Semiconducting Polymer Research Articles

Augmenting Immunogenic Cell Death and Alleviating Myeloid-Derived Suppressor Cells by Sono-Activatable Semiconducting Polymer Nanopartners for Immunotherapy.

Inducing immunogenic cell death (ICD) by sonodynamic therapy (SDT) is promising for cancer immunotherapy, which however is inefficient due to oxygen depletion that compromises SDT effect and mediates recruitment of immunosuppressive myeloid-derived suppressor cells (MDSCs). The fabrication of sono-activatable semiconducting polymer nanopartners (SPNTi ) to simultaneously augment ICD and alleviate MDSCs for immunotherapy is reported. A sonodynamic semiconducting polymer, hydrophobic hypoxia-responsive tirapazamine (TPZ)-conjugate, and MDSC-targeting drug (ibrutinib) are encapsulated inside such SPNTi with surface shell of a singlet oxygen (1 O2 )-cleavable amphiphilic polymer. TPZ and ibrutinib serve as drug partners to enlarge immunotherapeutic effect. Upon sono-activation, SPNTi generate 1 O2 to break 1 O2 -cleavable polymers for in-situ liberations of TPZ-conjugate and ibrutinib in tumor sites, and oxygen is consumed to create severer hypoxic tumor microenvironment, in which, TPZ-conjugate is activated for augmenting ICD action, while ibrutinib alleviates MDSCs for promoting antitumor immunological effect. In a bilateral tumor mouse model, SPNTi -mediated sono-activatable immunotherapy results in growth restraints of primary and distant tumors and noteworthy precaution of tumor metastases. This study thus provides a sono-activatable immunotherapeutic strategy with high precision and safety for cancer via overcoming post-treatment hypoxia and targeting MDSCs. This article is protected by copyright. All rights reserved.

Cross‐Plane Thermal Transport in Acceptor‐Doped Thiophene‐Based Polymer Thin Films Investigated by the 3‐Omega Method

Thermal transport properties in acceptor‐doped thiophene‐based polymer films such as poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) and poly[2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene] (PBTTT) are investigated using the cross‐plane 3‐omega method. A bilayer structure consisting of polymer semiconductors sequentially doped with 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4TCNQ) and poly(methylmethacrylate) (PMMA) on a Si substrate is originally prepared by spin coating and employed to prevent leakage current from a heater wire during the 3‐omega measurements. Nondoped PBTTT thin film reveals an intrinsic cross‐plane thermal conductivity of 0.49 W m−1 K−1, which is higher than that for nondoped P3HT film (0.20 W m−1 K−1). X‐ray diffraction (XRD) analysis suggests that higher crystallinity of PBTTT films may result in higher thermal conductivity. The intrinsic thermal conductivity of P3HT and the interfacial thermal resistance between PMMA and P3HT are slightly increased at a low doping concentration (0.01 mg mL−1) and decreased at a higher doping concentration of 0.1 mg mL−1, whereas F4TCNQ doping reduces these values monotonously in the case of PBTTT layers. Furthermore, excess doping occurs only for P3HT and increments both intrinsic thermal conductivity and thermal resistance at PMMA/P3HT interface. The observed trend in the cross‐plane thermal transport caused by the sequential doping can be attributed to the differences between P3HT and PBTTT in their crystallinity and effective doping levels.

Synthesis and Optoelectronic Applications of dπ–pπ Conjugated Polymers with a Di‐metallaaromatic Acceptor

AbstractThe development of conjugated polymers especially n‐type polymer semiconductors is powered by the design and synthesis of electron‐deficient building blocks. Herein, a strong acceptor building block with di‐metallaaromatic structure was designed and synthesized by connecting two electron‐deficient metallaaromatic units through a π‐conjugated bridge. Then, a double‐monomer polymerization methodology was developed for inserting it into conjugated polymer scaffolds to yield metallopolymers. The isolated well‐defined model oligomers indicated polymer structures. Kinetic studies based on nuclear magnetic resonance and ultraviolet–visible spectroscopies shed light on the polymerization process. Interestingly, the resulted metallopolymers with dπ–pπ conjugations are very promising electron transport layer materials which can boost photovoltaic performance of an organic solar cell, with power conversion efficiency up to 18.28 % based on the PM6 : EH‐HD‐4F non‐fullerene system. This work not only provides a facile route to construct metallaaromatic conjugated polymers with various functional groups, but also discovers their potential applications for the first time.

