As advancements in artificial intelligence, the Internet of Things (IoT), and telecommunication technologies continue to accelerate, the demand for cheaper radiofrequency (RF) electronics increases. However, developing devices that meet the stringent manufacturing and performance criteria for RF applications remains a significant challenge. Here, we demonstrate organic polymeric RF Schottky diodes and rectifier circuits that can operate up to 18.5 GHz, making them the fastest organic devices reported to date. The diodes feature the molecularly n-doped polymer, namely N2200, deposited atop self-aligned coplanar asymmetric nanogap electrodes (sub-20-nm nanogaps). The coplanar architecture reduces parasitic capacitances, while the engineered electron-injecting contacts, in synergy with the n-doped polymer, help decrease the contact resistance and boost the device's overall performance. The polymer Schottky diodes exhibit a low turn-on voltage of ≈0.15 V, a high current rectification ratio exceeding 105, and an ultra-low capacitance of ≈2 pF. RF rectifier circuits featuring the polymer Schottky diodes yield a maximum output voltage (VPEAK) of 1.43 V and an extrinsic cut-off frequency of up to 18.5 GHz. The scalable manufacturing and unprecedented frequency response make these organic Schottky diodes a good candidate for applications in emerging RF electronics for wearables and the broader IoT device ecosystem.

Low-temperature, solution-processed carbon-based perovskite solar cells (c-PSCs) often suffer from surface defects and nonideal crystallization caused by rapid antisolvent quenching of MAPbI3. To this end, incorporating polymers as antisolvent additives offers a simple route to regulate crystallization and reduce interfacial defects. Here, four donor polymers-P3HT, PCE10, PM6, and PM7-are introduced during MAPbI3 deposition. Their distinct Highest Occupied Molecular Orbital (HOMO) energy levels enable us to probe how energetic alignment influences their interaction with MAPbI3 surfaces and their passivation capability. The additives are found to improve crystallinity, yielding larger grains and lower trap densities. In particular, PM7 provides the highest enhancements because its HOMO level lies closest to the MAPbI3 valence band, enabling more favorable interfacial passivation and more effective suppression of surface recombination. Consequently, PM7-treated films exhibit longer photocarrier lifetimes, lower ideality factors, reduced interfacial resistance, and smaller trap-filled limit voltages. Devices using PM7 reach a PCE of 14.6%, a 53.8% improvement over the control. Overall, this study demonstrates that the HOMO level of antisolvent additives is a decisive factor governing interfacial interactions and enhancing MAPbI3 passivation.

Oligomeric acceptors are increasingly recognized as promising n-type materials for organic photovoltaics (OPVs) due to their precise molecular structures, long-term stability, and high efficiency. However, inferior molecular packing and high energy losses have hindered their further use. Here, we overcome these challenges by developing an asymmetric small molecular acceptor (SMA), BTP-J17, and applying it as the second acceptor component in OPVs composed of PM6:DIBP3F-Se:BTP-J17 (refer to our recent work on dimeric acceptor DIBP3FSe). The BTP-J17 is very miscible with the DIBP3F-Se and appears to diffuse into the host donor-acceptor interface. The ensuing ternary cells exhibit enhanced exciton dissociation, improved carrier mobility, and more efficient charge extraction. Optimised OPVs based on PM6:DIBP3F-Se:BTP-J17 show enhanced open-circuit voltage (VOC) while maintaining the high short-circuit current (JSC) from the binary blends, boosting the power conversion efficiency (PCE) from 18.40 % to 19.60 %. By integrating MgF2 as an antireflection coating and ndoping the ternary BHJ with ethyl viologen (EV), we were able to further boost the PCE to 20.5 % (uncertified) and simultaneously extended the outdoor stability to seven weeks. Our findings highlight the crucial role of asymmetric SMA as an additional component for boosting the performance and stability of OPVs.

