Charge Transport Research Articles

Investigating Molecular Junctions Based on Mixed Self-Assembled Monolayers to Understand the Impact of Intermolecular Interactions on Transport.

To interrogate the importance of intermolecular interactions on charge transport at the nanoscale, we investigate molecular tunnel junctions based on mixed self-assembled monolayers (SAMs) of 1-alkyl (CnT) thiols and their fluorinated counterparts (F-CnT) that have substantially different tunneling conductances. Experiments on mixed CnT1-x:F-CnTx SAMs between Au contacts reveal a strongly nonlinear (exponential) dependence of the tunneling conductance G on composition x, a behavior that is tempting to assign to the strong impact of intra-SAM intermolecular interactions. However, analysis suggests that the exponential dependence of G on x does not arise from intra-SAM intermolecular interactions, but instead emerges from the work function modification of the Au electrode which varies linearly with x.

Electrophoretic deposition of carbon-ionomer layers on proton conducting membranes.

Synthetic and natural carbons are widely used as carrier for electrodes in electrochemical applications. They need to have a controlled morphology in order to facilitate mass and charge transport, so the process of film formation is of uttermost importance. Here we show, how carbons (after proper preconditioning) can be codeposited with an ionomer by electrophoretic deposition, a method that does allow full control of deposition conditions during the process. In view of potential applications, we focus on the direct deposition on proton-conducting membranes. Ionomers and membranes applied are based on established per-fluorinated polyethylene with SO3H-terminated side chains (PFSA). Conditions for reproducible deposition are reported in terms of optimal charge on the carbon particles, field strength in the deposition cell and necessary deposition times for a given film thickness. Additionally, a horizontal cell arrangement is suggested to avoid gravitational effects.

Bi2Te3/Carbon Nanotube Hybrid Nanomaterials as Catalysts for Thermoelectric Hydrogen Peroxide Generation

Harnessing waste heat from environmental or industrial sources presents a promising approach to eco-friendly and sustainable chemical synthesis. In this study, we introduce a thermoelectrocatalytic (TECatal) system capable of utilizing even small amounts of heat for hydrogen peroxide (H2O2) production. We developed a nanohybrid structure, combining carbon nanotubes (CNTs) and Bi2Te3 nanoflakes (Bi2Te3/CNTs), through a one-pot synthesis method. Bi2Te3, as a thermoelectric (TE) material, generates charge carriers under a temperature gradient via the Seebeck effect, enabling them to participate in surface redox reactions. However, the rapid recombination of these charge carriers greatly limits the TECatal activity. In the Bi2Te3/CNTs nanohybrid system, the introduction of CNTs substantially enhances the efficiency of H2O2 production, as the strong bonding between CNTs and Bi2Te3, along with the excellent conductivity of CNTs, facilitates charge carrier separation and transport, as confirmed by TE electrochemical tests. This study underscores the significant potential of thermoelectric nanomaterials for converting waste heat into green chemical synthesis.

Ethanol Processable Inorganic‐Organic Hybrid Hole Transporting Layers Enabled 20.12 % Efficiency Organic Solar Cells

AbstractIn this study, a high‐performance inorganic‐organic hybrid hole transporting layer (HTL) was developed using ethanol‐soluble alkoxide precursors and a self‐assembled monolayer (SAM). Three metal oxides‐vanadium oxide (VOx), niobium oxide (Nb2O5), and tantalum oxide (Ta2O5)‐were synthesized through successive low‐temperature (100 °C) thermal annealing (TA) and UV‐ozone (UVO) treatments of their respective precursors: vanadium oxytriethoxide (EtO−V), niobium ethoxide (EtO−Nb), and tantalum ethoxide (EtO−Ta). Among these, the Nb2O5 film exhibited excellent transmittance, a high work function, and good conductivity, along with a more compact and uniform structure featuring fewer interfacial defects, which facilitated efficient charge extraction and transport. Furthermore, the deposition of a SAM of (2‐(9H‐carbazol‐9‐yl)ethyl)phosphonic acid (2PACz) on top of Nb2O5 further passivated defects, enhancing interfacial contact with the photoactive layer. The resulting inorganic‐organic hybrid HTL of Nb2O5/2PACz demonstrated excellent compatibility with various photoactive blends, achieving impressive power conversion efficiencies of 19.44 %, 19.18 %, and 20.12 % for the PM6:L8‐BO, PM6:BTP‐eC9, and D18:BTP‐eC9 based organic solar cells, respectively. 20.12 % is the best performance for bulk heterojunction organic solar cells with binary components as the photoactive layer.