Synthesis and Optoelectronic Applications of dπ-pπ Conjugated Polymers with a Di-metallaaromatic Acceptor.

The development of conjugated polymers especially n-type polymer semiconductors is powered by the design and synthesis of electron-deficient building blocks. Herein, a strong acceptor building block with di-metallaaromatic structure was designed and synthesized by connecting two electron-deficient metallaaromatic units through a π-conjugated bridge. Then, a double-monomer polymerization methodology was developed for inserting it into conjugated polymer scaffolds to yield metallopolymers. The isolated well-defined model oligomers indicated polymer structures. Kinetic studies based on NMR and UV/Vis spectroscopies shed light on the polymerization process. Interestingly, the resulted metallopolymers with dπ-pπ conjugations are very promising electron transport layer materials which can boost photovoltaic performance of an organic solar cell, with power conversion efficiency up to 18.28% based on the PM6:EH-HD-4F non-fullerene system. This work not only provides a facile route to construct metallaaromatic conjugated polymers with various functional groups, but also discovers their potential applications for the first time.

Efficient photosynthesis of hydrogen peroxide by triazole-modified covalent triazine framework nanosheets

Two-dimensional (2D) polymeric semiconductors, especially covalent triazine framework (CTF) nanosheets with aromatic triazine linkages are emerging as attractive metal-free photocatalysts owing to their predictable structures, good semiconducting properties, and high stability. However, the quantum size effect and ineffective electron screening of 2D CTF nanosheets cause an enlargement of electronic band gap and high excited electron-hole binding energies, which lead to low-level enhancements in photocatalytic performance. Herein, we present a novel triazole groups functionalized CTF nanosheet (CTF-LTZ) synthesized by facile combination of ionothermal polymerization and freeze-drying strategy from the unique letrozole precursor. The incorporation of the high-nitrogen-containing triazole group effectively modulates the optical and electronic properties, resulting in narrowed bandgap from 2.92 eV for unfunctionalized CTF to 2.22 eV for CTF-LTZ and dramatically improved charge separation, as well as highly-active sites for O2 adsorption. As a result, CTF-LTZ photocatalyst exhibits excellent performance and superior stability in H2O2 photosynthesis, with a high H2O2 production rate of 4068 μmol h−1 g−1 and a remarkable apparent quantum efficiency of 4.5 % at 400 nm. This work provides a simple and effective approach for rational design highly-efficient polymeric photocatalysts for H2O2 production.

Side-Chain Molecular Engineering of Triazole-Based Donor-Acceptor Polymeric Photocatalysts with Strong Electron Push-Pull Interactions.

A new series of donor-acceptor (D-A)-type semiconductive polymers were generated by the integration of electron-deficient alkyl chain anchored triazole (TA) moieties and electron-rich pyrene units into the polymer skeleton. The polymer series demonstrated satisfactory light-harvesting ability and suitable band gaps. In the series, polymer P-TAME benefits from a minimized exciton binding energy, strongest D-A interaction, and favorable hydrophilicity, affording an outstanding photocatalytic H2 evolution rate of ca. 100 μmol h-1 (10 mg polymer, AQY420 nm =8.9 %) and H2 O2 production rate of ca. 190 μmol h-1 (20 mg polymer) under visible-light irradiation, which is superior to most currently reported polymers. All polymers in the series can mediate water oxidation reactions to evolve O2 . Thus, these TA-based polymers open up a new avenue toward tailor-made efficient photocatalysts with broad photocatalytic activities.

