凭借其低电压、高跨导、良好的生物相容性和机械柔韧性等独特优势，有机电化学晶体管（OECTs）在生物传感、逻辑电路和神经形态计算等方面展现出巨大的应用潜力。近年来，给体-受体（D-A）共聚物因可调节的能级、长期运行稳定等优势受到了研究者的广泛关注，成为一类新兴的高效p型OECTs材料。然而，此类D-A型材料因其构筑单元结构复杂、制备成本较高和相应器件性能滞后等问题限制了其OECTs的进一步发展。为此，本论文设计合成了一类基于苯并噻二唑单元的结构简单、易合成的高效p型D-A共聚物，并采用热退火及分子量调控的优化策略，系统研究了分子结构、薄膜微观形貌、器件性能及其稳定性的构效关系。本论文主要研究内容如下：

    （1）设计合成了以苯并噻二唑为构建单元的烷氧侧链基受体模块，分别得到骨架为弧型和线型的低成本D-A共聚物PTBT-P和PTTBT-P。研究表明，线型PTTBT-P薄膜展现出长程有序的结晶特性和紧密的层间堆积，有利于获得高效的离子掺杂和电荷传输。基于线型PTTBT-P 的OECT器件，获得了理想的体积电容139.99 F cm^-3以及高空穴迁移率2.44 cm² V ^-1 s ^-1，实现优异的μC*值342 F cm^-1 V^-1 s^-1。相比之下，弧型PTBT-P薄膜由于部分无序和短程结晶特性使其μC*值仅为45 F cm^-1 V^-1 s^-1。此外，基于线型PTTBT-P的OECT器件在“打开”和“关闭”状态之间切换工作4800秒后，器件可维持90%的高电流值，呈现出良好的长期工作稳定性。更为重要的是，本章节提出采用工业价值指数来评估当前OECTs的商业化性价比潜力，结果证明了线型PTTBT-P材料具有较高的性价比优势。

    （2）为精细调控PTBT-P和PTTBT-P铸态薄膜的微观形貌结构，本章节采用热退火调控策略并系统研究退火温度对薄膜形貌和离子掺杂能力的影响。研究表明，热退火限域的薄膜结晶特性使基于PTBT-P的OECT器件迁移率从铸态薄膜的0.09 cm ² V^-1 s^-1小幅度提升至0.35 cm ² V^-1 s^-1；而退火优化后的PTTBT-P薄膜呈现出高度结晶有序性和理想的离子掺杂能力，相对于铸态薄膜其迁移率提升了近6倍，高达2.44 cm ² V^-1 s^-1，并且保持良好的体积电容（C*=139.99 F cm^-3）。最终，在热退火的优化调控下，基于PTTBT-P的OECT器件性能实现了μC*从63 F cm^-1 V^-1 s^-1至342 F cm^-1 V^-1 s^-1的提升。本章节研究证明了热退火策略在调控薄膜微观结构及提升OECTs器件性能中的潜力。

    （3）本章研究聚焦基于D-A共聚物的OECT器件工作稳定性，从材料分子量调控到器件稳定性的联动角度出发，系统研究了分子结构、薄膜微观形貌、器件性能及其稳定性的构效关系。通过控制聚合反应时间，成功合成出三种不同分子量的PTTBT-P共聚物。研究表明，分子量的提升促进PTTBT-P薄膜分子聚集行为同时伴随着薄膜结晶有序度的增加，有利构筑了更稳固的薄膜微观形貌。电化学光谱及OECT器件稳定性测试证明了高分子量PTTBT-P实现高的器件长期工作稳定性（T_98%=1600 s）。研究工作证明了D-A共聚物分子量调控的策略有效提升了OECT的电荷传输性能和薄膜结构的稳固性，为后期设计高效长期稳定的OECT材料提供了指导。

  Due to the unique advantages of low voltage, high transconductance, good biocompatibility, and mechanical flexibility, organic electrochemical transistors (OECTs) possess great potential for applications in biosensing, logic circuits, and neuromorphic computing. In recent years, donor-acceptor (D-A) copolymers have received a lot of attention from researchers for their adjustable energy levels, and long-term operational stability have become an emerging class of highly efficient p-type OECTs materials. However, those D-A copolymers have still limited the further development of their OECTs due to their complex building block structure, high preparation cost, and low performance of the corresponding devices. To this end, a class of highly efficient p-type D-A copolymers based on benzothiadiazole units with simple structures and easy synthesis was designed and synthesized in this thesis, and the conformational relationships of molecular structures, film microscopic morphology, device performance, and their stability were systematically investigated using the optimization strategies of thermal annealing and molecular weight modulation. The main research contents are as follows:

