自 2012 年《聚合物科学杂志》上发表关于聚合物电子学的特刊以来，已经过去了十年。半导体聚合物领域取得了许多突破。例如，据三菱化学公司报告，2011 年聚合物太阳能电池的创纪录功率转换效率 (PCE) 为 9.2%。你15%，便宜又用料丰富。” 1到 2021 年，不仅实现了 15% 的效率，而且该领域也已从聚合物-富勒烯太阳能电池转向非富勒烯受体。基于 PM6 半导体聚合物和 Y6 非富勒烯受体的最新发展为单层太阳能电池提供了 18% 的 PCE。2同样，随着聚合物太阳能电池的进步，基于聚合物的场效应晶体管、热电器件和电致变色器件都在技术开发和商业化方面取得了重大进展。此外，该领域在过去几年也经历了混合离子和电子导体的复兴。因此，它激励我们组织第二期关于半导体聚合物的特刊，并邀请活跃的研究人员分享他们在该领域的观点和研究进展。在本期特刊中，它包含 20 篇文章，涉及聚合物设计和合成、建模、表征、加工和应用。

聚合物设计和合成是塑料电子产品的主要驱动力和基础。能等。概述了用于有机电子器件的内酰胺基聚合物半导体的最新进展。内酰胺是供体-受体半导体聚合物中许多主要电子受体的关键部分，例如二酮吡咯并[3,4-c]吡咯 (DPP)、萘二亚胺 (NDI)、异靛蓝 (IID)、2,2-联噻吩-3 ,3-二甲酰亚胺 (BTI) 和噻吩并[3,4-c]吡咯-4,6-二酮 (TPD)。作者查阅了文献，得出的结论是，过去 3 年，新型内酰胺基聚合物的开发没有显着进展，DPP 基聚合物仍占主导地位。他们还指出批次间的变化、可扩展性、和可加工性是社区必须解决的关键问题，以推动聚合物电子学的发展。Thompson 等人对直接芳基化聚合 (DArP) 的综述。部分解决了聚合物的可扩展性问题。通过规避单体，使用 Stille-Migita 和 Suzuki-Miyaura 聚合方法所需的有机锡烷和有机硼等有毒金属转移试剂进行功能化，DArP 通过金属催化的 CH 活化途径进行制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。Thompson 等人对直接芳基化聚合 (DArP) 的综述。部分解决了聚合物的可扩展性问题。通过规避单体，使用 Stille-Migita 和 Suzuki-Miyaura 聚合方法所需的有机锡烷和有机硼等有毒金属转移试剂进行功能化，DArP 通过金属催化的 CH 活化途径进行制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。Thompson 等人对直接芳基化聚合 (DArP) 的综述。部分解决了聚合物的可扩展性问题。通过规避单体，使用 Stille-Migita 和 Suzuki-Miyaura 聚合方法所需的有机锡烷和有机硼等有毒金属转移试剂进行功能化，DArP 通过金属催化的 CH 活化途径进行制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。通过规避单体，使用 Stille-Migita 和 Suzuki-Miyaura 聚合方法所需的有机锡烷和有机硼等有毒金属转移试剂进行功能化，DArP 通过金属催化的 CH 活化途径进行制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。通过规避单体，使用 Stille-Migita 和 Suzuki-Miyaura 聚合方法所需的有机锡烷和有机硼等有毒金属转移试剂进行功能化，DArP 通过金属催化的 CH 活化途径进行制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。DArP 通过金属催化的 CH 活化途径制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。DArP 通过金属催化的 CH 活化途径制备高性能半导体聚合物。这篇综述强调了在为 DArP 开发更可持续的第一行过渡金属催化剂方面的最新进展。它强调需要追求下一代催化设计，以实现更有效和环保的半导体聚合物合成。