Side‐Chain Molecular Engineering of Triazole‐Based Donor‐Acceptor Polymeric Photocatalysts with Strong Electron Push‐Pull Interactions

AbstractA new series of donor‐acceptor (D‐A)‐type semiconductive polymers were generated by the integration of electron‐deficient alkyl chain anchored triazole (TA) moieties and electron‐rich pyrene units into the polymer skeleton. The polymer series demonstrated satisfactory light‐harvesting ability and suitable band gaps. In the series, polymer P‐TAME benefits from a minimized exciton binding energy, strongest D‐A interaction, and favorable hydrophilicity, affording an outstanding photocatalytic H2 evolution rate of ca. 100 μmol h−1 (10 mg polymer, AQY420 nm=8.9 %) and H2O2 production rate of ca. 190 μmol h−1 (20 mg polymer) under visible‐light irradiation, which is superior to most currently reported polymers. All polymers in the series can mediate water oxidation reactions to evolve O2. Thus, these TA‐based polymers open up a new avenue toward tailor‐made efficient photocatalysts with broad photocatalytic activities.

Stretchable and Self‐Healable Semiconductive Composites Based on Hydrogen Bonding Cross‐linked Elastomeric Matrix

AbstractSemiconductors with both high stretchability and self‐healing capability are highly desirable for various wearable devices. Much progress has been achieved in designing highly stretchable semiconductive polymers or composites. The demonstration of self‐healable semiconductive composite is still rare. Here, an extremely soft, highly stretchable, and self‐healable hydrogen bonding cross‐linked elastomer, amide functionalized‐polyisobutylene (PIB‐amide) is developed, to enable a self‐healable semiconductive composite through compounding with a high‐performance conjugated diketopyrrolopyrrole (DPP‐T) polymer. The composite, consisting of 20% DPP‐T and 80% PIB‐amide, shows record high crack‐onset strain (COS ≈1500%), extremely low elastic modulus (E≈1.6 MPa), and unique ability to spontaneously self‐heal atroom temperature within 5 min. Unlike previous works, these unique composite materials also show strain‐independent charge mobility. An in‐depth morphological study based on multi‐model techniques indicate that all composites show blending ratio‐ and stretching‐independent fibril‐like aggregation due to the strong hydrogen bond in elastomer to enable the unique stable charge mobility. This study provides a new direction to develop highly healable and electronically stable semiconductive composite and will enable new applications of stretchable electronics.

Environmentally stable and stretchable polymer electronics enabled by surface-tethered nanostructured molecular-level protection.

Stretchable polymer semiconductors (PSCs) are essential for soft stretchable electronics. However, their environmental stability remains a longstanding concern. Here we report a surface-tethered stretchable molecular protecting layer to realize stretchable polymer electronics that are stable in direct contact with physiological fluids, containing water, ions and biofluids. This is achieved through the covalent functionalization of fluoroalkyl chains onto a stretchable PSC film surface to form densely packed nanostructures. The nanostructured fluorinated molecular protection layer (FMPL) improves the PSC operational stability over an extended period of 82 days and maintains its protection under mechanical deformation. We attribute the ability of FMPL to block water absorption and diffusion to its hydrophobicity and high fluorination surface density. The protection effect of the FMPL (~6 nm thickness) outperforms various micrometre-thick stretchable polymer encapsulants, leading to a stable PSC charge carrier mobility of ~1 cm2 V-1 s-1 in harsh environments such as in 85-90%-humidity air for 56 days or in water or artificial sweat for 42 days (as a benchmark, the unprotected PSC mobility degraded to 10-6 cm2 V-1 s-1 in the same period). The FMPL also improved the PSC stability against photo-oxidative degradation in air. Overall, we believe that our surface tethering of the nanostructured FMPL is a promising approach to achieve highly environmentally stable and stretchable polymer electronics.

Shockproof Deformable Infrared Radiation Sensors Based on a Polymeric Rubber and Organic Semiconductor H2Pc-CNT Composite.

