Facile Strategy for Third Component Optimization in Wide-Band-Gap π-Conjugated Polymer Donor-Based Efficient Ternary All-Polymer Solar Cells.

Emerging organic solar cells based on a ternary strategy is one of the most effective methods for improving the blend film morphology, absorption ability, and device performances. On the other hand, this strategy has had very limited success in all-polymer solar cells (all-PSCs) because of the scarcity of new polymers and the challenges faced during third component optimization. Herein, highly efficient ternary all-PSCs were developed from siloxane-functionalized side chains with a wide-band-gap (Eg) polymer, Si-BDT, which is blended with a medium and ultra-narrow Eg polymer donor and acceptor, PTB7-Th, and DCNBT-TPIC. An impressive power conversion efficiency (PCE) of 13.45% was achieved in the ternary all-PSCs [PTB7-Th(0.6):Si-BDT(0.4):DCNBT-TPIC(0.6)] with the addition of 0.4 wt equivalent Si-BDT into binary all-PSCs [PTB7-Th(1):DCNBT-TPIC(0.6) PCE of 10.11%]. In contrast, the binary all-PSCs with a Si-BDT(1):DCNBT-TPIC(0.6) active layer only exhibited a good PCE of 9.92%. More importantly, the siloxane-functionalized side chains increase the light-absorption ability, carrier mobility, blend miscibility, and film morphology in ternary devices compared to those of the binary devices. Hence, exciton dissociation, charge carrier transport, and suppressed recombination properties were facilitated. In the presence of Si-BDT, both binary and ternary all-PSCs PCEs are significantly improved. Indeed, 13.45% PCE is one of the best values reported for all-PSCs except for those based on polymerized small molecule acceptors. In addition, the ternary all-PSCs showed excellent environmental and thermal stabilities with 95 and 84% of the initial PCE retained after 900 and 500 h, respectively. These results offer effective device engineering, providing a new avenue for improving the device performance in ternary all-PSCs.

All-Polymer Solar Cells Approaching 12% Efficiency with a New π-Conjugated Polymer Donor Enabled by a Nonhalogenated Solvent Process.

High efficiency and nonhalogenated solvent processing are important issues for commercial application of all-polymer solar cells (all-PSCs). In this regard, we increased the photovoltaic performance of all-PSCs to a benchmark power conversion efficiency (PCE) of 11.66% by manipulating the pre-aggregation of a new π-conjugated polymer donor (Nap-SiBTz) using toluene as a solvent. This use of Nap-SiBTz enhanced the absorption coefficient (λmax = 9.30 × 104 cm-1), increased charge carrier mobility, suppressed trap-assisted recombination, improved bulk heterojunction morphology, and resulted in high PCEs of all-PSCs with an active layer thickness of 200 nm. To overcome severe charge recombination and energy losses, a 1-phenylnapthalene additive was used to achieve a well-ordered microstructure and molecular packing that inherently improved the device performances. The resulting encapsulation-free devices exhibited good ambient and thermal stabilities. The results of this study augur well for the future of the roll-to-roll production of all-PSCs.

External Quantum Efficiency Exceeding 24% with CIEy Value of 0.08 using a Novel Carbene-Based Iridium Complex in Deep-Blue Phosphorescent Organic Light-Emitting Diodes.

Deep-blue triplet emitters remain far inferior to standard red and green triplet emitters in terms of exhibiting high-color-purity Commission International de l'Éclairage (CIE) y values of ≤0.1, external quantum efficiencies (EQEs), and high electroluminescent brightnesses in phosphorescent organic light-emitting diodes. In fact, no deep-blue triplet emitter with color purity and high device performance has previously been reported. In this study, a deep-blue triplet emitter, mer-tris(N-phenyl, N-benzyl-pyridoimidazol-2-yl)iridium(III) (mer-Ir1) is developed, which meets the requirements of the National Television System Committee (NTSC) CIE(x, y) coordinates of (0.149, 0.085) with an extremely high EQE of 24.8% and maximum brightness (Lmax ) of 6453 cd m-2 , by a device with a 40 vol% doping ratio. Moreover, another device demonstrates an EQEmax of 21.3%, an Lmax of 5247 cd m-2 , and CIE(x, y) coordinates of (0.151, 0.086) at a 30 vol% doping ratio. This is the first report of a high-performance, deep-blue phosphor, carbene-based Ir(III) complex device with outstanding CIE(x, y) color coordinates and a high EQE. The results of this study indicate that the novel dopant mer-Ir1 is a promising candidate for reducing power consumption in display applications.