Fe−N Co‐Doped BiVO4 Photoanode with Record Photocurrent for Water Oxidation

AbstractBismuth vanadate (BVO) ranks among the most promising photoanodes for photoelectrochemical (PEC) water splitting. Nonetheless, slow charge separation and transport, besides the sluggish water oxidation kinetics, are key barriers to its photoefficiency. Here, we present a co‐doping strategy that significantly improves the charge separation performance of BVO photoanodes. We found that, under standard one sun illumination, the Fe−N co‐doped BVO photoanode (Fe−N−BVO) by N‐coordinated Fe precursor reaches a record photocurrent density of 7.01 mA cm−2 at 1.23 V vs RHE after modified a surface co‐catalyst (FeNiOOH), and exhibits an outstanding stability. By contrast, much lower photocurrent density is obtained for the N‐doped, Fe‐doped and Fe/N‐doped BVO photoanode with separated N and Fe precursors. The detailed experimental characterizations show that the high activity of the Fe−N co‐doped BVO photoanode is attributed to the enhanced photo‐induced bulk charge separation, as well as the accelerated surface water oxidation kinetics. XPS, EXAFS and DFT calculations clearly show that, instead of formation of deep trapping state in the individually doped BVO, the co‐doping of Fe−N into BVO generates Fe‐based electronic states just below the bottom of conduction band and N‐derived states just above the top of valence band. Such modulations in electronic structure enable the efficient trap of the electrons and holes to enhance the separation of photo‐induced carriers, but hinder the charge recombination originated from the deep trapping sites.

A semiconducting supramolecular Co(II)-metallogel based resistive random access memory (RRAM) design with good endurance capabilities.

A highly efficient approach for synthesizing a supramolecular metallogel of Co(II) ions, denoted as CoA-TA, has been established under room temperature and atmospheric pressure conditions. This method employs the metal-coordinating organic ligand benzene-1,3,5-tricarboxylic acid as a low molecular weight gelator (LMWG) in DMF solvent. A comprehensive analysis of the mechanical properties of the resulting supramolecular Co(II)-metallogel was conducted through rheological investigation, considering angular frequency and thixotropic study. The hierarchical rocky network structure of the supramolecular Co(II)-metallogel was unveiled using field emission scanning electron microscopy (FESEM). Transmission electron microscopic (TEM) analysis showed rod-shaped structures via low-magnification high angle annular dark field (HAADF) bright field scanning transmission electron microscopic (STEM) imaging, while energy dispersive X-ray (EDX) elemental mapping confirmed its primary chemical constituents. The formation mechanism of the metallogel was examined via fourier transform infrared spectroscopy (FTIR) spectroscopy. The nature of the synthesized CoA-TA metallogel was affirmed through powder X-ray diffraction (PXRD) analysis. Furthermore, this study involved fabrication of Schottky diode structures in a metal-semiconductor-metal geometry based on cobalt(II) metallogel (CoA-TA), enabling observation of charge transport behavior. Remarkably, a resistive random access memory (RRAM) device utilizing cobalt(II) metallohydrogel (CoA-TA) demonstrated bipolar resistive switching at room temperature and under ambient conditions. The switching mechanism was investigated, revealing the formation and rupture of conductive filaments between metal electrodes that govern the resistive switching behavior. This RRAM device exhibited an impressive ON/OFF ratio (~ 414) and exceptional endurance over 5000 switching cycles. These structures offer great potential for diverse applications such as non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics. Their advantages lie in their fabrication process, reliable resistive switching behavior and overall performance stability.