Polymeric rubber and organic semiconductor H2Pc-CNT-composite-based surface- and sandwich-type shockproof deformable infrared radiation (IR) sensors were fabricated using a rubbing-in technique. CNT and CNT-H2Pc (30:70 wt.%) composite layers were deposited on a polymeric rubber substrate as electrodes and active layers, respectively. Under the effect of IR irradiation (0 to 3700 W/m2), the resistance and the impedance of the surface-type sensors decreased up to 1.49 and 1.36 times, respectively. In the same conditions, the resistance and the impedance of the sandwich-type sensors decreased up to 1.46 and 1.35 times, respectively. The temperature coefficients of resistance (TCR) of the surface- and sandwich-type sensors are 1.2 and 1.1, respectively. The novel ratio of the H2Pc-CNT composite ingredients and comparably high value of the TCR make the devices attractive for bolometric applications meant to measure the intensity of infrared radiation. Moreover, given their easy fabrication and low-cost materials, the fabricated devices have great potential for commercialization.

P‐type Semiconducting Polymers as Photocathodes: A Comparative Study for Optobioelectronics

AbstractRecent studies have shown that p‐type polymeric semiconductors enable a new type of wireless, optically triggered interface with cells and tissues. Poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) has already been used to create such optobioelectronic interfaces, producing reactive oxygen species and hydrogen peroxide that act as messengers in biological systems to impact cell signaling and proliferation. However, the use of P3HT in biomedical in‐vivo applications is limited as its optical absorption does not match the tissue transparency window. This paper compares the performance of P3HT with two low band‐gap polymers commonly employed in high‐performance organic solar cells, namely Poly[[4,8‐bis[5‐(2‐ethylhexyl)‐2‐thienyl]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl]‐2,5‐thiophenediyl[5,7‐bis(2‐ethylhexyl)‐4,8‐dioxo‐4H,8H‐benzo[1,2‐c:4,5‐c′]dithiophene‐1,3‐diyl]] (PBDB‐T) and Poly({4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b′]dithiophene‐2,6‐diyl}{3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b] thiophenediyl}) (PTB7). Their photogeneration capabilities are quantified in physiological‐like conditions through photocurrent analysis and a hydrogen peroxide assay, finding a superior photocurrent generation and a better H2O2 photogeneration yield in PTB7 as compared to the other two polymers. Spectroscopic and structural investigations are used to compare such differences by comparing their energy levels at the electrochemical interface and their morphologies. Finally, biocompatibility is tested both in dark and illuminated conditions and effective in‐vitro intracellular ROS production is demonstrated. These findings provide insight into the physico‐chemical properties crucial for the development of novel, less invasive, optically operated bioelectronic interfaces.

High-performance flexible organic field effect transistors with print-based nanowires

Polymer nanowire (NW) organic field-effect transistors (OFETs) integrated on highly aligned large-area flexible substrates are candidate structures for the development of high-performance flexible electronics. This work presents a universal technique, coaxial focused electrohydrodynamic jet (CFEJ) printing technology, to fabricate highly aligned 90-nm-diameter polymer arrays. This method allows for the preparation of uniformly shaped and precisely positioned nanowires directly on flexible substrates without transfer, thus ensuring their electrical properties. Using indacenodithiophene-co-benzothiadiazole (IDT-BT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8-BT) as example materials, 5 cm2 arrays were prepared with only minute size variations, which is extremely difficult to do using previously reported methods. According to 2D-GIXRD analysis, the molecules inside the nanowires mainly adopted face-on π-stacking crystallite arrangements. This is quite different from the mixed arrangement of thin films. Nanowire-based OFETs exhibited a high average hole mobility of 1.1 cm2 V−1 s−1 and good device uniformity, indicating the applicability of CFEJ printing as a potential batch manufacturing and integration process for high-performance, scalable polymer nanowire-based OFET circuits. This technique can be used to fabricate various polymer arrays, enabling the use of organic polymer semiconductors in large-area, high-performance electronic devices and providing a new path for the fabrication of flexible displays and wearable electronics in the future.