An Efficient Amphiphilic-Type Triphenylamine-Based Organic Hole Transport Material for High-Performance and Ambient-Stable Dopant-Free Perovskite and Organic Solar Cells.

A new set of simply structured triphenylamine-based small molecules are synthesized and evaluated as dopant-free hole transporting materials (HTMs) for high-performance perovskite solar cells (PSCs) and bulk heterojunction inverted organic solar cells (BHJ IOSCs). Surprisingly, the new amphiphilic-type HTM-1 (with internal hydrophilic groups and peripheral hydrophobic alkyl tails) showed better compatibility and performance than the actual target molecule, that is, HTM-2 in PSCs and BHJ IOSCs. Importantly, the HTM-1-based dopant-free PSCs and BHJ IOSCs exhibited high power conversion efficiencies (PCEs) of 11.45 % and 8.34 %, respectively. These performances are superior and comparable to those of standard HTMs Spiro-OMeTAD (2,2',7,7'-tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene)/polystyrene sulfonate) in PSCs and BHJ IOSCs, respectively. The enhanced device performance of the HTM-1-based PSCs is ascribed to its strong affinity towards the perovskite, properly aligned energy levels with respect to the perovskite valence band, and excellent hole transporting behavior. In addition, the well-organized energy levels of the HTMs showed excellent compatibility in BHJ IOSCs. The new amphiphilic-type HTM-based photovoltaic devices also showed long-term air stability over 700 h. These promising results offer new and unexpected prospects for engineering the interface between the photoactive material and HTMs in PSCs and BHJ IOSCs.

Achieving Pure Deep-Blue Electroluminescence with CIE y≤0.06 via a Rational Design Approach for Highly Efficient Non-Doped Solution-Processed Organic Light-Emitting Diodes.

Deep-blue fluorescent emitters with Commission Internationale de l'Eclairage (CIE) y≤0.06 are urgently needed for high-density storage, full-color displays and solid-state lighting. However, developing such emitters with high color purity and efficiency in solution-processable non-doped organic light-emitting diodes (OLEDs) remains an important challenge. Here, we present the synthesis of two new deep-blue fluorescent emitters (AFpTPI and AFmTPI) based on 10-(9,9-diethyl-9H-fluoren-2-yl)-9,9-dimethyl-9,10-dihydroacridine as a core and 1,3- and/or 1,4-phenylene-linked triphenylimidazole (TPI) analogues for non-doped solution-processable OLEDs. Their thermal, photophysical, electrochemical, and device characteristics are explored, and also strongly supported by density functional theory (DFT) study. AFpTPI and AFmTPI exhibit excellent thermal stability (≈450 °C) with high glass transition temperatures (Tg ; 141-152 °C) and deep-blue emission with high quantum yields. Specifically, the solution-processed non-doped device with AFpTPI as an emitter exhibits a maximum external quantum efficiency (EQE) of 4.56 % with CIE coordinates of (0.15, 0.06), which exactly matches the European Broadcasting Union (EBU) blue standard. In addition, AFmTPI also displays good efficiency and better color purity (EQE: 3.37 %; CIE (0.15, 0.05)). To the best of our knowledge, the present work is the first report on non-doped solution-processable OLEDs with efficiency close to 5 % and CIE y≤0.06.

Highly Efficient Organic Hole Transporting Materials for Perovskite and Organic Solar Cells with Long-Term Stability.

Small molecules based on N-atom-linked phenylcarbazole-fluorene as the main scaffold, end-capped with spirobifluorene derivatives, are developed as organic hole-transporting materials for highly efficient perovskite solar cells (PSCs) and bulk heterojunction (BHJ) inverted organic solar cells (IOSCs). The CzPAF-SBF-based devices show remarkable device performance with excellent long-term stability in PSCs and BHJ IOSCs with a maximum PCE of 17.21% and 7.93%, respectively.