Terminal Fluorination Modulates Crystallinity and Aggregation of Fully Non‐Fused Ring Electron Acceptors for High‐Performance and Durable Near‐Infrared Organic Photodetectors

High dark current density (Jd) severely hinders further advancement of near‐infrared organic photodetectors (NIR OPDs). Herein, we tackle this grand challenge by regulating molecular crystallinity and aggregation of fully non‐fused ring electron acceptors (FNREAs). In contrast to the general trend in terminal halogenation of electron acceptors, TBT‐V‐F, featuring fluorinated terminals, notably demonstrates crystalline intensification and a higher prevalence predominance of J‐aggregate compared to its chlorinated counterpart (TBT‐V‐Cl). The amalgamation of advantages confers TBT‐V‐F‐based OPDs with more organized active layer morphology and denser molecular packing, resulting in improved charge transport, decreased energetic disorder, and reduced trap density. Consequently, the corresponding self‐powered OPDs exhibit a 40‐fold decrease in Jd, a remarkable increase in detectivity (D*sh), faster response time, and superior thermal stability compared to TBT‐V‐Cl‐based OPDs. Further interfacial optimization results in an ultra‐low Jd of 7.30´10‐12 A cm‐2 with D*sh over 1013 Jones in 320‐920 nm wavelength and a climax of 2.2´1014 Jones at 800 nm for the TBT‐V‐F‐based OPDs, representing one of the best results reported to date. This work paves a compelling material‐based strategy to suppress Jd for highly sensitive NIR OPDs, while also illustrates the viability of FNREAs in construction of stable and affordable NIR OPDs for real‐world applications.

Electrical Characterization of a Large‐Area Single‐Layer Cu3BHT 2D Conjugated Coordination Polymer

AbstractUnderstanding charge transport properties of large‐area single‐layer 2D materials is crucial for the future development of novel optoelectronic devices. In this work, the synthesis and electrical characterization of large‐area single‐layers of Cu3BHT 2D conjugated coordination polymers are reported. The Cu3BHT are synthesized on the water surface by the Langmuir‐Blodgett method and then transferred to SiO2/Si substrates with pre‐patterned electrical contacts. Electrical measurements revealed ohmic responses across areas up to ≈1 cm2, with a mean resistance of approximately 53 ± 3 kΩ at a probe separation of 50 µm. Cooling and heating cycles show hysteresis in the electrical response, suggesting different current pathways are formed as the samples underwent structural‐chemical changes during temperature sweeps. This hysteresis vanished after several cycles and the conductivity shows a stable exponential behavior as a function of temperature, suggesting that a temperature‐dependent tunneling process is governing the conduction mechanism in the analyzed polycrystalline single‐layer Cu3BHT samples. These results, together with density functional theory calculations and valence band X‐ray photoelectron spectroscopy data suggest that the single‐layer samples exhibit a semiconducting rather than a metallic behavior.

Design and Synthesis of Multipath Compact Cyclophanes for Quantum Interference Studies