Spectral Signatures of a Negative Polaron in a Doped Polymer Semiconductor: Energy Levels and Hubbard U Interactions.

The modern picture of negative charge carriers on conjugated polymers invokes the formation of a singly occupied (spin-up/spin-down) level within the polymer gap and a corresponding unoccupied level above the polymer conduction band edge. The energy splitting between these sublevels is related to on-site Coulomb interactions between electrons, commonly termed Hubbard U. However, spectral evidence for both sublevels and experimental access to the U value is still missing. Here, we provide evidence by n-doping the polymer P(NDI2OD-T2) with [RhCp*Cp]2, [N-DMBI]2, and cesium. Changes in the electronic structure after doping are studied with ultraviolet photoelectron and low-energy inverse photoemission spectroscopies (UPS, LEIPES). UPS data show an additional density of states (DOS) in the former empty polymer gap while LEIPES data show an additional DOS above the conduction band edge. These DOS are assigned to the singly occupied and unoccupied sublevels, allowing determination of a U value of ∼1 eV.

Quinoxalineimide-Based Semiconducting Polymer Nanoparticles as an Effective Phototheranostic for the Second Near-Infrared Fluorescence Imaging and Photothermal Therapy.

Multifunctional theranostics play a critical role in improving the efficacy of photothermal therapy and tumor fluorescence imaging; however, they require the integration of complex components into a single theranostic system, and their response in the second near-infrared (NIR-II) region is constrained by wavelengths of a photosensitizer. To address this issue, we herein developed a novel multifunctional thiazole-fused quinoxalineimide semiconducting polymer (named PQIA-BDTT), which exhibits NIR-II fluorescence and photothermal properties. PQIA-BDTT nanoparticles achieved an impressively high photothermal conversion efficiency (72.6%) in laser (1064 nm)-induced photothermal therapy at a safe maximum permissible exposure, demonstrating their capability as an effective photothermal agent. Moreover, PQIA-BDTT nanoparticles can be used as a reference for NIR-II fluorescence imaging under a low laser fluence. The tumor size and location in 4T1 mice intravenously injected with the PQIA-BDTT nanoparticles could be precisely identified through NIR-II fluorescence imaging, which also exhibited remarkable photothermal antitumor efficacy by in vitro and in vivo therapy. Overall, this study demonstrates that introducing a thiazole-fused quinoxalineimide acceptor unit into a donor-acceptor conjugated polymer is an effective strategy for the synthesis of novel multifunctional theranostic systems, which provides a novel platform for designing theranostic agents for biomedical applications.

Enhanced sub-1 eV detection in organic photodetectors through tuning polymer energetics and microstructure.

One of the key challenges facing organic photodiodes (OPDs) is increasing the detection into the infrared region. Organic semiconductor polymers provide a platform for tuning the bandgap and optoelectronic response to go beyond the traditional 1000-nanometer benchmark. In this work, we present a near-infrared (NIR) polymer with absorption up to 1500 nanometers. The polymer-based OPD delivers a high specific detectivity D* of 1.03 × 1010 Jones (-2 volts) at 1200 nanometers and a dark current Jd of just 2.3 × 10-6 ampere per square centimeter at -2 volts.We demonstrate a strong improvement of all OPD metrics in the NIR region compared to previously reported NIR OPD due to the enhanced crystallinity and optimized energy alignment, which leads to reduced charge recombination. The high D* value in the 1100-to-1300-nanometer region is particularly promising for biosensing applications. We demonstrate the OPD as a pulse oximeter under NIR illumination, delivering heart rate and blood oxygen saturation readings in real time without signal amplification.

