Han Young Woo

Organic solar cells (OSCs) based on oligomer acceptors have garnered significant interest for their notable power conversion efficiency (PCE) and enduring stability. Despite their great potential, the development of oligomer acceptors remains behind traditional small molecule acceptors (SMA) -based systems, primarily due to a scarcity of effective oligomer materials. To address this gap, our study introduces a novel hybrid synthesis strategy for oligomer acceptors, integrating two distinct acceptor units. We synthesize the heterotrimer acceptor TQT and the single-acceptor-unit oligomers Tri-BT and Tri-Qx to assess the impact of our approach on OSC performance and durability. Notably, the crystallinity of the hybrid molecule TQT is significantly enhanced compared to the other two molecules. Consequently, the PCE of the PM6:TQT OSC reached 18.52%, marking the highest efficiency observed in OSCs composed of …

Semi‐transparent organic solar cells (ST‐OSCs) possess significant potential for applications in vehicles and buildings due to their distinctive visual transparency. Conventional device engineering strategies are typically used to optimize photon selection and utilization at the expense of power conversion efficiency (PCE); moreover, the fixed spectral utilization range always impose an unsatisfactory upper limit to its light utilization efficiency (LUE). In this study, a novel solid additive 1,3‐diphenoxybenzene (DB) has been employed to dual‐regulate donor/acceptor molecular aggregation and crystallinity, which effectively broadens the spectral response of resulting device in near‐infrared region. Besides, more visible light was allowed to pass through the devices, which enables ST‐OSCs to possess satisfactory photocurrent and high average visible transmittance (AVT) simultaneously. The inclusion of DB also …

Series of bulk heterojunction (BHJ) and layer‐by‐layer (LbL) all‐polymer solar cells (APSCs) were prepared with polymer PM6 as donor and polymer PY‐DT as acceptor based on conventional and inverted configuration. Benefiting from the sequential deposition strategy, the good vertical phase separation and more ordered molecular arrangement can be formed in the LbL APSCs. The conventional LbL APSCs exhibit an optimized power conversion efficiency (PCE) of 17.24% with a relatively large short circuit current density of 23.83 mA cm−2 and fill factor of 74.60%, photogenerated excitons near the indium tin oxide electrode can be efficiently utilized through energy transfer from PM6 to PY‐DT and the self‐absorption effect of PM6 for its long exciton diffuse distance. The 17.24% PCE of conventional LbL APSCs is higher than 16.72% of conventional BHJ APSCs, 14.59% of inverted BHJ APSCs and 12.41% of …

Eco-friendly solution processing and the low-cost synthesis of photoactive materials are important requirements for the commercialization of organic solar cells (OSCs). Although varieties of aqueous-soluble acceptors have been developed, the availability of aqueous-processable polymer donors remains quite limited. In particular, the generally shallow highest occupied molecular orbital (HOMO) energy levels of existing polymer donors limit further increases in the power conversion efficiency (PCE). Here, we design and synthesize two water/alcohol-processable polymer donors, poly[(thiophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-T)) and poly[(selenophene-2,5-diyl)-alt-(2-((13-(2,5,8,11-tetraoxadodecyl)-2,5,8,11-tetraoxatetradecan-14-yl)oxy)-6,7-difluoroquinoxaline-5,8-diyl)] (P(Qx8O-Se)) with oligo(ethylene glycol) (OEG …

Ideal nanoscale morphology of heterojunction active layer is important for the development of organic solar cells (OSCs). However, the mismatched crystalline kinetic between the polymer donor and small molecular acceptor often leads to the difficulties in controlling the morphology of the active layer. Herein, polar 1,2‐dibromo‐4,5‐difluorobenzene (DFB) and non‐polar 1,4‐dibromotetrafluorobenzene (TFB) are developed as the volatile additives for OSCs. More attractively, different from the reported volatile additives, both new volatile additives can simultaneously interact with donor and acceptor, synergistic regulating the crystallization kinetic and well‐balancing the crystallization behaviors between the polymer donor and small molecular acceptor during film formation process. Notably, due to the stronger dipole‐dipole interactions with active layer, polar DFB induces the more favorable film morphology than non …