To investigate interference phenomena and con­duc­tance properties in mechanically controlled break junctions (MCBJs), macrocycles 1 and 2 (BMCs: for BenzeneMacroCycles), containing a meta‐substituted benzene moiety with solubilizing tert‐butyl groups, as well as structures 3 and 4 (TMCs: for ThiopheneMacroCycles), featuring 2,5‐connected 3,4‐hexyl‐thio­phene corners, were synthesized. Macrocycles 1 and 2 respect­ively 3 and 4 differ in the positions of the acetyl‐protected sulfur anchoring groups, which impacts both, the individual transport efficiency of their parallel electronic pathways and their overall molecular wire lengths. All macrocycles were synthesized based on a series of Sonogashira cross‐coupling reactions. For 3 and 4, a 2‐(4‐pyridin­yl)ethyl protecting group for the sulfur atoms was successful, while for macrocycles 1 and 2 the more common tert‐butyl protecting group did the job. To our delight, proof‐of‐concept charge transport studies conducted in an MCBJ setup demon­strated the expected trends regarding improved conductance intensities for the TMCs compared to the BMCs. Furthermore, the corres­ponding molecular plateaus from the breaking experiments were in the expected length range of the S‐S distances for all compounds. We also found that the overall conductance seems to follow a more complex transport mechanism than just the sum of contributions from both channels.

Impact of Tetrakis(dimethylamido)tin(IV) Degradation on Atomic Layer Deposition of Tin Oxide Films and Perovskite Solar Cells.

Tin oxide (SnOx) films synthesized by atomic layer deposition (ALD) are widely explored in a range of optoelectronic devices including electrochemical sensors, transistors, and photovoltaics. However, the integrity of the key ALD-SnOx precursor, namely tetrakis(dimethylamido)tin (IV) (TDMASn), and its influence on the properties of ultimate films remain unexplored. Here a significant degradation of TDMASn into bis(dimethylamido)tin(II) via the Sn-imine complex is reported, and its impact on the corresponding films and devices is examined. It is found, surprisingly, that this degradation does not affect the growth kinetics and morphology of ALD-SnOx films. But it notably deteriorates their electronic properties, resulting in films with twice the electrical resistance due to different oxidation mechanisms of the degradation products. Perovskite solar cells employing such films exhibit a significant loss in power conversion efficiency, primarily due to charge transport and transfer losses. These findings urge strategies to stabilize TDMASn, a critical precursor for ALD-SnOx films, or to identify alternative materials to achieve efficient and reliable devices.

Hexafluoroisopropanol modified MXene for perovskite surface remodeling and interfacial dipole effect enhancement

The development of high-efficiency and stable perovskite (PVK) solar cells (PSCs) still faces the challenge of non-ideal interfaces between PVK and charge transport layers. Herein, the hexafluoroisopropanol (HFIP) modified two-dimensional Ti3C2Tx MXene is custom-made (MX-HFIP) and employed as the interlayer between the PVK and hole transport layer (HTL) interface by forming hydrogen bonds. The MX-HFIP serves to reinforce the interface contact and remodel the surface of PVK, leading to a high-quality PVK film with a significantly reduced defect density, suppressed nonradiative recombination, and inhibited invasion of water and oxygen. Moreover, the synergistic effect of MXene and HFIP results in an enhanced interfacial dipole effect and an optimized energy-level alignment, thereby increasing the driving force for charge extraction and transport at the PVK/HTL interface. Therefore, the MX-HFIP treated PSC achieves a substantially-enhanced power conversion efficiency (PCE) of 22.33 %, as compared to 20.05 % of the untreated device. Besides, the MX-HFIP treated PSC delivers significantly enhanced stabilities, with 88 % of its initial PCE after 1656 h of storage at 25 °C under 30 %⁓40 % relative humidity. These findings demonstrate the advancement using fluorine-rich molecule modified MXene to improve interfacial properties for enhancing performances and stabilities of optoelectronic devices.

A Facile Electrochemical Strategy for Achieving a High-Conductivity Polypyrrole Derivative with Intrinsic Metallic Transport as a High-Performance Electrochromic Conducting Polymer Film.

