Boosting the Charge Transport Property of Indeno[1,2‐b]fluorene‐6,12‐dione though Incorporation of Sulfur‐ or Nitrogen‐Linked Side Chains

Alkyl chains are basic units in the design of organic semiconductors for purposes of enhancing solubility, tuning electronic energy levels, and tailoring molecular packing. This work demonstrates that the carrier mobilities of indeno[1,2‐b ]fluorene‐6,12‐dione ( IFD )‐based semiconductors can be dramatically enhanced by the incorporation of sulfur‐ or nitrogen‐linked side chains. Three IFD derivatives possessing butyl, butylthio, and dibutylamino substituents are synthesized, and their organic field‐effect transistors (OFET) are fabricated and characterized. The IFD possessing butyl substituents exhibits a very poor charge transport property with mobility lower than 10^?7 cm² V^?1 s^?1. In contrast, the hole mobility is dramatically increased to 1.03 cm² V^?1 s^?1 by replacing the butyl units with dibutylamino groups ( DBA‐IFD ), while the butylthio‐modified IFD ( BT‐IFD ) derivative exhibits a high and balanced ambipolar charge transport property with the maximum hole and electron mobilities up to 0.71 and 0.65 cm² V^?1 s^?1, respectively. Moreover, the complementary metal–oxide–semiconductor‐like inverters incorporated with the ambipolar OFETs shows sharp inversions with a maximum gain value up to 173. This work reveals that modification of the aromatic core with heteroatom‐linked side chains, such as alkylthio or dialkylamino, can be an efficient strategy for the design of high‐performance organic semiconductors.     

Molecular Packing‐Induced Transition between Ambipolar and Unipolar Behavior in Dithiophene‐4,9‐dione‐Containing Organic Semiconductors

By changing the packing motif of the conjugated cores and the thin‐film microstructures, unipolar organic semiconductors may be converted into ambipolar materials. A combined experimental and theoretical investigation is conducted on the thin‐film organic field‐effect transistors (OFETs) of three organic semiconductors that have the same conjugated core structure of s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐4,9‐dione but with different n‐alkyl groups. The optical and electrochemical measurements suggest that the three organic semiconductors have very similar energy levels; however, their OFETs exhibit dramatically different transport characteristics. Transistors based on compound 1a or 1c show ambipolar transport properties, while those based on compound 1b show p‐type unipolar behavior. Specifically, compound 1c is characterized as a good ambipolar semiconductor with the highest electron mobility of 0.22 cm² V^?1 s^?1 and the highest hole mobility of 0.03 cm² V^?1 s^?1. Complementary metal oxide semiconductor (CMOS) inverters incorporated with compound 1c show sharp inversions with high gains above 50. Theoretical investigations reveal that the drastic difference in the transport properties of the three materials is due to the difference in their molecular packing and film microstructures.     

Gradual Controlling the Work Function of Metal Electrodes by Solution‐Processed Mixed Interlayers for Ambipolar Polymer Field‐Effect Transistors and Circuits

In this paper, a technique using mixed transition‐metal oxides as contact interlayers to modulate both the electron‐ and hole‐injections in ambipolar organic field‐effect transistors (OFETs) is presented. The cesium carbonate (Cs₂CO₃) and vanadium pentoixide (V₂O₅) are found to greatly and independently improve the charge injection properties for electrons and holes in the ambipolar OFETs using organic semiconductor of diketopyrrolopyrrolethieno[3,2‐b]thiophene copolymer (DPPT‐TT) and contact electrodes of molybdenum (Mo). When Cs₂CO₃ and V₂O₅ are blended at various mixing ratios, they are observed to very finely and constantly regulate the Mo's work function from ?4.2 eV to ?4.8 eV, leading to high electron‐ and hole‐mobilities as high as 2.6 and 2.98 cm² V^?1 s^?1, respectively. The most remarkable finding is that the device characteristics and device performance can be gradually controlled by adjusting the composition of mixed‐oxide interlayers, which is highly desired for such applications as complementary circuitry that requires well matched n‐channel and p‐channel device operations. Therefore, such simple interface engineering in conjunction with utilization of ambipolar semiconductors can truly enable the promising low‐cost and soft organic electronics for extensive applications.     