本期特刊介绍了几个突出侧链工程的半导体聚合物分子设计示例。Rondeau-Gagné 等人。报告了将聚酰胺胺 (PAMAM) 树枝状侧链结合到基于 DPP 的半结晶聚合物中对其光电、热机械和固态性能的影响。裴等人。利用混合脂肪族和低聚（乙二醇）侧链来调节 3,7-bis((E)-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3 的聚集行为， 7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione (FBDPPV) 并研究侧链比率对掺杂效率的影响。萨瓦等人。对混合侧链进行第一次专门的粗粒度分子动力学研究。他们的模拟概括了当大部分疏水侧链在超过约 40% 极性侧链的阈值后结合到电解质膨胀的形态中时，界面门控电解质形态的非线性进展。张等人。提出了在侧链中使用香豆素基团来赋予基于 DPP 的半导体聚合物的愈合能力和热稳定性。努南等人。揭示酯侧基区域化学的影响，并强调侧基如何影响聚呋喃的构象性质和稳定性。米肖德尔等人。证明侧链在带有直链烷基取代基或支链烷氧基取代基的 [2.2] 对环芳二烯的立体保持性开环复分解聚合 (ROMP) 中起关键作用。2-乙基己氧基侧链的引入允许制备具有异常高摩尔质量的PPV用于活性聚合。暴露于紫外光 (365 nm) 会迅速诱导全顺式烯烃异构化，从而形成全反式 PPV。它与其辛基对应物形成鲜明对比，后者发生缓慢的聚合和光异构化。

主链工程在现阶段不像侧链工程那样流行，但近年来人们对梯型半导体聚合物和共轭断裂半导体聚合物的兴趣有所增加。梯形聚合物由一系列稠合的 π 共轭环组成，具有两条或多条键链。作者从方和顾的角度介绍了聚合物链刚度的基本概念，以及相应的实验方法、模型和模拟。随后，他们用常规半导体聚合物和梯形聚合物的代表性例子分析了链的刚性。他们还分享了描述和预测链构象、对结构缺陷的综合控制以及刚性与应用的相关性的见解。在单独的工作中，顾等人。系统地研究了共轭断裂间隔物 (CBS) 对串联 n 型萘二亚胺基 (PNDI) 共轭聚合物热机械性能的影响。发现 CBS 可以显着降低链刚度、熔点以及玻璃化转变温度，并进一步研究了 CBS 对 PNDI-C3 至 C6 结晶行为的影响，包括等温结晶动力学、晶体多晶型和随后的时间-依赖模量。作者得出结论，调整骨架刚度可能是调整柔性电子产品聚合物机械性能的有效方法。里斯科等人。进行大规模原子分子动力学模拟，以检查结合到 DPP 聚合物骨架中的 CBS 对聚合物结构、动力学、和热性能。他们发现，较长的烷基链段会导致聚合物链更灵活、更紧凑、更具流动性，并且凝聚相的玻璃化转变温度更低。

半导体聚合物的应用已被广泛覆盖。安德鲁等人。提供他们对用于灵活光控制和热管理的可持续聚合物材料的看法。作者还阐明了与其他纳米材料相比，半导体聚合物的优缺点。用半导体聚合物功能化的服装可以显着降低室内供暖和制冷成本，有助于节能和温度调节技术，以应对全球能源和气候危机。陈和 Ercan 等人。分享了他们使用聚（9,9-二辛基芴）（PFO）-嵌段-聚（乙烯基苯基恶二唑）（POXD）共轭嵌段共聚物的光子场效应晶体管（FET）存储器件的最新研究进展。通过优化嵌段共聚物中的 POXD 含量，记忆比（I在 10 4之后实现了 ~10 5的ON /I OFF ) s，表明其优越的长期稳定性和数据可辨别性。光子晶体管存储设备中的这种驻极体开辟了开发光子存储器、人类感知和未来通信系统的可能性。迪等人。系统回顾了基于聚合物材料的可植入电子传感器的发展。他们还调查了将聚合物与可植入传感器集成的策略，包括设备接口、几何形状和集成。深入了解聚合物在可植入传感器中的作用，为开发具有长期稳定性和超灵敏体内传感的安全、多功能和多尺寸电子设备铺平了道路。随着这些植入式传感器的开发，准确和动态的健康状况监测可以进一步帮助医生在未来提供定制的医疗保健建议。赵和刘等人。总结基于聚合物的有机电路的最新进展，从逻辑门等数字电路到放大器等模拟电路。作者指出了在有机电路成为现实之前需要克服的一些障碍。其中包括缺乏涵盖各种有机半导体的精确和通用的电荷传输模型，这使得电路设计人员难以模拟器件和电路行为、缺乏可重复性以及器件的批次间差异。作者指出了在有机电路成为现实之前需要克服的一些障碍。其中包括缺乏涵盖各种有机半导体的精确和通用的电荷传输模型，这使得电路设计人员难以模拟器件和电路行为、缺乏可重复性以及器件的批次间差异。作者指出了在有机电路成为现实之前需要克服的一些障碍。其中包括缺乏涵盖各种有机半导体的精确和通用的电荷传输模型，这使得电路设计人员难以模拟器件和电路行为、缺乏可重复性以及器件的批次间差异。