The development of low-power computing sectors requires compact, power-efficient and high-performance integrated circuits. Hybrid technology that combines n-type metal oxide thin-film transistors and p-type organic thin-film transistors offers a potential solution. However, increasing the transistor density of these systems through vertical stacking is challenging due to issues related to thermal budget and interface roughness. Here we report a six-stack hybrid complementary transistor technology that has 41 layers and uses n-type indium oxide (In2O3) and a p-type organic semiconductor (C16IDT-BT) as channel materials. We test 600 transistors and show that n-type oxide devices and p-type organic devices exhibit comparable field-effect mobilities and saturation currents. We also create 300 hybrid inverters by integrating the oxide and organic transistors; the circuits exhibit a gain of 94.84 V V−1 and a power consumption of 0.47 µW. We also fabricate NAND and NOR gates comprising transistors from four stacks. Thermal stability analysis shows that device characteristics begin to degrade above 50 °C, a known limitation of low-thermal-budget processes. Such performance is sufficient for many large-area electronics applications, but further thermal optimization will be necessary to extend operational robustness towards standard industrial conditions. A six-stack hybrid complementary transistor technology that uses n-type indium oxide and a p-type organic semiconductor as channel materials can be used to build inverters that exhibit a gain of 94.84 V V−1 and a power consumption of 0.47 µW.

We report a series of n-type conjugated polymers based on PNDI-TfBTT and PNDIV-TfBTT backbones constructed from electron-deficient naphthalene diimide (NDI) and fluorinated benzothiadiazole (fBT) units, with PNDIV-TfBTT incorporating a vinylene spacer. Quantitative postpolymerization modification (PPM) via nucleophilic substitution replaced the fBT fluorine with thioether side chains, optionally containing azide groups. Thioether substitution improved solubility, while subtly changing the ordering of polymer films. Azide incorporation enabled both thermal and photochemical crosslinking, yielding insoluble and immobile films that retained good electron transport; although UV crosslinking initially reduced mobility, subsequent thermal annealing largely restored crystallinity and performance. This work underscores the utility of precise backbone editing to fine-tune the electronic and morphological properties of n-type polymers, offering new avenues for the fabrication of stable, patterned active layers in advanced organic electronic devices.

The self-aligned gate (SAG) transistor architecture is attractive for electronic circuit applications due to its enabling attributes, including low parasitic capacitances and higher frequency operation. However, SAG transistors often rely on complex manufacturing, which limits their practical utilization. Herein, we overcome this bottleneck and demonstrate organic SAG transistors in which the self-aligned source/drain (S/D) electrodes are separated by the gate (G) terminal with sub-20 nm gaps. The SAG architecture eliminates parasitic overlaps while minimizing access resistance for the injected carriers. Moreover, precise work function engineering of the self-aligned Au S/D contacts is demonstrated using phosphonic acid (PA) self-assembled monolayers (SAMs) functionalized directly onto Au. Analysis of the Au surface corroborated by Density Functional Theory calculations and scanning tunneling microscopy reveal the unexpected formation of PA SAMs directly onto Au for the first time. Combining different organic semiconductors with appropriate SAMs enables the development of hole and electron-transporting SAG transistors with enhanced performance. Integrating the n- and p-channel transistors yields complementary logic circuitry with high gain and noise margins, showcasing the effectiveness of this approach. The work highlights the enormous potential of combining the SAG transistor platform with work function modifying PA SAMs to develop printed electronics with improved functionality.