Channel length effect of P3HT:ZnO hybrid blend layer on electrical characteristics of thin-film transistors

In this present work, p-type bottom gate-bottom contact OTFTs based on semiconductor polymer poly(3-hexylthiophene) (P3HT) incorporating zinc oxide nanoparticles (ZnO) (OTFTs-P3HT:ZnO hybrid blend) with various channel lengths (L=2.5 µm, 5 µm, 10 µm and 20 µm) and constant channel width (W=10 mm) were elaborated using solution-processed P3HT:ZnO thin films, as an active layer, deposited on a Si/SiO2 substrate, without any surface treatment, by spin coating technique, and then were characterized. ZnO nanoparticles are utilized as acceptors and electron extraction materials. The effect of the channel length variation on the electrical parameters of these transistors at room atmosphere in saturation regime, has been investigated in order to better understand the dependency between the electrical performance and the channel length variation effect. As p-channel transistors, the fabricated devices exhibit a considerable variation in electrical parameters such as amount of hysteresis (△Vhyst), threshold voltage (Vth), density of trapped charges (Ntrap), sub-threshold slope (SS), density of the interface trap (Dit), field-effect saturation mobility (µsat) and current ratio (Ion/Ioff) with the increase of the channel length. In this study, we report a significant improvement in the efficiency of our devices in terms of good output characteristics and good electrical parameters such as low threshold voltage, low Ioff current, reduction of trap density and better field-effect saturation mobility when the channel length increases. These particularly promising results offer the possibility of using these organic thin-film transistors in several application domains such as low-cost sensing and non-volatile memory devices.

Activatable Semiconducting Polymer Pro-nanomodulators for Deep-Tissue Sono-immunotherapy of Orthotopic Pancreatic Cancer.

Immunotherapy has provided a promising modality for cancer treatment, while it often has the issues of limited response rates and potential off-target side effects in clinical practice. We herein report the construction of semiconducting polymer pro-nanomodulators (SPpMs) with ultrasound (US)-mediated activatable pharmacological actions for deep-tissue sono-immunotherapy of orthotopic pancreatic cancer. Such SPpMs consist of a sonodynamic semiconducting polymer backbone grafted with poly(ethylene glycol) chains linked with two immunomodulators (a programmed death-ligand 1 blocker and an indoleamine 2,3-dioxygenase inhibitor) via a singlet oxygen (1 O2 )-cleavable segment. In view of the excellent sonodynamic property of the semiconducting polymer core, SPpMs enable effective generation of 1 O2 under US treatment, even in a deep-tissue depth up to 12 cm. The generated 1 O2 not only ablates tumors via a sonodynamic effect and induces immunogenic cell death, but also destroys the 1 O2 -cleavable segments to allow in situ release of immunomodulators in tumors. This synergetic action results in boosted antitumor immune response via reversing two tumor immunosuppressive pathways. As such, SPpMs mediate deep-tissue sono-immunotherapy to completely eradicate orthotopic pancreatic cancer and effectively prevent tumor metastasis. Moreover, such an immune activation reduces the possibility of immune-related adverse events. This study thus provides a smart activatable nanoplatform for precise immunotherapy of deep-seated tumors.

Activatable Semiconducting Polymer Pro‐nanomodulators for Deep‐Tissue Sono‐immunotherapy of Orthotopic Pancreatic Cancer

AbstractImmunotherapy has provided a promising modality for cancer treatment, while it often has the issues of limited response rates and potential off‐target side effects in clinical practice. We herein report the construction of semiconducting polymer pro‐nanomodulators (SPpMs) with ultrasound (US)‐mediated activatable pharmacological actions for deep‐tissue sono‐immunotherapy of orthotopic pancreatic cancer. Such SPpMs consist of a sonodynamic semiconducting polymer backbone grafted with poly(ethylene glycol) chains linked with two immunomodulators (a programmed death‐ligand 1 blocker and an indoleamine 2,3‐dioxygenase inhibitor) via a singlet oxygen (1O2)‐cleavable segment. In view of the excellent sonodynamic property of the semiconducting polymer core, SPpMs enable effective generation of 1O2 under US treatment, even in a deep‐tissue depth up to 12 cm. The generated 1O2 not only ablates tumors via a sonodynamic effect and induces immunogenic cell death, but also destroys the 1O2‐cleavable segments to allow in situ release of immunomodulators in tumors. This synergetic action results in boosted antitumor immune response via reversing two tumor immunosuppressive pathways. As such, SPpMs mediate deep‐tissue sono‐immunotherapy to completely eradicate orthotopic pancreatic cancer and effectively prevent tumor metastasis. Moreover, such an immune activation reduces the possibility of immune‐related adverse events. This study thus provides a smart activatable nanoplatform for precise immunotherapy of deep‐seated tumors.