近年来，基于混合导体的有机电化学晶体管（OECT）受到关注，并被广泛考虑用于生物传感和神经形态计算。3雷等人。分析高性能OECT材料的分子设计策略，突出主链设计和侧链工程的特点和效果。他们讨论了一些被忽视和未解决的问题，例如缺乏高性能 n 型聚合物和评估聚合物性能的标准化方法，同时为未来的 OECT 研究提供了展望。哦等。概述了基于半导体聚合物的神经形态器件及其在神经形态生物电子学中的应用。他们特别关注模拟神经通信行为的基于半导体聚合物的三端人工突触的最新进展。他们设想，基于半导体聚合物的神经形态生物电子学的快速发展将加速人机界面系统的商业化，包括智能假肢和可植入诊断设备。聚 (3,4-乙烯二氧噻吩) (PEDOT) 是最著名和研究的混合导体，具有良好的性能。它通常用作生物传感器、OECT、神经形态生物电子学和电致变色器件中的活性材料。然而，PEDOT 有几个缺点，这可能会限制其有效性或长期使用，包括对 ITO 涂层玻璃等基材的附着力较弱、表面形态控制不佳以及随时间推移降低电化学稳定性。尼尔森等人。展示了一种基于共价改性 EDOT (PEDOT-Crown) 的新型聚合物，具有极性图案和 15-crown-5 部分。他们表明，PEDOT-Crown 具有丰富的优势特性，包括在物理和电化学胁迫下对 ITO 的优异附着力；更均匀的表面形态；和电化学特性，包括更高的对比度、红移极化子和双极化子吸收特征、​​在更窄的电压范围内中性吸收带的漂白以及更多的法拉第而不是电容行为。这项研究证明了分子设计是将混合导体推向实际应用的有效策略，而 Graham 等人的结果。证明了解掺杂过程在这些应用中同样重要。作者研究了反离子结构如何影响电化学掺杂能力、氧化电位、区域规则 (rr) 和区域随机 (rra) P3HT 的电离能和极化子吸光度。发现阴离子也会导致极化子吸光度和电离能的显着差异，从而强调了抗衡离子在确定掺杂 π 共轭聚合物的光学和电子特性方面的关键作用。

除了聚合物薄膜电子产品，3D 打印电子产品也应运而生。Chortos 回顾了用于生物界面、软机器人和能量存储的共轭聚合物的挤出 3D 打印。它总结了 3D 打印半导体聚合物新兴领域的进展，使用了三种挤压打印工艺：直接墨水书写、弯月面引导打印和电流体动力打印。深入描述了直接写入的墨水设计，包括修改墨水流变性和导电性的策略。