We report three novel donor-acceptor (D-A) copolymers sharing a common fused donor unit (CDTT) but differing in the functionalization of the benzothiadiazole (BT) acceptor unit. Acceptors bearing two cyano groups (DCNBT) are compared to novel acceptors bearing one cyano and one fluorine group (FCNBT) or one nitro and one fluoro group (NO2FBT). The choice of the acceptor has a significant effect on the optoelectronic properties of the resulting polymers. In organic field-effect transistor (OFET) devices, PCDTT-DCNBT exhibited moderate performance with an electron mobility of 0.031 cm2 V-1 s-1, whereas PCDTT-FCNBT demonstrated significantly improved electron mobility (0.4 cm2 V-1 s-1). The improved performance is attributed to increased backbone linearity combined with a more coplanar backbone and high thin-film crystallinity. In comparison, the presence of the nitro group is shown to have a detrimental impact, with a blue-shifted absorption and a 0.2 eV increase in band gap compared to the cyanated polymers. Steric effects are shown to limit the nitro group's π-accepting capability and result in reduced device performance, with an electron mobility of 0.024 cm2 V-1 s-1. This study introduces a new BT building block and highlights that substituent tuning via cyano and fluorine groups is an effective approach for modulating polymer morphology and electron transport.

Self-assembled monolayers (SAMs) help improve the performance of organic electronic devices through interface passivation and enhanced carrier transport. Yet, there is limited information regarding the chemical structure of the SAMs upon functionalization and subsequent thermal treatment. Here, we studied the on-surface reaction of carbazole-derived SAMs on model gold electrodes, focusing on the chemical structure changes induced by thermal treatments. Furthermore, we correlate the microscopic changes with their impact on the electrode's work function. The carbazole-based SAMs first transform into organometallic complexes. At higher annealing temperatures, SAMs convert to oligomeric complexes. The observed chemical reactions significantly reduce the electrode work function and facilitate electron injection in n-type organic thin-film transistors. Our results highlight the on-surface synthesis of electronically active SAMs as an alternative approach for modifying the work function of electrodes for organic electronics.

Metal oxide thin-film transistors (TFTs) offer remarkable opportunities for applications in emerging transparent and flexible microelectronics. Unfortunately, their performance is hindered by limitations associated with parasitic effects, such as parasitic electrode overlap capacitances and high contact resistance, which can severely limit their dynamic behavior. Here, an innovative method is reported to fabricate coplanar self-aligned-gate (SAG) indium-gallium-zinc-oxide (IGZO) transistors with engineered source/drain contacts. The manufacturing process starts with the deposition and patterning of a gate electrode/dielectric stack and its functionalization with an organic self-assembled monolayer (SAM) as the surface energy modifier. A second gold (Au) electrode is subsequently deposited over the gate electrode stack. The overlapping region between the two electrodes is removed via self-delamination under mild sonication, forming perfectly aligned coplanar Au-Gate-Au electrodes. Device fabrication is completed with the spin coating of the IGZO precursor, followed by rapid photonic curing. Replacing the gold source/drain contact with bimetallic electrodes such as Au/In and Au/ITO enables a reduction in contact resistance and improves the transistor performance remarkably without increasing manufacturing complexity. The method is highly scalable, robust, and applicable to other semiconductor materials. Self-aligned gate transistors are developed with bilayer source/drain electrodes and a photonically cured indium-gallium-zinc-oxide as the semiconducting channel. The proposed transistor architecture minimizes the overlap capacitances and access resistance while enabling precise electrode work function engineering without increasing manufacturing complexity. The ensuing transistors exhibit high electron mobility, small subthreshold swing, and low contact resistance. image

Solution-processable poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is an important polymeric conductor used extensively in organic flexible, wearable, and stretchable optoelectronics. However, further enhancing its conductivity and long-term stability while maintaining its superb mechanical properties remains challenging. Here, a novel post-treatment approach to enhance the electrical properties and stability of sub-20-nm-thin PEDOT:PSS films processed from solution is introduced. The approach involves a sequential post-treatment with HNO3 and CsCl, resulting in a remarkable enhancement of the electrical conductivity of PEDOT:PSS films to over 5500 S cm-1, along with improved carrier mobility. The post-treated films exhibit remarkable air stability, retaining over 85% of their initial conductivity even after 270 days of storage. Various characterization techniques, including X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, Hall effect measurements, and grazing incidence wide angle X-ray scattering, coupled with density functional theory calculations, provide insights into the structural changes and interactions responsible for these improvements. To demonstrate the potential for practical applications, the ultrathin PEDOT:PSS films are connected to an inorganic light-emitting diode with a battery, showcasing their suitability as transparent electrodes. This work presents a promising approach for enhancing the electrical conductivity of PEDOT:PSS while offering a comprehensive understanding of the underlying mechanisms that can guide further advances.