Alkoxy‐Functionalized Thienyl‐Vinylene Polymers for Field‐Effect Transistors and All‐Polymer Solar Cells

π‐conjugated polymers based on the electron‐neutral alkoxy‐functionalized thienyl‐vinylene (TVTOEt) building‐block co‐polymerized, with either BDT (benzodithiophene) or T2 (dithiophene) donor blocks, or NDI (naphthalenediimide) as an acceptor block, are synthesized and characterized. The effect of BDT and NDI substituents (alkyl vs alkoxy or linear vs branched) on the polymer performance in organic thin film transistors (OTFTs) and all‐polymer organic photovoltaic (OPV) cells is reported. Co‐monomer selection and backbone functionalization substantially modifies the polymer MO energies, thin film morphology, and charge transport properties, as indicated by electrochemistry, optical spectroscopy, X‐ray diffraction, AFM, DFT calculations, and TFT response. When polymer P7 is used as an OPV acceptor with PTB7 as a donor, the corresponding blend yields TFTs with ambipolar mobilities of μ_e = 5.1 × 10^?3 cm² V^–1 s^–1 and μ_h = 3.9 × 10^?3 cm² V^–1 s^–1 in ambient, among the highest mobilities reported to date for all‐polymer bulk heterojunction TFTs, and all‐polymer solar cells with a power conversion efficiency (PCE) of 1.70%, the highest reported PCE to date for an NDI‐polymer acceptor system. The stable transport characteristics in ambient and promising solar cell performance make NDI‐type materials promising acceptors for all‐polymer solar cell applications.     

Visible‐Near Infrared Absorbing Polymers Containing Thienoisoindigo and Electron‐Rich Units for Organic Transistors with Tunable Polarity

Systematic creation of polymeric semiconductors from novel building blocks is critical for improving charge transport properties in organic field‐effect transistors (OFETs). A series of ultralow‐bandgap polymers containing thienoisoindigo (TIIG) as a thiophene analogue of isoindigo (IIG) is synthesized. The UV‐Vis absorptions of the TIIG‐based polymers ( PTIIG‐T , PTIIG‐Se , and PTIIG‐DT ) exhibit broad bands covering the visible to near‐infrared range of up to 1600 nm. All the polymers exhibit unipolar p‐channel operations with regard to gold contacts. PTIIG‐DT with centrosymmetric donor exhibits a maximum mobility of 0.20 cm² V^?1 s^?1 under gold contacts, which is higher than those of the other polymers containing axisymmetric donors. Intriguingly, OFETs fabricated with aluminum electrodes show ambipolar charge transport with hole and electron mobilities of up to 0.28 ( PTIIG‐DT ) and 0.03 ( PTIIG‐T ) cm² V^?1 s^?1, respectively. This is a record value for the hitherto reported TIIG‐based OFETs. The finding demonstrates that TIIG‐based polymers can potentially function as either unipolar or ambipolar semiconductors without reliance on the degree of electron affinity of the co‐monomers.     

Quinoidal Molecules as a New Class of Ambipolar Semiconductor Originating from Amphoteric Redox Behavior