n-Type polymer semiconductors are essential for enabling high-performance organic electronic devices; however, their development still remains a challenge. Herein, we reported a new electron-deficient building block, i.e. bithiophene imide (BTI)-bridged isoindigo (IID), BTIID, through a Knoevenagel condensation reaction between the bisaldehyde BTI and the alkylated indolinones. Three donor-acceptor (D-A) copolymers were then successfully synthesized via standard Stille coupling reaction based on this novel building block, which exhibit highly planar backbones and low-lying lowest unoccupied molecular orbitals (LUMO) energy levels. When integrated into organic field-effect transistors (OFETs), these polymers demonstrated unipolar n-type transport characteristics with a highest electron mobility of 5.79 × 10−4 cm2 V−1 s−1. Our research results indicate that the design of strong electron-withdrawing units …

Most top‐rank organic solar cells (OSCs) are manufactured by the halogenated solvent chloroform, which possesses a narrow processing window due to its low‐boiling point. Herein, based on two high‐boiling solvents, halogenated solvent chlorobenzene (CB) and non‐halogenated green solvent ortho‐xylene (OX), preparing active layers with the hot solution is put forward to enhance the performance of the OSCs. In situ test and morphological characterization clarify that the hot‐casting strategy assists in the fast and synchronous molecular assembly of both donor and acceptor in the active layer, contributing to preferable donor/acceptor ratio, vertical phase separation, and molecular stacking, which is beneficial to charge generation and extraction. Based on the PM6:BO‐4Cl, the hot‐casting OSCs with a wide processing window achieve efficiencies of 18.03% in CB and 18.12% in OX, which are much higher than …

Synaptic devices have gained prominence as viable alternatives to conventional complementary metal‐oxide‐semiconductor‐based (CMOS) electronics in the information processing field owing to their inherent advantages in analog and parallel operations. The potential of synaptic devices has not yet been fully utilized for logic operations because only the conventional binary logic structure has been applied to analog synaptic devices, leading to the loss of advantages unique to analog signals. To resolve this issue, an innovative concept is proposed: an analog logic gate that can perform parallel operations at the device level and is coupled with logic reconfigurations, enabling comprehensive analog computation. This logic gate comprises two synaptic devices with different retention characteristics, adjusted by the side‐chain engineering of an organic polymer. The long‐term and short‐term synaptic devices …

The unprecedented development of all‐polymer solar cells (all‐PSCs) is hindered by their low short‐circuit current density (Jsc), mainly due to the absence of near‐infrared (NIR) polymer acceptor materials. To tackle this challenge, a molecular design principle is proposed, which involves the regulation of steric hindrance on the fused‐ring backbone to obtain NIR polymer acceptors. Accordingly, three acceptors named PTz‐Ph, PTz‐Me, and PTz‐H are synthesized by substituting the Phenyl, Methyl, and Hydrogen in the beta position of the thiophene unit based on fused‐ring molecules. Different from the necessity of steric hindrance of small molecule acceptors in achieving an outstanding performance, polymer acceptor PTz‐H without steric hindrance‐substitution achieves a record‐high efficiency for the benzotriazole‐based all‐PSCs. Then, introducing PTz‐H into the binary PBDB‐T:PTz‐BO system, the ternary all …

High‐performance n‐type polymeric mixed ionic‐electronic conductors (PMIECs) are essential for realizing organic electrochemical transistors (OECTs)‐based low‐power complementary circuits and biosensors, but their development still remains a great challenge. Herein, by devising two novel n‐type polymers (f‐BTI2g‐SVSCN and f‐BSeI2g‐SVSCN) containing varying selenophene contents together with their thiophene‐based counterpart as the control, it is demonstrated that gradually increasing selenophene loading in polymer backbones can simultaneously yield lowered lowest unoccupied molecular orbital levels, boosted charge‐transport properties, and improved ion‐uptake capabilities. Therefore, a remarkable volumetric capacitance (C*) of 387.2 F cm−3 and a state‐of‐the‐art OECT electron mobility (µe,OECT) of 0.48 cm2 V−1 s−1 are synchronously achieved for f‐BSeI2g‐SVSCN having the highest …