从阅读这些评论和研究进展可以看出，半导体聚合物领域已经发展到了一个新的水平。半导体聚合物的下一步是什么？首先，社区必须解决聚合物合成中的可重复性、可扩展性和可持续性问题。非常希望有受控的聚合方法，以尽量减少导致不良再现性的副反应。制备聚合物所需的步骤越多，商业采用的可能性就越小。有毒试剂和溶剂的使用也将禁止材料和装置的采用。在分子设计阶段必须考虑可持续性。其次，社区必须开发受控的薄膜形成和图案化工艺。卷对卷制造是基于聚合物的柔性电子产品的最大特点之一，可显着降低成本。然而，大面积的均匀涂层提出了重大挑战。它需要深入了解溶液中的聚合物聚集体、流体动力学和干燥动力学。第三，社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。这大大降低了成本。然而，大面积的均匀涂层提出了重大挑战。它需要深入了解溶液中的聚合物聚集体、流体动力学和干燥动力学。第三，社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。这大大降低了成本。然而，大面积的均匀涂层提出了重大挑战。它需要深入了解溶液中的聚合物聚集体、流体动力学和干燥动力学。第三，社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。大面积的均匀涂层是一项重大挑战。它需要深入了解溶液中的聚合物聚集体、流体动力学和干燥动力学。第三，社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。大面积的均匀涂层是一项重大挑战。它需要深入了解溶液中的聚合物聚集体、流体动力学和干燥动力学。第三，社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。社区必须开发一个理论模型来精确描述聚合物薄膜的电荷传输行为，这是电路设计的先决条件。第四，有必要更好地了解聚合物降解和设备故障模式。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。此类研究目前尚不可用，但对于柔性电子产品的技术发展至关重要。最后但并非最不重要的一点是，将半导体聚合物和聚合物电子产品推向市场需要多学科的努力。

"点击查看英文标题和摘要"

A decade has passed since a special issue on polymer electronics appeared in the Journal of Polymer Science in 2012. The field of semiconducting polymers has witnessed many breakthroughs. For instance, the record power conversion efficiency (PCE) for polymer solar cells was 9.2% in 2011, reported by Mitsubishi Chemical Corp. Michael McGehee, an expert in polymer cells, had wished that “the door is still open for a technology that gives you 15%, is cheap and uses abundant materials.”1 By 2021, not only 15% efficiency has been achieved, but also the field has moved from polymer-fullerene solar cells to nonfullerene acceptors. The latest development based on PM6 semiconducting polymers and Y6 nonfullerene acceptors offers PCEs of 18% for single-layered solar cells.2 Similarly, with the advancement of polymer solar cells, polymer-based field-effect transistors, thermoelectrics, and electrochromics all have made a significant stride towards technology development and commercialization. In addition, the field has also experienced the renaissance of mixed ionic and electronic conductors over the past few years. Thus, it motivates us to organize the second special issue on semiconducting polymers and invite active researchers to share their perspectives and research progress in this field. In this special issue, it contains 20 contributions, ranging from polymer design and synthesis, modeling, characterization, processing, and applications.

Polymer design and synthesis are the major driving force and the foundation for plastic electronics. Noh et al. provide an overview of recent progress in lactam-based polymer semiconductors for organic electronic devices. Lactams are a key moiety in many leading electron acceptors in donor-acceptor semiconducting polymers, such as diketopyrrolo[3,4-c]pyrrole (DPP), naphthalene diimide (NDI), isoindigo (IID), 2,2-bithiophene-3,3-dicarboximide (BTI), and thieno[3,4-c]pyrrole-4,6-dione (TPD). The authors surveyed the literature and concluded that there had been no remarkable progress on the development of new lactam-based polymers in the past 3 years, and DPP-based polymers still dominate the field. They also point out that batch-to-batch variation, scalability, and processability are critical issues the community has to address in order to advance polymer electronics. A review on direct arylation polymerization (DArP) by Thompson et al. partially addresses the polymer scalability issue. By circumventing monomer, functionalization with toxic transmetallation reagents such as organostannane and organoboron required for Stille-Migita and Suzuki-Miyaura polymerization methods, DArP proceeds through a metal-catalyzed C-H activation pathway for the preparation of high-performance semiconducting polymers. This review highlighted recent advances in developing more sustainable first-row transition metal catalysts for DArP. It emphasizes the need to pursue the next generation of catalytic design to enable a more effective and environmentally friendly synthesis of semiconducting polymers.