Molecular doping is commonly utilized to tune the charge transport properties of organic semiconductors. However, applying this technique to electrically dope inorganic materials like metal oxide semiconductors is challenging due to the limited availability of molecules with suitable energy levels and processing characteristics. Herein, n-type doping of zinc oxide (ZnO) films is demonstrated using 1,3-dimethylimidazolium-2-carboxylate (CO2-DMI), a thermally activated organic n-type dopant. Adding CO2-DMI into the ZnO precursor solution and processing it atop a predeposited indium oxide (InOx) layer yield InOx/n-ZnO heterojunctions with increased electron field-effect mobility of 32.6 cm2 V-1 s-1 compared to 18.5 cm2 V-1 s-1 for the pristine InOx/ZnO bilayer. The improved electron transport originates from the ZnO's enhanced crystallinity, reduced hydroxyl concentrations, and fewer oxygen vacancy groups upon doping. Applying the optimally doped InOx/n-ZnO heterojunctions as the electron-transporting layers (ETLs) in organic photovoltaics (OPVs) yields cells with improved power conversion efficiency of 19.06%, up from 18.3% for devices with pristine ZnO, and 18.2% for devices featuring the undoped InOx/ZnO ETL. It is shown that the all-around improved OPV performance originates from synergistic effects associated with CO2-DMI doping of the thermally grown ZnO, highlighting its potential as an electronic dopant for ZnO and potentially other metal oxides.

The significant contact resistance at the metal-semiconductor interface is a well-documented issue for organic thin-film transistors (OTFTs) that hinders device and circuit performance. Here, this issue is tackled by developing three new thiol carbazole-based self-assembled monolayer (SAM) molecules, namely tBu-2SCz, 2SCz, and Br-2SCz, and utilizing them as carrier-selective injection interlayers. The SAMs alter the work function of gold electrodes by more than 1 eV, making them suitable for use in hole and electron-transporting OTFTs. Scanning tunneling microscopy analysis indicates that 2SCz and Br-2SCz form highly ordered molecular rows, resulting in work function values of 4.86 and 5.48 eV, respectively. The latter value is higher than gold electrodes modified by the commonly used pentafluorobenzenethiol (≈5.33 eV), making Br-2SCz promising for hole injection. Conversely, tBu-2SCz appears disordered with a lower work function of 4.52 eV, making it more suitable for electron injection. These intriguing properties are leveraged to demonstrate hole- and electron-transporting OTFTs with improved operating characteristics. All-organic complementary inverters are finally demonstrated by integrating p- and n-channel OTFTs, showcasing the potential of this simple yet powerful contact work function engineering approach. The present study highlights the versatility of thiol carbazole SAMs as carrier injecting interlayers for OTFTs and integrated circuits.

Recombination layers are crucial in achieving high power conversion efficiency (PCE) in tandem solar cells. Here, we report the development and optimization of recombination junctions for high PCE perovskite-organic tandem solar cells (PO-TSCs). We choose a wide bandgap perovskite (1.79 eV) for the front subcell and a narrow bandgap (1.36 eV) organic bulk heterojunction (BHJ) for the rear subcell. The optimal thicknesses of the perovskite and organic layers were determined to be 260 and 100 nm, respectively, based on the analysis of Transfer-Matrix optical simulations. Our results demonstrate that the optimal recombination layer consists of an ultrathin layer of indium zinc oxide IZO (similar to 2 nm) deposited on MoOx/2PACz, which delivers a PCE of 23.6 %. This high PCE is attributed to the high transparency of the recombination layer in the NIR spectra region and the low sheet resistance of IZO. Furthermore, we provide a theoretical analysis of the potential efficiency of PO-TSCs as a function of front and rear subcells and predict a maximum theoretical PCE value of more than 36 %. Our work highlights the importance of selecting the proper recombination layer design for achieving high-performance PO-TSCs.