Single-entity electrochemistry (SEE) was used to investigate the stochastic collisions of polymeric entities. Electrocatalytic amplification of π-conjugated polyelectrolytes (CPEs) using the oxidation of ammonia borane (AB) was employed for detecting polymeric entities. AB oxidation, while slow on a carbon ultramicroelectrode (C-UME), is catalyzed by the active sites of CPEs, which have positive polarons formed along their backbone owing to collisions with the electrode at a sufficiently positive potential (+0.5 V). The collision frequency of the CPE was proportional to the increase in concentration, and the charge distribution of particle collisions tended to be similar to the size distribution obtained by dynamic light scattering (DLS). By applying this method in combination with optical techniques, additional information can be obtained at the molecular level, thereby contributing to the fields of biosensors, and solar/fuel …

Developing low‐cost and high‐performance n‐type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron‐deficient building blocks with simple structure and easy synthesis, which are essential for the development of n‐type polymer semiconductors. Herein, we synthesized two cyano‐functionalized highly electron‐deficient building blocks, namely 3,6‐dibromopyrazine‐2‐carbonitrile (CNPz) and 3,6‐Dibromopyrazine‐2,5‐dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one‐step reaction and three‐step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor‐acceptor (A‐A) polymers, P(DPP‐CNPz) and P(DPP‐DCNPz) are successfully developed, featuring deep‐positioned lowest unoccupied …

The effective reduction of dark (or noise) current presents a significant hurdle in enhancing the detectivity of organic photodetectors (OPDs). To address this challenge, a photo-crosslinkable donor polymer, PM6-Br50, is synthesized by introducing bromoalkyl side-chains onto the PM6 structure. This modification enables the formation of a pseudo planar heterojunction (p-PHJ) structure of crosslinked donor/acceptor through a layer-by-layer (LbL) sequential process without the necessity for an semi-orthogonal solvent. This innovation effectively overcomes solvent-related limitations in the LbL process. Additionally, we replace the semi-metallic hole-transport layer (HTL), PEDOT:PSS, with a semiconducting conjugated polyelectrolyte (TPAFS-TMA) with a high conduction band. The p-PHJ configuration, featuring pure donor/anode and pure acceptor/cathode contacts, enhances the charge injection barrier for electrons …

As a notable analogue of benzo[1,2-b:4,5-b′]dithiophene (BDT), dithieno[2,3-d:2′,3′-d′]benzo[1,2-b:4,5-b′]dithiophene (DTBDT) is expected to be a more promising building block for polymer photovoltaic donor materials due to its larger coplanar core and extended conjugation length as well as a similar electron donor ability to BDT. However, the performance of organic solar cells (OSCs) from DTBDT-based copolymers is much lower than that of OSCs from BDT-based copolymers, which is attributed to the higher voltage loss of the OSCs from DTBDT-based polymers as compared to that from BDT-based polymers. In this study, approaches such as increasing the donor (D) and acceptor (A) spacing by lengthening the side chains of the polymer donors and use of radical conjugated polymer additives are synergistically employed in OSCs from 2-alkyl-3-chlorothiophene flanked DTBDT-alt-1,3-bis(thiophen-2-yl …

Photomultiplication type organic photodetectors (PM‐OPDs) exhibit obvious superiority in weak light detection due to their low dark current density (JD) and large photo‐induced current density (JPI). The JD is one of the important parameters that influences light detection sensitivity of PM‐OPDs, how to effectively suppress the JD is a great challenge to improve the performance of PM‐OPDs. In this work, the JD of PM‐OPDs can be suppressed by employing PTAA or doped‐PTAA as the interfacial layer replacing PEDOT:PSS layer. The PM‐OPDs with PTAA layer exhibit a low JD of 2.3 × 10−7 A cm−2 under −6 V bias, which is much smaller than 1.4 × 10−6 A cm−2 for PM‐OPDs with PEDOT:PSS layer. The small molecule DRCN5T is incorporated into PTAA to further passivate surficial defects of PTAA films, which is conducive to reducing the leakage current of PM‐OPDs. The optimal PM‐OPDs exhibit rather low JD …