  (1) The alkoxy side chain-based acceptor modules with benzothiadiazole as the building block was designed and synthesized to obtain low-cost D-A copolymers PTBT-P and PTTBT-P with arc-shaped and linear skeletons, respectively. The results show that the linear PTTBT-P films show long-ranged crystalline ordering and tight molecular stacking, which are beneficial to obtain efficient ion doping and charge transport. The OECT devices based on linear PTTBT-P obtained an ideal capacitance of 139.99 F cm^-3 and a high hole mobility of 2.44 cm² V^-1 s^-1, achieving an excellent μC* value of 342 F cm^-1 V^-1 s^-1. In contrast, PTBT-P-based OECT shows the undesired μC* value of only 45 F cm^-1 V^-1 s^-1, probably due to the partial disorder and short-ranged crystallization. In addition, the OECT device based on linear PTTBT-P can maintain a 90% high current value after 4800s of switching between the "on" and "off " states, showing good long-term stability. More importantly, this chapter proposes an industrial value index (FOM) to evaluate the commercialized potential of the current OECTs. The results show that linear PTTBT-P among the reported D-A type copolymers have the highest cost-effective feature.

  (2) To finely regulate the microstructure of the as-cast PTBT-P and PTTBT-P thin films, this Chapter adopts a thermal annealing control strategy and systematically investigates the effects of annealing temperature on the morphology and ion doping ability of the films. The results show that the limited film crystalline evolution upon thermal treatment slightly increases the mobility of PTBT-P-based OECT devices from 0.09 cm² V^-1 s^-1 to 0.35 cm² V^-1 s^-1. However, the annealed PTTBT-P film showed much-improved crystalline ordering and ideal ion doping ability. Compared with the as-cast PTTBT-P film, the mobility was significantly increased by nearly 6 times to 2.44 cm² V^-1 s^-1, and good volume capacitance (C*=139.99 F cm^-3) was maintained. Finally, the performance of PTTBT-P-based OECTs can be improved from 63 F cm^-1 V^-1 s^-1 to 342 F cm^-1 V^-1 s^-1 under optimal thermal annealing. The present study demonstrates the potential of thermal annealing strategies in regulating the microstructure of thin films to improve the performance of OECTs devices.

  (3) This chapter focuses on the operating stability of OECT devices based on D-A copolymer and systematically investigates the constitutive relationships among molecular structure, film micromorphology, device performance, and its stability from the perspective of the linkage of material molecular weight regulation to device stabilization type. By controlling the polymerization time, three different molecular weights were successfully synthesized for PTTBT-P copolymers.With the increase in molecular weight, the molecular aggregation behavior of PTTBT-P films along with the increase in the crystalline order of the films, favors the construction of a more solid film micromorphology. Electrochemical spectroscopy and OECT device stability measurement demonstrated that the high molecular weight of PTTBT-P achieves high long-term operating devices stability (T_98% up to 1600s). The research work demonstrated that the strategy of molecular weight regulation of D-A copolymer effectively improves the charge transport and the robustness of the film microstructure, which guides the further design of efficient and long-term stable OECT materials.

[1] 付银鹏，王红旺，王靖宵，王磊，菅傲群，张文栋，冀健龙. 双极电化学法制备有机电化学晶体管阵列 [J]. 半导体器件, 2020, 45: 524-529.

[2] 冯晓倩，顾文，张霞，蒋浩. 基于有机薄膜晶体管与有机电化学晶体管的生物传感器研究进展 [J]. 材料导报, 2019, 33: 1243-1250.

[3] P Andersson Ersman, R Lassnig, J Strandberg, et al. All-printed large-scale integrated circuits based on organic electrochemical transistors [J]. Nat. Commun., 2019, 10(1): 5053.

[4] K Manoli, M Magliulo, M Y Mulla, et al. Printable Bioelectronics To Investigate Functional Biological Interfaces [J]. Angew. Chem. Int. Ed. , 2015, 54(43): 12562-12576.