The two small molecules, quinoidal bithiophene (QBT) and quinoidal biselenophene (QBS), are designed based on a quinoid structure, and synthesized via a facile synthetic route. These quinoidal molecules have a reduced band gap and an amphoteric redox behavior, which is caused by an extended delocalization. Due to such properties, organic field‐effect transistors based on QBT and QBS have shown balanced ambipolar characteristics. After thermal annealing, the performances of the devices are enhanced by an increase in crystallinity. The field‐effect hole and electron mobilities are measured to be 0.031 cm² V^?1 s^?1 and 0.005 cm² V^?1 s^?1 for QBT, and 0.055 cm² V^?1 s^?1 and 0.021 cm² V^?1 s^?1 for QBS, respectively. In addition, we investigate the effect of chalcogen atoms (S and Se) on the molecular properties. The optical, electrochemical properties and electronic structures are mainly dominated by the quinoidal structure, whereas molecular properties are scarcely affected by either type of chalcogen atom. The main effect of the chalcogen atoms is ascribed to the difference of crystallinity. Due to a strong intermolecular interaction of the selenophene, QBS exhibits a higher degree of crystallinity, which leads to an enhancement of both hole and electron mobilities. Consequently, these types of quinoidal molecules are found to be promising for use as ambipolar semiconductors.     

ε‐Branched Flexible Side Chain Substituted Diketopyrrolopyrrole‐Containing Polymers Designed for High Hole and Electron Mobilities

Based on the integrated consideration and engineering of both conjugated backbones and flexible side chains, solution‐processable polymeric semiconductors consisting of a diketopyrrolopyrrole (DPP) backbone and a finely modulated branching side chain (ε‐branched chain) are reported. The subtle change in the branching point from the backbone alters the π?π stacking and the lamellar distances between polymer backbones, which has a significant influence on the charge‐transport properties and in turn the performances of field‐effect transistors (FETs). In addition to their excellent electron mobilities (up to 2.25 cm² V^?1 s^?1), ultra‐high hole mobilities (up to 12.25 cm² V^?1 s^?1) with an on/off ratio (I_on/I_off) of at least 10⁶ are achieved in the FETs fabricated using the polymers. The developed polymers exhibit extraordinarily high electrical performance with both hole and electron mobilities superior to that of unipolar amorphous silicon.     

Highly Efficient Charge Transport in a Quasi‐Monolayer Semiconductor on Pure Polymer Dielectric

The study of monolayer organic field‐effect transistors (MOFETs) provides an effective way to investigate the intrinsic charge transport of semiconductors. To date, the research based on organic monolayers on polymeric dielectrics lays far behind that on inorganic dielectrics and the realization of a bulk‐like carrier mobility on pure polymer dielectrics is still a formidable challenge for MOFETs. Herein, a quasi‐monolayer coverage of pentacene film with orthorhombic phase is grown on the poly (amic acid) (PAA) dielectric layer. More significantly, charge density redistribution occurs at the interface between the pentacene and PAA caused by electron transfer from pentacene to the PAA dielectric layer, which is verified by theoretical simulations and experiments. As a consequence, an enhanced hole accumulation layer is formed and pentacene‐based MOFETs on pure polymer dielectrics exhibit bulk‐like carrier mobilities of up to 13.7 cm² V^?1 s^?1 from the saturation region at low V_GS, 9.1 cm² V^?1 s^?1 at high V_GS and 7.6 cm² V^?1 s^?1 from the linear region, which presents one of the best results of previously reported MOFETs so far and indicates that the monolayer semiconductor growing on pure polymer dielectric could produce highly efficient charge transport.     

Carrier Modulation of Ambipolar Few‐Layer MoTe2 Transistors by MgO Surface Charge Transfer Doping

Semiconducting molybdenum ditelluride (2H‐MoTe₂), a fast‐emerging 2D material with an appropriate band gap and decent carrier mobility, is configured as field‐effect transistors and is the focus of substantial research interest, showing hole‐dominated ambipolar characteristics. Here, carrier modulation of ambipolar few‐layer MoTe₂ transistors is demonstrated utilizing magnesium oxide (MgO) surface charge transfer doping. By carefully adjusting the thickness of MgO film and the number of MoTe₂ layers, the carrier polarity of MoTe₂ transistors from p‐type to n‐type can be reversely controlled. The electron mobility of MoTe₂ is significantly enhanced from 0.1 to 20 cm² V^?1 s^?1 after 37 nm MgO film doping, indicating a greatly improved electron transport. The effective carrier modulation enables to achieve high‐performance complementary inverters with high DC gain of >25 and photodetectors based on few‐layer MoTe₂ flakes. The results present an important advance toward the realization of electronic and optoelectronic devices based on 2D transition‐metal dichalcogenide semiconductors.     