Conjugated polymer electrochromic materials (PECMs) with tailored optical and electrical properties are applied in smart windows, electronic displays, and adaptive camouflage. The limitation in the electrical conductivity results in slow and monotonous color switching. We present a polypyrrole film incorporated with a toluene-p-sulfonic group (PPy-TSO-F), via a one-step electrodeposition technique. The PPy-TSO-F thin film (110 nm) achieves an impressive electrical conductivity of 1011 S cm-1, a high carrier mobility of 82 cm2 V-1 s-1, and intrinsic metallic electronic behavior. It demonstrates exceptionally reversible multicolor switching, transitioning from emerald green (-1.5 V), to bluish green (-1.4 V), bright yellow (-1.2 V), greenish yellow (-0.6 V), reddish brown (0.1 V), dark brown (0.3 V), and atrovirens (0.6 V). The fast charge transport and high carrier mobility render the film with an ultrafast electrochromic switching speed of 0.01 s/0.02 s. This research provides a new route to designing ultrafast multicolor switching PECMs with metallic charge transport.

Informatics-based design of polyaniline-carbon nanotube thermoelectric nanocomposite using ANN and GA

Abstract Conducting polymer and carbon nanotube (CNT) based nanocomposites have emerged as prospective thermoelectric (TE) materials due to their potential application in flexible electronics. Non-conventional charge and heat transport in these nanocomposites, presents the possibility to enhance the TE conversion efficiency, given by ZT. However, the highly non-linear and complex association of structure and composition with the overall TE properties have hindered the development of any general strategy to develop high ZT nanocomposites. Here, we implement artificial neural network (ANN) and genetic algorithm (GA) to develop data driven models followed by optimization to design high efficiency nanocomposites based on CNT dispersed in polyaniline (PANI) matrix. Our models suggest that CNT concentration plays the most crucial role in determining ZT. Non-dominated Pareto optimal solutions consisting of different combinations of design variables are obtained by multi-objective optimization. Although a range of optimal solutions span over different regions of the search space, in general we note that longer CNTs boost Seebeck coefficient (S) and electrical conductivity (σ), and smaller length lowers thermal conductivity (k), while higher diameter of CNTs increase S and lowers σ and k. The results provide a general guideline for developing CNT-PANI nanocomposites with enhanced TE figure of merit.

Chemi-Impeditive Sensing Platform Based on Single-Walled Carbon Nanotubes.

Chemical sensing methodology based on electrochemical impedance spectroscopy (EIS) targeting analytes in aqueous samples on functionalized single-walled carbon nanotube (SWCNT) is reported. The SWCNT in contact with electrolyte shows unique impedance spectra that cannot be analyzed with classical equivalent circuit models. Inspired by the charge transport property of mixed ionic-electronic conductors, we propose an equivalent circuit based on transmission line model (TLM), by which the impedance of the CNT-electrolyte system can be analyzed to track down all the equivalent circuit parameters. By combining multiple pieces of information, which are technically immeasurable with conventional chemiresistive or chemicapacitive techniques, several analyte species responding to the sensor can be differentiated from each other. We demonstrate the "chemi-impeditive" concept on chemically modified SWCNTs for detecting perfluoroalkyl substances (PFAS) in aqueous solutions. The EIS coupled with a fluorination chemistry on SWCNT surface provides unique changes in equivalent circuit components for each PFAS, i.e., changes in CNT and solution resistances, as well as interfacial CNT-solution capacitance, through which perfluorooctanesulfonic acid, perfluorooctanoic acid, hexafluoropropylene oxide dimer acid, and perfluorobutanesulfonic acid are detected in a discriminative manner. The new impedimetric method opens up new vistas in chemical sensing in that the EIS analysis provides an additional dimension of information beyond the single resistance or capacitance typically measured by many conventional types of sensors.