[5] J Xiang, Y Li, Q Li, et al. Electrically tunable selective reflection of light from ultraviolet to visible and infrared by heliconical cholesterics [J]. Adv. Mater., 2015, 27(19): 3014-3018.

[6] A M Pappa, O Parlak, G Scheiblin, et al. Organic Electronics for Point-of-Care Metabolite Monitoring [J]. Trends Biotechnol., 2018, 36(1): 45-59.

[7] D T Simon, E O Gabrielsson, K Tybrandt, et al. Organic Bioelectronics: Bridging the Signaling Gap between Biology and Technology [J]. Chem. Rev., 2016, 116(21): 13009-13041.

[8] N A Kukhta, A Marks, C K Luscombe. Molecular Design Strategies toward Improvement of Charge Injection and Ionic Conduction in Organic Mixed Ionic-Electronic Conductors for Organic Electrochemical Transistors [J]. Chem. Rev., 2022, 122(4): 4325-4355.

[9] A M Pappa, D Ohayon, A Giovannitti, et al. Direct metabolite detection with an n-type accumulation mode organic electrochemical transistor [J]. Sci. Adv., 2018, 4(6): eaat0911.

[10] H S White, G P Kittlesen, M S Wrighton. Chemical derivatization of an array of three gold microelectrodes with polypyrrole: fabrication of a molecule-based transistor [J]. J. Am. Chem. Soc., 1984, 106(18): 5375-5377.

[11] X Strakosas, M Bongo, R M Owens. The organic electrochemical transistor for biological applications [J]. J. Appl. Poly. Sci., 2015, 132(15): 41735.

[12] J Rivnay, S Inal, A Salleo, et al. Organic electrochemical transistors [J]. Nat. Rev. Mater., 2018, 3(2): 17086.

[13] D A Bernards, G G Malliaras. Steady-State and Transient Behavior of Organic Electrochemical Transistors [J]. Adv. Funct. Mater., 2007, 17(17): 3538-3544.

[14] S Inal, G G Malliaras, J Rivnay. Benchmarking organic mixed conductors for transistors [J]. Nat. Commun., 2017, 8(1): 1767.

[15] R. K. Hallani, B. D. Paulsen, R S A. J. Petty II, M. Moser, , et al. Regiochemistry-Driven Organic Electrochemical Transistor Performance Enhancement in Ethylene Glycol-Functionalized Polythiophenes [J]. J. Am. Chem. Soc., 2021, 143(29): 11007-11018.

[16] D Jeong, I Y Jo, S Lee, et al. High‐Performancen n‐Type Organic Electrochemical Transistors Enabled by Aqueous Solution Processing of Amphiphilicity‐Driven Polymer Assembly [J]. Adv. Funct. Mater., 2022, 32: 2111950.

[17] C B Nielsen, A Giovannitti, D T Sbircea, et al. Molecular Design of Semiconducting Polymers for High-Performance Organic Electrochemical Transistors [J]. J. Am. Chem. Soc., 2016, 138(32): 10252-10259.

[18] A Giovannitti, K J Thorley, C B Nielsen, et al. Redox-Stability of Alkoxy-BDT Copolymers and their Use for Organic Bioelectronic Devices [J]. Adv. Funct. Mater., 2018, 28(17): 1706325.

[19] A Giovannitti, D T Sbircea, S Inal, et al. Controlling the mode of operation of organic transistors through side-chain engineering [J]. Proc. Natl. Acad. Sci., 2016, 113(43): 12017-12022.

[20] A Savva, R Hallani, C Cendra, et al. Balancing Ionic and Electronic Conduction for High‐Performance Organic Electrochemical Transistors [J]. Adv. Funct. Mater., 2020, 30(11): 1907657.

[21] M Moser, Y Wang, T C Hidalgo, et al. Propylene and butylene glycol: new alternatives to ethylene glycol in conjugated polymers for bioelectronic applications [J]. Mater. Horiz., 2022, 9(3): 973-980.

[22] M Moser, T C Hidalgo, J Surgailis, et al. Side Chain Redistribution as a Strategy to Boost Organic Electrochemical Transistor Performance and Stability [J]. Adv. Mater., 2020, 32(37): 2002748.