Several examples of molecular design of semiconducting polymers that highlight side-chain engineering are presented in this special issue. Rondeau-Gagné et al. report the effect of incorporating polyamidoamine (PAMAM) dendritic side chains to DPP-based semicrystalline polymers on their optoelectronic, thermomechanical, and solid-state properties. Pei et al. utilize mixed aliphatic and oligo(ethylene glycol) side chains to modulate the aggregation behaviors of 3,7-bis((E)-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b’]difuran-2,6-dione (FBDPPV) and study the impact of side chain ratios on doping efficiency. Savoie et al. perform the first dedicated coarse-grained molecular dynamics study of mixed side chains. Their simulations recapitulate the nonlinear progression of the morphology from an interfacially gated electrolyte when large fractions of hydrophobic side-chains are incorporated to an electrolyte-swelled morphology after crossing a threshold of approximately 40% polar side-chains. Zhang et al. present the use of coumarin groups in the side chains to render healing ability and thermal stability to DPP-based semiconducting polymers. Noonan et al. reveal the impact of ester side group regiochemistry and highlight how side groups can impact conformational properties and stability of polyfurans. Michaudel et al. demonstrate that side chain plays a critical role in stereoretentive ring-opening metathesis polymerization (ROMP) of [2.2]paracyclophane dienes bearing either a linear alkyl substituent or a branched alkoxy substituent. The introduction of a 2-ethylhexyloxy side chain permits the PPV preparation with uncharacteristically high molar masses for living polymerization. Exposure to UV light (365 nm) rapidly induces isomerization of all-cis alkenes leading to the formation of all-trans PPV. It is a stark contrast to its octyl counterpart, in which slow polymerization and photoisomerization occur.

Backbone engineering is not as popular as side-chain engineering at the current stage, but interest in ladder-type semiconducting polymers and conjugation-break semiconducting polymers have buoyed in recent years. A ladder polymer is composed of a sequence of fused π-conjugated rings featuring two or more strands of bonds. In Fang's and Gu's perspective, the authors introduce the fundamental concepts on polymer chain rigidity, as well as the corresponding experimental methods, models, and simulations. Subsequently, they analyze chain rigidity with representative examples of regular semiconducting polymers and ladder polymers. They also share insight into describing and predicting chain conformation, synthetic control on structural defects, and the correlation of rigidity with applications. In separate work, Gu et al. systematically investigate the influence of conjugation break spacers (CBS) on the thermomechanical properties of a series n-type naphthalene diimide-based (PNDI) conjugated polymer. It is found that CBS can significantly reduce chain rigidity, melting point, as well as glass transition temperature, and further examined the influence of CBS on the crystallization behaviors of PNDI-C3 to C6, including isothermal crystallization kinetics, crystal polymorphism, and subsequently time-dependent modulus. The authors conclude that tuning backbone rigidity can be an effective approach to adjust the mechanical properties of polymers for flexible electronics. Risko et al. perform large-scale atomistic molecular dynamics simulations to examine the length effect of CBS incorporated into the DPP polymer backbone on the polymer structure, dynamics, and thermal properties. They discover that longer alkyl segments lead to polymer chains that are more flexible, compact, and mobile, with lower glass transition temperatures for the condensed phase.

Applications of semiconducting polymers have been broadly covered. Andrew et al. provide their perspectives on sustainable polymer materials for flexible light control and thermal management. The authors also shed light on the advantages and disadvantages of semiconducting polymers compared to other nanomaterials. Garments functionalized with semiconducting polymers may significantly reduce indoor heating and cooling costs, contributing to energy-saving and temperature-regulating technologies to combat global energy and climate crisis. Chen and Ercan et al. shared their latest research development of photonic field-effect transistor (FET) memory devices using poly(9,9-dioctylfluorene) (PFO)-block-poly (vinylphenyl oxadiazole) (POXD) conjugated block copolymers. By optimizing the POXD content in the block copolymer, a memory ratio (ION/IOFF) of ~105 was achieved after 104 s, indicating its superior long-term stability and data discernibility. This electret in photonic transistor memory devices opens up the possibility of developing photonic memory, human perception, and futuristic communication systems. Di et al. systematically review the development of implantable electronic sensors based on polymer materials. They also surveyed the strategies to integrate polymers with implantable sensors, encompassing device interface, geometry, and integration. A deep understanding of the role of polymers in implantable sensors paves the way to safe, multifunctional, and multi-sized electronic devices with long-term stability and ultrasensitivity for in vivo sensing. With these implantable sensors developed, accurate and dynamical monitor of health status can further assist doctors with customized healthcare recommendations in the future. Zhao and Liu et al. summarize the recent progress in polymer-based organic circuits, ranging from digital circuits like logic gates, to analog circuits like amplifiers. The authors point out a few hurdles to overcome before organic circuits become a reality. These include the lack of a precise and universal charge transport model covering a wide variety of organic semiconductors that makes it difficult for circuit designers to simulate device and circuit behaviors, the lack of reproducibility, as well as batch-to-batch variation in devices.