Tunable Rectification in 2D Porphyrinic Metal–Organic Framework Nanosheets Molecular Heterojunctions

AbstractAs functional electrical devices advance, new strategies for regulating electrical properties are essential for achieving diverse electrical performance. In this study, molecular heterojunction rectifiers are constructed by connecting porphyrinic 2D metal–organic framework (2D MOF) nanosheets and oligophenylene thiols self‐assembled monolayers (OPT SAMs) within metal electrodes. The rectification characteristics can be tuned by the molecular length of OPT and the coordinated metal atom in the center of 2D MOFs. Specifically, a rectification ratio of more than 1.67 orders of magnitude is achieved in the heterojunction composed of 2D Zn‐TCPP MOF nanosheet (TCCP, tetrakis(4‐carboxyphenyl) porphyrin) and OPT3 SAM. Combining Kelvin probe force microscopy measurements and first‐principles calculations of the 2D MOF nanosheets, it elucidates that the rectification variations come from the adjustment of energy level alignment at OPT SAMs//2D MOF interface, leading to asymmetric charge transport with the voltage polarities. This strategy can be further extended to Cu‐MOF nanosheets, which also exhibit rectification behaviors when placed on OPT2 SAMs. This work provides a universal and flexible strategy for regulating the electrical behaviors of MOFs without the need for specific design and synthesis, paving the way for the development of MOF‐based functional electronic devices.

Thermoelectric properties of XX- and XY-stacked GeS/GeSe van der Waals heterostructures from DFT and BTP calculations.

This study utilizes density functional theory (DFT) and the Boltzmann transport equation (BTE) to investigate the structural, electronic, and thermoelectric properties of germanium sulfide (GeS) and germanium selenide (GeSe) monolayers, along with their van der Waals (vdW) heterostructures. We analyzed XX-stacked and XY-stacked configurations, where the XX configuration features direct atomic stacking, while the XY configuration exhibits staggered stacking. Our first-principles calculations indicate that the formation of GeS/GeSe heterostructures results in a reduction of bandgaps compared to their bulk and monolayer counterparts, yielding bandgap values of 0.91 eV for the XX configuration and 0.84 eV for the XY configuration. Stability assessments reveal that the XY configuration is more stable, demonstrating a lattice thermal conductivity of 15.21 W/mK compared to 17.95 W/mK for the XX configuration T 300 K. The thermoelectric properties were systematically evaluated across a temperature range of 300-800 K, revealing high Seebeck coefficients of 1.51 mV/K for the XX heterostructure and 1.39 mV/K for the XY heterostructure. reflecting their excellent charge transport capabilities. Notably, the figure of merit (ZT) at 800 K was calculated to be 0.90 for the XX configuration and 1.01 for the XY configuration, underscoring the superior thermoelectric performance of the XY heterostructure. These findings contribute to a comprehensive understanding of 2D GeS/GeSe heterostructures for thermoelectric applications and provide a solid foundation for future research and technological advancements in this domain.

Urea/Thiourea Imine Linkages Provide Accessible Holes in Flexible Covalent Organic Frameworks and Dominates Self‐Adaptivity and Exciton Dissociation

Unraveling the robust self‐adaptivity and minimal energy‐dissipation of soft reticular materials for environmental catalysis presents a compelling yet unexplored avenue. Herein, a top‐down strategy, tailoring from the unique linkage basis, flexibility degree, skeleton electronics to trace‐guest adaptability, is proposed to fill the understanding gap between micro‐soft covalent organic frameworks (COFs) and photocatalytic performance. The thio(urea)‐basis‐dominated linkage within benzotrithiophene‐based COFs induce the framework contraction/swelling (intralayer micro‐flexibility) in response to tetrahydrofuran or water. Adaptability of micro‐flexible thiourea‐COF with pore hydrophilicity not only contributes to the favorable mass transfer, but also enhances the accessible redox active sites, culminating in nearly 100% removal of micropollutant with low‐energy dissipation in wastewater. The incorporating urea/thiourea into imine linkage facilitates polarization reduction and exciton dissociation within skeleton wall, inducing strong localization for holes. This transformation facilitates interchain charge transport and unbalanced distribution conducive to oxidative holes‐mediated micropollutant decomposition.

Urea/Thiourea Imine Linkages Provide Accessible Holes in Flexible Covalent Organic Frameworks and Dominates Self-Adaptivity and Exciton Dissociation.