Solution‐Processed High‐Performance Tetrathienothiophene‐Based Small Molecular Blends for Ambipolar Charge Transport

Four soluble dialkylated tetrathienoacene ( TTAR) ‐based small molecular semiconductors featuring the combination of a TTAR central core, π‐conjugated spacers comprising bithiophene ( bT ) or thiophene ( T ), and with/without cyanoacrylate ( CA ) end‐capping moieties are synthesized and characterized. The molecule DbT‐TTAR exhibits a promising hole mobility up to 0.36 cm² V^?1 s^?1 due to the enhanced crystallinity of the microribbon‐like films. Binary blends of the p‐type DbT‐TTAR and the n‐type dicyanomethylene substituted dithienothiophene‐quinoid ( DTTQ‐11 ) are investigated in terms of film morphology, microstructure, and organic field‐effect transistor (OFET) performance. The data indicate that as the DbT‐TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron‐only) to ambipolar and then back to unipolar (hole‐only). With a 1:1 weight ratio of DbT‐TTAR DTTQ‐11 in the blend, well‐defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm² V^?1 s^?1, respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high‐performance solution‐processable OFETs.     

Solution‐Processed Small‐Molecule Bulk Heterojunction Ambipolar Transistors

Solution‐processed small‐molecule bulk heterojunction (BHJ) ambipolar organic thin‐film transistors are fabricated based on a combination of [2‐phenylbenzo[d,d']thieno[3,2‐b;4,5‐b']dithiophene (P‐BTDT) : 2‐(4‐n‐octylphenyl)benzo[d,d ']thieno[3,2‐b;4,5‐b']dithiophene (OP‐BTDT)] and C₆₀. Treating high electrical performance vacuum‐deposited P‐BTDT organic semiconductors with a newly developed solution‐processed organic semiconductor material, OP‐BTDT, in an optimized ratio yields a solution‐processed p‐channel organic semiconductor blend with carrier mobility as high as 0.65 cm² V^?1 s^?1. An optimized blending of P‐BTDT:OP‐BTDT with the n‐channel semiconductor, C₆₀, results in a BHJ ambipolar transistor with balanced carrier mobilities for holes and electrons of 0.03 and 0.02 cm² V^?1 s^?1, respectively. Furthermore, a complementary‐like inverter composed of two ambipolar thin‐film transistors is demonstrated, which achieves a gain of 115.     

Ambipolar Charge Transport in Air‐Stable Polymer Blend Thin‐Film Transistors

Ambipolar thin‐film transistors based on a series of air‐stable, solution‐processed blends of an n‐type polymer poly(benzobisimidazobenzophenanthroline) (BBL) and a p‐type small molecule, copper phthalocyanine (CuPc) are demonstrated, where all fabrication and measurements are performed under ambient conditions. The hole mobilities are in the range of 6.0 × 10^–6 to 2.0 × 10^–4 cm² V^–1 s^–1 and electron mobilities are in the range of 2.0 × 10^–6 to 3.0 × 10^–5 cm² V^–1 s^–1, depending on the blend composition. UV‐vis spectroscopy and electron diffraction show crystallization of CuPc in the metastable α‐crystal form within the semicrystalline BBL matrix. These CuPc domains develop into elongated ribbon‐like crystalline nanostructures when the blend films are processed in methanol, but not when they are processed in water. On methylene chloride vapor annealing of the blend films, a phase transformation of CuPc from the α‐form to the β‐form is observed, as shown by optical absorption spectroscopy and electron diffraction. Ambipolar charge transport is only observed in the blend films where CuPc crystallized in the elongated ribbon‐like nanostructures (α‐form). Ambipolar behavior is not observed with CuPc in the β‐polymorph. Unipolar hole mobilities as high as 2.0 × 10^–3 cm² V^–1 s^–1 are observed in these solution‐processed blend field‐effect transistors (FETs) on prolonged treatment in methanol, comparable to previously reported hole mobilities in thermally evaporated CuPc FETs. These results show that ambipolar charge transport and carrier mobilities in multicomponent organic semiconductors are intricately related to the phase‐separated nanoscale and crystalline morphology.     