In recent years, mixed conductor-based organic electrochemical transistors (OECTs) have been under the spotlight and are heavily considered for biosensing and neuromorphic computing.3 Lei et al. analyze the molecular design strategies for high-performance OECT materials and highlight the characteristics and effects of backbone design and side-chain engineering. They discuss some neglected and unsolved issues, such as the lack of high-performance n-type polymers and a standardized method to evaluate polymer performance, while offering their outlook for future OECTs research. Oh et al. provide an overview of semiconducting polymer-based neuromorphic devices and their applications in neuromorphic bioelectronics. They particularly focus on recent advances in semiconducting polymer-based three-terminal artificial synapses that mimic neural communication behaviors. They envision that rapid advancement in semiconducting polymer-based neuromorphic bioelectronics will accelerate the commercialization of human-machine interfacial systems, including intelligent prosthetics and implantable diagnostic devices. Poly(3,4-ethylenedioxythiophene) (PEDOT) is the best-known and studied mixed conductor with favorable properties. It is often applied as the active material in biological sensors, OECTs, neuromorphic bioelectronics, and electrochromic devices. However, PEDOT has several drawbacks, which can limit its effectiveness, or long-term use, including weak adhesion to substrates such as ITO-coated glass, poorly controlled surface morphology, and reduced electrochemical stability over time. Nielsen et al. demonstrate a novel polymer-based on covalently modified EDOT (PEDOT-Crown), featuring polar motifs and a 15-crown-5 moiety. They show that PEDOT-Crown has a wealth of advantageous properties including superior adhesion to ITO under physical and electrochemical duress; a more uniform surface morphology; and electrochemical properties including a higher contrast ratio, red-shifted polaron and bipolaron absorption features, bleaching of the neutral absorption band across a narrower voltage range, and more Faradaic rather than capacitive behavior. This study is a testament that molecular design is an effective strategy to push forward mixed conductors towards real applications, while the results from Graham et al. demonstrate understanding the doping process is equally important in these applications. The authors investigate how counterion structures impact the electrochemical doping ability, oxidation potential, ionization energy, and polaron absorbance of regioregular (rr) and regiorandom (rra) P3HT. It is found that the anions also result in significant differences in polaron absorbance and ionization energies, thereby emphasizing the critical role of the counterion in determining the optical and electronic properties of doped π-conjugated polymers.

Other than polymer thin-film electronics, 3D printed electronics have emerged. Chortos reviews extrusion 3D printing of conjugated polymers for biointerfaces, soft robotics, and energy storage. It summarizes progress in the emerging field of 3D printed semiconducting polymers using three extrusion-printing processes: direct ink write, meniscus-guided printing, and electrohydrodynamic printing. Ink designs for direct in write are described in-depth, including strategies for modifying the rheology and conductivity of the inks.

It is clear that the field of semiconducting polymers has advanced to a new level from reading these reviews and research progress. What is next in semiconducting polymer? First, the community has to address reproducibility, scalability, and sustainability in polymer synthesis. It is highly desired to have controlled polymerization methods in order to minimize side reactions that lead to poor reproducibility. The more steps it takes to prepare a polymer, the less likely it would be commercially adopted. The use of toxic reagents and solvents will also prohibit the adoption of the materials and devices. Sustainability has to be considered in the stage of molecular design. Second, the community must develop controlled thin film formation and patterning processes. Roll-to-roll manufacturing is one of the biggest features for polymer-based flexible electronics, which significantly brings down the cost. However, uniform coating over a large area presents a significant challenge. It requires a deep understanding of polymer aggregations in solutions, fluid dynamics, and drying kinetics. Third, the community has to develop a theoretical model to precisely describe charge transport behaviors of polymer thin films, which is a prerequisite condition for circuit design. Fourth, a better understanding of polymer degradation and device failure modes is of necessity. Such studies are currently not available but are essential for the technological development of flexible electronics. Last but not least, it requires multidisciplinary efforts to bring semiconducting polymers and polymer electronics to the market.