[23] A L Jones, M De Keersmaecker, L R Savagian, et al. Branched Oligo(ether) Side Chains: A Path to Enhanced Processability and Elevated Conductivity for Polymeric Semiconductors [J]. Adv. Funct. Mater., 2021, 31(35): 2102688.

[24] B T DiTullio, L R Savagian, O Bardagot, et al. Effects of Side-Chain Length and Functionality on Polar Poly(dioxythiophene)s for Saline-Based Organic Electrochemical Transistors [J]. J. Am. Chem. Soc., 2023, 145(1): 122-134.

[25] Z Li, S-W Tsang, X Du, et al. Alternating Copolymers of Cyclopenta[2,1-b;3,4-b′]dithiophene and Thieno[3,4-c]pyrrole-4,6-dione for High-Performance Polymer Solar Cells [J]. Adv. Funct. Mater., 2011, 21(17): 3331-3336.

[26] S Van Mierloo, A Hadipour, M-J Spijkman, et al. Improved Photovoltaic Performance of a Semicrystalline Narrow Bandgap Copolymer Based on 4H-Cyclopenta[2,1-b:3,4-b′]dithiophene Donor and Thiazolo[5,4-d]thiazole Acceptor Units [J]. Chem. Mater., 2012, 24(3): 587-593.

[27] H N Tsao, D M Cho, I Park, et al. Ultrahigh mobility in polymer field-effect transistors by design [J]. J. Am. Chem. Soc., 2011, 133(8): 2605-2612.

[28] L Lan, J Chen, Y Wang, et al. Facilely Accessible Porous Conjugated Polymers toward High-Performance and Flexible Organic Electrochemical Transistors [J]. Chem. Mater., 2022, 34(4): 1666-1676.

[29] Y Wang, E Zeglio, H Liao, et al. Hybrid Alkyl-Ethylene Glycol Side Chains Enhance Substrate Adhesion and Operational Stability in Accumulation Mode Organic Electrochemical Transistors [J]. Chem. Mater., 2019, 31(23): 9797-9806.

[30] A Giovannitti, R B Rashid, Q Thiburce, et al. Energetic Control of Redox-Active Polymers toward Safe Organic Bioelectronic Materials [J]. Adv. Mater., 2020, 32(16): 1908047.

[31] A Giovannitti, I P Maria, D Hanifi, et al. The Role of the Side Chain on the Performance of N-type Conjugated Polymers in Aqueous Electrolytes [J]. Chem. Mater., 2018, 30(9): 2945-2953.

[32] A Giovannitti, C B Nielsen, D T Sbircea, et al. N-type organic electrochemical transistors with stability in water [J]. Nat. Commun., 2016, 7: 13066.

[33] I P Maria, B D Paulsen, A Savva, et al. The Effect of Alkyl Spacers on the Mixed Ionic‐Electronic Conduction Properties of N‐Type Polymers [J]. Adv. Funct. Mater., 2021, 31(14): 2008718.

[34] B Ding, G Kim, Y Kim, et al. Influence of Backbone Curvature on the Organic Electrochemical Transistor Performance of Glycolated Donor-Acceptor Conjugated Polymers [J]. Angew. Chem. Int. Ed., 2021, 60(36): 19679-19684.

[35] X Luo, H Shen, K Perera, et al. Designing Donor-Acceptor Copolymers for Stable and High-Performance Organic Electrochemical Transistors [J]. ACS Macro. Lett., 2021, 10(8): 1061-1067.

[36] M Moser, A Savva, K Thorley, et al. Polaron Delocalization in Donor-Acceptor Polymers and its Impact on Organic Electrochemical Transistor Performance [J]. Angew. Chem. Int. Ed., 2021, 60(14): 7777-7785.

[37] Y Wang, E Zeglio, L Wang, et al. Green Synthesis of Lactone‐Based Conjugated Polymers for n‐Type Organic Electrochemical Transistors [J]. Adv. Funct. Mater., 2022, 32(16): 2111439.

[38] D Khodagholy, T Doublet, P Quilichini, et al. In vivo recordings of brain activity using organic transistors [J]. Nat. Commun., 2013, 4: 1575.

[39] S E Chen, L Q Flagg, J W Onorato, et al. Impact of varying side chain structure on organic electrochemical transistor performance: a series of oligoethylene glycol-substituted polythiophenes [J]. J. Mater. Chem. A, 2022, 10: 10738-10749.