Tuning the Charge Carrier Polarity of Organic Transistors by Varying the Electron Affinity of the Flanked Units in Diketopyrrolopyrrole‐Based Copolymers

Fine‐tuning of the charge carrier polarity in organic transistors is an important step toward high‐performance organic complementary circuits and related devices. Here, three new semiconducting polymers, namely, pDPF‐DTF2, pDPSe‐DTF2, and pDPPy‐DTF2, are designed and synthesized using furan, selenophene, and pyridine flanking group‐based diketopyrrolopyrrole cores, respectively. Upon evaluating their electrical properties in transistor devices, the best performance has been achieved for pDPSe‐DTF2 with the highest and average hole mobility of 1.51 and 1.22 cm² V^?1 s^?1, respectively. Most intriguingly, a clear charge‐carrier‐polarity change is observed when the devices are measured under vacuum. The pDPF‐DTF2 polymer exhibits a balanced ambipolar performance with the µ_h/µ_e ratio of 1.9, whereas pDPSe‐DTF2 exhibits p‐type dominated charge carrier transport properties with the µ_h/µ_e ratio of 26.7. Such a charge carrier transport change is due to the strong electron‐donating nature of the selenophene. Furthermore, pDPPy‐DTF2 with electron‐withdrawing pyridine flanking units demonstrates unipolar n‐type charge transport properties with an electron mobility as high as 0.20 cm² V^?1 s^?1. Overall, this study demonstrates a simple yet effective approach to switch the charge carrier polarity in transistors by varying the electron affinity of flanking groups of the diketopyrrolopyrrole unit.     

High‐Performance Ambipolar Polymers Based on Electron‐Withdrawing Group Substituted Bay‐Annulated Indigo

For donor–acceptor conjugated polymers, it is an effective strategy to improve their electron mobilities by introducing electron‐withdrawing groups (EWGs, such as F, Cl, or CF₃) into the polymer backbone. However, the introduction of different EWGs always requires a different synthetic approach, leading to additional arduous work. Here, an effective two‐step method is developed to obtain EWG substituted bay‐annulated indigo (BAI) units. This method is effective to introduce various EWGs (F, Cl, or CF₃) into BAI at different substituted positions. Based on this method, EWG substituted BAI acceptors, including 2FBAI, 2ClBAI, and 2CF₃BAI, are reported for the first time. Furthermore, four polymers of PBAI‐V, P2FBAI‐V, P2ClBAI‐V, and P4OBAI‐V are developed. All the polymers show ambipolar transport properties. Particularly, P2ClBAI‐V exhibits remarkable hole and electron mobilities of 4.04 and 1.46 cm² V^?1 s^?1, respectively. These mobilities are among the highest values for BAI‐based polymers.     

High‐Performance,Low‐Operating‐Voltage Organic Field‐Effect Transistors with Low Pinch‐Off Voltages

Organic field‐effect transistors suffer from ultra‐high operating voltages in addition to their relative low mobility. A general approach to low‐operating‐voltage organic field‐effect transistors (OFETs) using donor/acceptor buffer layers is demonstrated. P‐type OFETs with acceptor molecule buffer layers show reduced operating voltages (from 60–100 V to 10–20 V), with mobility up to 0.19 cm² V^?1 s^?1 and an on/off ratio of 3 × 10⁶. The subthreshold slopes of the devices are greatly reduced from 5–12 V/decade to 1.68–3 V/decade. This favorable combination of properties means that such OFETs can be operated successfully at voltages below 20 V (|V_DS| ≤ 20 V, |V_GS| ≤ 20 V). This method also works for n‐type semiconductors. The reduced operating voltage and low pinch‐off voltage contribute to the improved ordering of the polycrystalline films, reduced grain boundary resistance, and steeper subthreshold slopes.     