Unraveling the robust self-adaptivity and minimal energy-dissipation of soft reticular materials for environmental catalysis presents a compelling yet unexplored avenue. Herein, a top-down strategy, tailoring from the unique linkage basis, flexibility degree, skeleton electronics to trace-guest adaptability, is proposed to fill the understanding gap between micro-soft covalent organic frameworks (COFs) and photocatalytic performance. The thio(urea)-basis-dominated linkage within benzotrithiophene-based COFs induce the framework contraction/swelling (intralayer micro-flexibility) in response to tetrahydrofuran or water. Adaptability of micro-flexible thiourea-COF with pore hydrophilicity not only contributes to the favorable mass transfer, but also enhances the accessible redox active sites, culminating in nearly 100% removal of micropollutant with low-energy dissipation in wastewater. The incorporating urea/thiourea into imine linkage facilitates polarization reduction and exciton dissociation within skeleton wall, inducing strong localization for holes. This transformation facilitates interchain charge transport and unbalanced distribution conducive to oxidative holes-mediated micropollutant decomposition.

Surface n-Doped Metal Halide Perovskite for Efficient and Stable Solar Cells through Organic Chelation.

Perovskite solar cells (PSCs) have emerged as a leading photovoltaic technology due to their high efficiency and low cost. Even though they have developed rapidly since their inception, with efficiencies of over 26%, inverted PSCs face challenges such as nonradiative recombination and ion migration. Surface treatment, especially the utilization of organic compounds, has improved efficiency and stability by optimizing the perovskite-charge transport layer interface. Herein, we report a facile and effective strategy by introducing 2,2'-bipyridyl to modify the surface of perovskite, achieving a power conversion efficiency of 24.43% with increasing open-circuit voltage and fill factor and good repeatability on multiple devices. We reveal that the 2,2'-bipyridyl molecule can chelate lead ions on the surface of perovskite, effectively suppressing nonradiative recombination. Furthermore, this modification can induce surficial n-doping to refine the energy level alignment, thereby minimizing charge transport losses. Additionally, the device maintained over 92% of the initial efficiency after 1000 h of operation at the maximum power point under continuous illumination. This surface chelation and defect passivation strategy employing 2,2'-bipyridyl offers a promising avenue for exploring the details of potential long-term degradation mechanisms and the development of commercially viable high-performance p-i-n PSCs.

Efficient All‐Polymer Solar Cells Enabled by a Novel Medium Bandgap Guest Acceptor

Comprehensive SummaryNear‐infrared (NIR)‐absorbing polymerized small molecule acceptors (PSMAs) based on a Y‐series backbone (such as PY‐IT) have been widely developed to fabricate efficient all‐polymer solar cells (all‐PSCs). However, medium‐bandgap PSMAs are often overlooked, while they as the third component can be expected to boost power conversion efficiencies (PCEs) of all‐PSCs, mainly due to their up‐shifted lowest unoccupied molecular orbital (LUMO) energy level, complimentary absorption, and diverse intermolecular interaction compared to the NIR‐absorbing host acceptor. Herein, an IDIC‐series medium‐bandgap PSMA (P‐ITTC) is developed and introduced as the third component into D18/PY‐IT host, which can not only form complementary absorption and cascade energy level, but also finely optimize active layer morphology. Therefore, compared to the D18/PY‐IT based parental all‐PSCs, the ternary all‐PSCs based on D18/PY‐IT:P‐ITTC obtain an increased exciton dissociation, charge transport, carrier lifetime, as well as suppressed charge recombination and energy loss. As a result, the ternary all‐PSCs achieve a high PCE of 17.64% with a photovoltage of 0.96 V, both of which are among the top values in layer‐by‐layer typed all‐PSCs. This work provides a method for the design and selection of the medium‐bandgap third component to fabricate efficient all‐PSCs.