Poly(3,4-ethylenedioxythiophene): polystyrenesulfonate (PEDOT:PSS) is widely used as a hole transport layer (HTL) in emerging solar cells. It is highly compatible with roll-to-roll deposition, paving the way for utilization in flexible solar cells. However, its mismatched energy levels and acidity limit its performance and stability. This study focuses on the modification of PEDOT:PSS HTL with vanadium oxide $\left(V_{2} O_{5}\right)$ additive to improve the performance of inverted $p-i-n$ perovskite solar cells (PSCs). The $V_{2} O_{5}$ was prepared from an aqueous ammonia solution and directly added to the PEDOT:PSS solution. Devices employing $V_{2} O_{5}$:PEDOT:PSS (VPP) HTL with a concentration of $8 mg/ml(w/v)$ exhibit remarkable performance improvement compared to devices using pristine PEDOT:PSS, with the power conversion efficiency (PCE) rising from 7.7 % to 9.0 %. Furthermore, key parameters, including open-circuit voltage ($V_{o c}$), short-circuit current ($J_{S C}$), and fill factor (FF), all showed improvements, recorded at 0.95 V, 16.0 $mAcm^{-2}$, and 58.6 %, respectively. Additionally, the responsiveness of light-to-current conversion exhibits a notable increase, highlighting the potential $V_{2}O_{5}$ additive, prepared using a simple method, to achieve superior performance in inverted p $i-n$ PSC. The finding also opens avenues for further exploration of other metal oxide additives, addressing specific challenges in HTL deposition.

Molecular doping has become a valuable technique for enhancing the efficiency of high-performance organic photovoltaic systems (OPVs). However, the number of known dopant molecules, especially n-type ones, that enhance the PCE of OPVs remains limited. In this study, two n-type dopants, ethyl viologen (EV) and methyl viologen (MV), are synthesized and incorporated into ternary PM6:BTP-eC9:PC71BM bulk heterojunction (BHJ) OPVs. Both dopants are found to enhance the OPV performance, yielding maximum PCE values of 19.03% and 18.61%, respectively. We show that EV and MV function as n-type dopants and microstructure modifiers, enhancing p-p stacking while increasing the absorption coefficient of the BHJs. Moreover, the n-doping balances the carrier mobility while increasing the carrier lifetime and reducing bimolecular recombination. Our results demonstrate the potential of EV and MV to improve the performance of highly efficient OPVs to levels beyond those achievable by the pristine BHJ.

Semiconducting colloidal quantum dots (CQDs) represent an emerging class of thermoelectric materials for use in a wide range of future applications. CQDs combine solution processability at low temperatures with the potential for upscalable manufacturing via printing techniques. Moreover, due to their low dimensionality, CQDs exhibit quantum confinement and a high density of grain boundaries, which can be independently exploited to tune the Seebeck coefficient and thermal conductivity, respectively. This unique combination of attractive attributes makes CQDs very promising for application in emerging thermoelectric generator (TEG) technologies operating near room temperature. Herein, recent progress in CQDs for application in emerging thin-film thermoelectrics is reviewed. First, the fundamental concepts of thermoelectricity in nanostructured materials are outlined, followed by an overview of the popular synthetic methods used to produce CQDs with controllable sizes and shapes. Recent strides in CQD-based thermoelectrics are then discussed with emphasis on their application in thin-film TEGs. Finally, the current challenges and future perspectives for further enhancing the performance of CQD-based thermoelectric materials for future applications are discussed.