Stable Delocalized Singlet Biradical Hydrocarbon for Organic Field‐Effect Transistors

Delocalized singlet biradical hydrocarbons hold promise as new semiconducting materials for high‐performance organic devices. However, to date biradical organic molecules have attracted little attention as a material for organic electronic devices. Here, this work shows that films of a crystallized diphenyl derivative of s‐indacenodiphenalene (Ph₂‐IDPL) exhibit high ambipolar mobilities in organic field‐effect transistors (OFETs). Furthermore, OFETs fabricated using Ph₂‐IDPL single crystals show high hole mobility (μ_h = 7.2 × 10^?1 cm² V^?1 s^?1) comparable to that of amorphous Si. Additionally, high on/off ratios are achieved for Ph₂‐IDPL by inserting self‐assembled mono­layer of alkanethiol between the semiconducting layer and the Au electrodes. These findings open a door to the application of ambipolar OFETs to organic electronics such as complementary metal oxide semiconductor logic circuits.     

Ambient‐Stable,Annealing‐Free,and Ambipolar Organic Field‐Effect Transistors Based on Solution‐Processable Poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene) without Long Alkyl Side Chains

An ambipolar conjugated polymer CF₃‐PBTV, poly(2,2′‐bis(trifluoromethyl)biphenyl‐alt‐2,5‐divinylthiophene), consisting of thienylenevinylene as the donor and trifluoromethyl‐substituted biphenyl as the acceptor has been successfully synthesized. CF₃‐PBTV shows solution‐processability without electrically insulating long alkyl side chains. Grazing incidence X‐ray diffraction results suggest a nearly equal population of flat‐on and end‐on domains in CF₃‐PBTV thin film. The excellent ambipolarity of CF₃‐PBTV is demonstrated by well‐equivalent charge mobilities of 0.065 and 0.078 cm² V^?1 s^?1 for p‐ and n‐channel, respectively. The organic field‐effect transistors (OFET) also shows very high on/off ratio (≈10⁷) which is attributed to the relatively large bandgap and low‐lying highest occupied molecular orbital (HOMO) of CF₃‐PBTV. The OFET performance barely changes after the device is stored in ambient conditions for 90 days. The ambient‐stability is attributed to the enhanced oxidative stability from its low‐lying HOMO and the better moisture resistance from its fluorine contents. The performance of CF₃‐PBTV based OFET is annealing independent. It is noteworthy that the solution‐processable, ambipolar, and thienylenevinylene‐containing conjugated polymer without any long alkyl side chains is reported for the first time. And to the best of our knowledge, it is the first ambient‐stable, annealing‐free OFET with well‐equivalent ambipolarity.     

Layer‐by‐Layer Conjugated Extension of a Semiconducting Polymer for High‐Performance Organic Field‐Effect Transistor

A donor–acceptor (D–A) semiconducting copolymer, PDPP‐TVT‐29, comprising a diketopyrrolopyrrole (DPP) derivative with long, linear, space‐separated alkyl side‐chains and thiophene vinylene thiophene (TVT) for organic field‐effect transistors (OFETs) can form highly π‐conjugated structures with an edge‐on molecular orientation in an as‐spun film. In particular, the layer‐like conjugated film morphologies can be developed via short‐term thermal annealing above 150 °C for 10 min. The strong intermolecular interaction, originating from the fused DPP and D–A interaction, leads to the spontaneous self‐assembly of polymer chains within close proximity (with π‐overlap distance of 3.55 Å) and forms unexpectedly long‐range π‐conjugation, which is favorable for both intra‐ and intermolecular charge transport. Unlike intergranular nanorods in the as‐spun film, well‐conjugated layers in the 200 °C‐annealed film can yield more efficient charge‐transport pathways. The granular morphology of the as‐spun PDPP‐TVT‐29 film produces a field‐effect mobility (μ _FET) of 1.39 cm² V^?1 s^?1 in an OFET based on a polymer‐treated SiO₂ dielectric, while the 27‐Å‐step layered morphology in the 200 °C‐annealed films shows high μ _FET values of up to 3.7 cm² V^?1 s^?1.     

