8 W/m·K. Mixing LCs with 35 wt% h-BN increased the thermal conductivity to 1.04 W/m·K. In addition, the thermal stability of the LCs was enhanced after doping with nanofillers, which occupied the free spaces between molecules and reduced the overall mobility of the compound. The electrical conductivity of the Schiff-base LCs was largely dependent on alkyl-chain length. The short chains (3a-3c) exhibited weak semiconducting behaviour, whereas the long chains (3g-3i) exhibited increased temperature sensitivity and disruption in charge transport order.
Halogenated solvents are widely used to fabricate high-performance organic solar cells (OSCs), but pose severe environmental and health risks. Developing efficient OSCs processed from non-halogenated solvents is therefore critical for industrial application. Herein, a simple benzodithiophene (BDT)-cored acceptor BDT-2H is utilized as the third component to fabricate ternary organic solar cells (OSCs) with a PM6:L8-BO host blend using the non-halogenated solvent toluene (TL). Benefiting from the favorable miscibility between BDT-2H and the PM6:L8-BO blend, the ternary active layer forms a well-defined bicontinuous interpenetrating network morphology. The optimized morphology endows the ternary OSCs with promoted exciton dissociation, balanced charge transport, and suppressed charge recombination relative to binary devices. Consequently, the optimized PM6:L8-BO:BDT-2H ternary device achieves a champion power conversion efficiency (PCE) of 18.09%, which is much higher than the 15.92% PCE of the binary PM6:L8-BO device. Furthermore, the universality of this ternary strategy is verified in the D18:BTP-eC9 system, yielding a higher PCE of 19.64%. This work demonstrates that simple BDT-based acceptors are promising guest components for ternary OSCs, offering a facile strategy to simultaneously optimize morphology and charge dynamics for environmentally friendly photovoltaics.
Robust electron injection materials are essential to efficient inverted organic light-emitting diodes (OLEDs). Herein, solution-processed Li2CO3:MnOx composite has been facilely synthesized and served as feasible electron injection layer for constructing efficient inverted ultraviolet (UV) OLEDs. Scanning electron microscope, atomic force microscope, and X-ray photoelectron spectroscopy characterization confirm that the Li2CO3:MnOx composite film exhibits smooth surface morphology and appropriate chemical states. Ultraviolet photoelectron spectroscopy measurements reveal that Li2CO3:MnOx composite reduces surface work function, and accordingly softening electron injection barrier. With Li2CO3:MnOx tailoring electron injection, the UV OLED shows maximum radiance of 18.26 mW/cm2 and external quantum efficiency of 2.36%, which are superior to the counterparts using pristine MnOx and Li2CO3. The current-voltage and impedance spectroscopy analysis of electron-only cells and finite-difference time-domain simulation collectively confirm that Li2CO3:MnOx composite is a robust electron injection material and thus benefiting to constructing efficient inverted UV OLEDs. Our work provides a facile solution-processed strategy for cathode interface controlling and advancing organic electronic devices.