[40] L Huang, Z Wang, J Chen, et al. Porous Semiconducting Polymers Enable High-Performance Electrochemical Transistors [J]. Adv. Mater., 2021, 33(14): 2007041.

[41] E Tan, J Kim, K Stewart, et al. The Role of Long-Alkyl-Group Spacers in Glycolated Copolymers for High-Performance Organic Electrochemical Transistors [J]. Adv. Mater., 2022, 34(27): e2202574.

[42] T Lei, Y Cao, X Zhou, et al. Systematic Investigation of Isoindigo-Based Polymeric Field-Effect Transistors: Design Strategy and Impact of Polymer Symmetry and Backbone Curvature [J]. Chem. Mater., 2012, 24(10): 1762-1770.

[43] R Rieger, D Beckmann, A Mavrinskiy, et al. Backbone Curvature in Polythiophenes [J]. Chem. Mater., 2010, 22(18): 5314-5318.

[44] S Shinamura, I Osaka, E Miyazaki, et al. Linear- and angular-shaped naphthodithiophenes: selective synthesis, properties, and application to organic field-effect transistors [J]. J. Am. Chem. Soc., 2011, 133(13): 5024-5035.

[45] W Yang, W Wang, Y Wang, et al. Balancing the efficiency, stability, and cost potential for organic solar cells via a new figure of merit [J]. Joule, 2021, 5(5): 1209-1230.

[46] W Lee, G-H Kim, S-J Ko, et al. Semicrystalline D-A Copolymers with Different Chain Curvature for Applications in Polymer Optoelectronic Devices [J]. Macromolecules, 2014, 47(5): 1604-1612.

[47] Y Li, H Fu, Z Wu, et al. Regulating the Aggregation of Unfused Non-Fullerene Acceptors via Molecular Engineering towards Efficient Polymer Solar Cells [J]. ChemSusChem, 2021, 14(17): 3579-3589.

[48] F C Spano. The spectral signatures of Frenkel polarons in H- and J-aggregates [J]. Acc. chem. res., 2010, 43(3): 429-439.

[49] Q Zhao, J Liu, H Wang, et al. Balancing the H- and J-aggregation in DTS(PTTh2)2/PC70BM to yield a high photovoltaic efficiency [J]. J. Mater. Chem. C, 2015, 3(31): 8183-8192.

[50] S Sweetnam, K R Graham, G O Ngongang Ndjawa, et al. Characterization of the polymer energy landscape in polymer:fullerene bulk heterojunctions with pure and mixed phases [J]. J. Am. Chem. Soc., 2014, 136(40): 14078-114088.

[51] B Kang, Z Wu, M J Kim, et al. Aqueous-Alcohol-Processable High-Mobility Semiconducting Copolymers with Engineered Oligo(ethylene glycol) Side Chains [J]. Chem. Mater., 2019, 32(3): 1111-1119.

[52] Y Li, M Wang, Q Zhang, et al. Fine-tuned crystallinity of polymerized non-fullerene acceptor via molecular engineering towards efficient all-polymer solar cell [J]. Chem. Eng. J., 2021, 428: 131232.

[53] R Giridharagopal, L Q Flagg, J S Harrison, et al. Electrochemical strain microscopy probes morphology-induced variations in ion uptake and performance in organic electrochemical transistors [J]. Nat. Mater., 2017, 16(7): 737-742.

[54] Y Li, W Zhou, Y Li, et al. Unravelling Atomic Structure and Degradation Mechanisms of Organic-Inorganic Halide Perovskites by Cryo-EM [J]. Joule, 2019, 3(11): 2854-2866.

[55] L Q Flagg, C G Bischak, J W Onorato, et al. Polymer Crystallinity Controls Water Uptake in Glycol Side-Chain Polymer Organic Electrochemical Transistors [J]. J. Am. Chem. Soc., 2019, 141(10): 4345-4354.

[56] W Y Yang, W Wang, Y H Wang, et al. Balancing the efficiency, stability, and cost potential for organic solar cells via a new figure of merit [J]. Joule, 2021, 5(5): 1209-1230.

[57] X Shang, Y Yin, S Chen, et al. Unravelling the Correlation between Microphase Separation and Cocrystallization in Thiophene-Selenophene Block Copolymers for Organic Field-Effect Transistors [J]. Macromolecules, 2020, 53(22): 10245-10255.