Oxidative-Reductive Near-Infrared Electrochromic Switching Enabled by Porous Vertically Stacked Multilayer Devices.

Here, we demonstrate for the first time the ability of a porous π-conjugated semiconducting polymer film to enable facile electrolyte penetration through vertically stacked redox-active polymer layers, thereby enabling electrochromic switching between p-type and/or n-type polymers. The polymers P1 and P2, with structures diketopyrrolopyrrole (DPP)-πbridge-3,4,-ethylenedioxythiophene (EDOT)-πbridge [πbridge = 2,5-thienyl for P1 and πbridge = 2,5-thiazolyl for P2] are selected as the p-type polymers and N2200 (a known naphthalenediimide-dithiophene semiconductor) as the n-type polymer. Single-layer porous and dense (control) polymer films are fabricated and extensively characterized using optical microscopy, atomic force microscopy, scanning electron microscopy, and grazing incidence wide-angle X-ray scattering. The semiconducting films are then incorporated into single and multilayer electrochromic devices (ECDs). It is found that when a p-type (P2) porous top layer is used in a multilayer ECD, it enables electrolyte penetration to the bottom layer, enabling oxidative electrochromic switching of the P1 bottom layer at low potentials (+0.4 V versus +1.2 V with dense P2). Importantly, when using a porous P1 as the top layer with an n-type N2200 bottom layer, dynamic oxidative-reductive electrochromic switching is also realized. These results offer a proof of concept for development of new types of multilayer electrochromic devices where precise control of the semiconductor film morphology and polymer electronic structure is essential.

Proposal and Numerical Analysis of Organic/Sb2Se3 All-Thin-Film Tandem Solar Cell.

The low bandgap antimony selenide (Sb2Se3) and wide bandgap organic solar cell (OSC) can be considered suitable bottom and top subcells for use in tandem solar cells. Some properties of these complementary candidates are their non-toxicity and cost-affordability. In this current simulation study, a two-terminal organic/Sb2Se3 thin-film tandem is proposed and designed through TCAD device simulations. To validate the device simulator platform, two solar cells were selected for tandem design, and their experimental data were chosen for calibrating the models and parameters utilized in the simulations. The initial OSC has an active blend layer, whose optical bandgap is 1.72 eV, while the initial Sb2Se3 cell has a bandgap energy of 1.23 eV. The structures of the initial standalone top and bottom cells are ITO/PEDOT:PSS/DR3TSBDT:PC71BM/PFN/Al, and FTO/CdS/Sb2Se3/Spiro-OMeTAD/Au, while the recorded efficiencies of these individual cells are about 9.45% and 7.89%, respectively. The selected OSC employs polymer-based carrier transport layers, specifically PEDOT:PSS, an inherently conductive polymer, as an HTL, and PFN, a semiconducting polymer, as an ETL. The simulation is performed on the connected initial cells for two cases. The first case is for inverted (p-i-n)/(p-i-n) cells and the second is for the conventional (n-i-p)/(n-i-p) configuration. Both tandems are investigated in terms of the most important layer materials and parameters. After designing the current matching condition, the tandem PCEs are boosted to 21.52% and 19.14% for the inverted and conventional tandem cells, respectively. All TCAD device simulations are made by employing the Atlas device simulator given an illumination of AM1.5G (100 mW/cm2). This present study can offer design principles and valuable suggestions for eco-friendly solar cells made entirely of thin films, which can achieve flexibility for prospective use in wearable electronics.