Developing polymers with high electrical conductivity (σ) after n‐doping is a great challenge for the advance of the field of organic thermoelectrics (OTEs). Herein, we report a series of thiazole imide‐based n‐type polymers by gradually increasing selenophene content in polymeric backbone. Thanks to the strong intramolecular noncovalent N⋅⋅⋅S interaction and enhanced intermolecular Se⋅⋅⋅Se interaction, with the increase of selenophene content, the polymers show gradually lowered LUMOs, more planar backbone, and improved film crystallinity versus the selenophene‐free analogue. Consequently, polymer PDTzSI−Se with the highest selenophene content achieves a champion σ of 164.0 S cm−1 and a power factor of 49.0 μW m−1 K−2 in the series when applied in OTEs after n‐doping. The σ value is the highest one for n‐type donor‐acceptor OTE materials reported to date. Our work indicates that …

Multiple‐resonance thermally activated delayed fluorescence (MR‐TADF) emitters exhibit enormous potential for use in organic light‐emitting diodes (OLEDs), owing to their exceptional external quantum efficiencies (EQEs) and narrowband emission spectra. However, planar MR‐TADF emitters often suffer from aggregation‐caused quenching (ACQ) and spectral broadening at high doping concentrations because of strong interchromophore π–π interactions. A method of sterically encapsulating the planar MR skeleton with four bulky 9‐phenyl‐fluorene (Fl) units is devised, resulting in the development of a bright bluish‐green emitter (4FlCzBN). This steric shielding effectively reduces intermolecular interactions, suppresses ACQ, and improves solubility. Consequently, by utilizing 4FlCzBN as a doping‐insensitive MR emitter, solution‐processed OLEDs are fabricated with doping concentrations of 2–16 wt.%, and …

We explore the application of a high conduction band polymer acceptor (IDSIC-BTI) as a ternary component in indoor organic photovoltaic cells (IOPVs) and organic photodiodes (OPDs). IDSIC-BTI shows a 1.91 eV electrochemical band gap and a high-lying lowest unoccupied molecular orbital (LUMO) of −3.78 eV. Its compatibility and miscibility with nonfullerene acceptors (NFAs) stem from shared electron-deficient structural elements. Combining IDSIC-BTI with NFAs such as IT-4F and Y6 yields smooth surface morphologies and elevates LUMO levels due to the formation of acceptor–acceptor (A–A) alloys. This heightened LUMO level within the A–A alloy structure contributes to the expansion of the energy gap associated with charge-transfer states (ECT) in ternary blends using PM6 as a donor polymer. As a direct consequence of this effect, these ternary blends exhibit an increased open-circuit voltage (VOC …

The thin film deposition engineering of layer‐by‐layer (LbL) non‐fullerene organic solar cells (OSCs) favors vertical phase distributions of donor:acceptor (D:A), effectively boosting the power conversion efficiency (PCE). However, previous deposition strategies mainly aimed at optimizing the morphology of LbL films, and paid limited attention to the reproducibility of device performance. To achieve high device performance and maintain reproducibility, a strategy for hierarchical morphology manipulation in LbL OSCs is developed. A series of LbL devices are fabricated by introducing vacuum‐assisted molecular drift treatment (VMDT) to the donor or acceptor layer individually or simultaneously to elucidate the functionalities of this treatment. Essentially, the VMDT provides an extended drift driving force to manipulate the donor and acceptor molecules, resulting in a well‐defined vertical phase distribution and ordered …

High‐performing n‐type polymers are crucial for the advance of organic electronics field, however strong electron‐deficient building blocks with optimized physicochemical properties for constructing them are still limited. The imide‐functionalized polycyclic aromatic hydrocarbons (PAHs) with extended π‐conjugated framework, high electron deficiency and good solubility serve as promising candidates for developing high‐performance n‐type polymers. Among the PAHs, phenanthrene (PhA) features a well‐delocalized aromatic π‐system with multiple modifiable active sites . However, the PhA‐based imides are seldom studied, mainly attributed to the synthetic challenge. Herein, we report two functionalized PhAs, CPOI and CPCNI, by simultaneously incorporating imide with carbonyl or dicyanomethylene onto PhA. Notably, the dicyanomethylene‐modified CPCNI exhibits a well stabilized LUMO energy level (−3 …