Formamidinium lead triiodide (FAPbI3) is the leading candidate for single-junction metal-halide perovskite photovoltaics, despite the metastability of this phase. To enhance its ambient-phase stability and produce world-record photovoltaic efficiencies, methylenediammonium dichloride (MDACl2) has been used as an additive in FAPbI3. MDA2+ has been reported as incorporated into the perovskite lattice alongside Cl-. However, the precise function and role of MDA2+ remain uncertain. Here, we grow FAPbI3 single crystals from a solution containing MDACl2 (FAPbI3-M). We demonstrate that FAPbI3-M crystals are stable against transformation to the photoinactive δ-phase for more than one year under ambient conditions. Critically, we reveal that MDA2+ is not the direct cause of the enhanced material stability. Instead, MDA2+ degrades rapidly to produce ammonium and methaniminium, which subsequently oligomerizes to yield hexamethylenetetramine (HMTA). FAPbI3 crystals grown from a solution containing HMTA (FAPbI3-H) replicate the enhanced α-phase stability of FAPbI3-M. However, we further determine that HMTA is unstable in the perovskite precursor solution, where reaction with FA+ is possible, leading instead to the formation of tetrahydrotriazinium (THTZ-H+). By a combination of liquid- and solid-state NMR techniques, we show that THTZ-H+ is selectively incorporated into the bulk of both FAPbI3-M and FAPbI3-H at ∼0.5 mol % and infer that this addition is responsible for the improved α-phase stability.

As a new family in carbon nanomaterials, carbon dots (CDs) are potential candidates for solar water evaporator, owing to their cost-effectiveness, non-toxicity, high solubility, and tunable optical properties. Despite such potentials, however, CDs mainly absorb solar spectrum in the ultraviolet region while their absorption in the visible region is limited, the characteristics that hinder their functionality in generating steam from solar energy. Herein, the optical and photothermal properties of CDs, derived from urea and citric acid, can be modulated by controlling their surface stoichiometry through varying the molar ratio of the precursors. Our approach is simple, fast, and highly scalable by utilizing a microwave irradiation technique. We found that increasing the nitrogen content results in broadening of the absorption spectra into the visible region due to more functional groups introduced on the CD surface that reduce the band gap, as confirmed both by X-ray photoelectron spectroscopy and theoretical calculation. Employing the CDs as photothermal materials in the volumetric solar evaporator, we demonstrate a remarkable evaporation efficiency of up to 70% along with a volumetric evaporation rate of 1.11 kg m-2 h-1 under 1 sun illumination, superior to direct bulk water heating. Furthermore, the CDs show excellent durability and stability, as demonstrated by their stable evaporation rate for 10 days, with no significant decrease in the optical and photothermal properties. This finding provides a pathway to design and functionalize CDs with controllable optical and photothermal properties for an efficient solar evaporation system.

Molecular doping is a powerful and increasingly popular approach toward enhancing electronic properties of organic semiconductors (OSCs) past their intrinsic limits. The development of n‐type dopants has been hampered, however, by their poor stability and high air‐reactivity, a consequence of their generally electron rich nature. Here, the use of air‐stable carboxylated dopant precursors is reported to overcome this challenge. Active dopants are readily generated in solution by thermal decarboxylation and applied in n‐type organic field‐effect transistors (OFETs). Both 1,3‐dimethylimidazolium‐2‐carboxylate (CO 2 ‐DMI) and novel dopant 1,3‐dimethylbenzimidazolium‐2‐carboxylate (CO 2 ‐DMBI) are applied to n‐type OFETs employing well‐known organic semiconductors (OSCs) P(NDI2OD‐T2), PCBM, and O‐IDTBR. Successful improvement of performance in all devices demonstrates the versatility of the dopants across a variety of OSCs. Experimental and computational studies indicate that electron transfer from the dopant to the host OSC is preceded by decarboxylation of the precursor, followed by dimerization to form the active dopant species. Transistor studies highlight CO 2 ‐DMBI as the most effective dopant, improving electron mobility by up to one order of magnitude, while CO 2 ‐DMI holds the advantage of commercial availability.