A Timely Synthetic Tailoring of Biaxially Extended Thienylenevinylene‐Like Polymers for Systematic Investigation on Field‐Effect Transistors

Considering there is growing interest in the superior charge transport in the (E)‐2‐(2‐(thiophen‐2‐yl)‐vinyl)thiophene (TVT)‐based polymer family, an essential step forward is to provide a deep and comprehensive understanding of the structure–property relationships with their polymer analogs. Herein, a carefully chosen set of DPP‐TVT‐n polymers are reported here, involving TVT and diketopyrrolopyrrole (DPP) units that are constructed in combination with varying thiophene content in the repeat units, where n is the number of thiophene spacer units. Their OFET characteristics demonstrate ambipolar behavior; in particular, with DPP‐TVT‐0 a nearly balanced hole and electron transport are observed. Interestingly, the majority of the charge‐transport properties changed from ambipolar to p‐type dominant, together with the enhanced hole mobilities, as the electron‐donating thiophene spacers are introduced. Although both the lamellar d‐spacings and π‐stacking distances of DPP‐TVT‐n decreased with as the number of thiophene spacers increased, DPP‐TVT‐1 clearly shows the highest hole mobility (up to 2.96 cm² V^?1 s^?1) owing to the unique structural conformations derived from its smaller paracrystalline distortion parameter and narrower plane distribution relative to the others. These in‐depth studies should uncover the underlying structure–property relationships in a relevant class of TVT‐like semiconductors, shedding light on the future design of top‐performing semiconducting polymers.     

Inversion of Dominant Polarity in Ambipolar Polydiketopyrrolopyrrole with Thermally Removable Groups

A narrow bandgap polymeric semiconductor, BOC‐PTDPP , comprising alkyl substituted diketopyrrolopyrrole (DPP) and tert‐butoxycarbonyl (t‐BOC)‐protected DPP, is synthesized and used in organic field‐effect transistors (OFETs). The polymer films are prepared by solution deposition and thermal annealing of precursors featuring thermally labile t‐BOC groups. The effects of the thermal cleavage on the molecular packing structure in the polymer thin films are investigated using thermogravimetric analysis (TGA), UV‐vis spectroscopy, atomic force microscopy (AFM), Fourier transform infrared (FT‐IR) spectroscopy, and X‐ray diffraction (XRD) analysis. Upon utilization of solution‐shearing process, integrating the ambipolar BOC‐PTDPP into transistors shows p‐channel dominant characteristics, resulting in hole and electron mobilities as high as 1.32 × 10^?2 cm² V^?1 s^?1 and 2.63 × 10^?3 cm² V^?1 s^?1, which are about one order of magnitude higher than those of the drop‐cast films. Very intriguingly, the dominant polarity of charge carriers changes from positive to negative after the thermal cleavage of t‐BOC groups at 200 °C. The solution‐sheared films upon subsequent thermal treatment show superior electron mobility (μ_e = 4.60 × 10^?2 cm² V^?1 s^?1), while the hole mobility decreases by one order of magnitude (μ_h = 4.30 × 10^?3 cm² V^?1 s^?1). The inverter constructed with the combination of two identical ambipolar OFETs exhibits a gain of ～10. Reported here for the first time is a viable approach to selectively tune dominant polarity of charge carriers in solution‐processed ambipolar OFETs, which highlights the electronically tunable ambipolarity of thermocleavable polymer by simple thermal treatment.