Evidence of Preformed Lewis Acid–Base and Wheland-Type Complexes Acting as Dopants for p-Type Conjugated Polymers
Evidence of Preformed Lewis Acid–Base and Wheland-Type Complexes Acting as Dopants for p-Type Conjugated Polymers
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DOI：
10.1021/acsapm.1c01906
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发表时间：
2022-02
影响因子：
5
通讯作者：
T. Mukhopadhyaya;Taein Lee;Connor Ganley;P. Clancy;H. Katz
中科院分区：
文献类型：
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作者：
T. Mukhopadhyaya;Taein Lee;Connor Ganley;P. Clancy;H. Katz
聚合物半导体的高效掺杂是其作为导体发展的必要条件。虽然路易斯酸如B(C6F5)3已显示出作为聚合物掺杂剂的前景，但其掺杂机理尚不完全清楚。我们建立了B(C6F5)3的1:1两性离子（包括“惠兰型”）配合物与共轭分子二氟双（三乙基硅乙基）噻吩（diF-TES-ADT）和二十二烷基噻吩（DTT-12），并通过1h NMR，紫外-可见光谱，EPR光谱，光学和扫描电子显微镜能量色散x射线能谱（SEM-EDS）和x射线衍射进行了表征。我们将这些配合物作为三种共轭聚合物的p掺杂剂，并通过电导率测量、塞贝克研究、场效应晶体管（FET）和远程栅极传感（RG-FET）测量确定了它们的掺杂能力。电导率的变化依赖于共轭分子加合物成分，与加合物本身作为氧化剂的作用一致。加合物能引起纺丝聚合物薄膜表面电位的变化，其行为与常规掺杂物相似。通过栅极遥感计算载流子密度，发现这些加合物可以产生空穴。我们还研究了先加入B(C6F5)3，再加入整齐共轭分子的效果；观察到的行为与使用预成型加合物不同，这与加合物在兴奋剂期间保持完整一致。当在聚合物中加入B(C6F5)3，然后加入未络合的共轭分子时，产生的空穴载流子密度低于B(C6F5)3掺杂产生的空穴载流子密度，但往往大于Wheland配合物产生的空穴载流子密度，表明在这种情况下形成加合物的可能性很大。密度泛函理论计算表明，硼烷与共轭分子和聚合物段之间的加合物形成在能量上是有利的，如果考虑库仑效应和熵效应，加合物与中性聚合物之间的电荷转移是可能的。因此，这些加合物可以被认为是共轭聚合物的可能掺杂位点。
Efficient doping of polymer semiconductors is essential for their development as conductors. Although Lewis acids such as B(C6F5)3have shown promise as dopants for polymers, their doping mechanism is not fully understood. We created 1:1 zwitterionic (including “Wheland-type”) complexes of B(C6F5)3with conjugated molecules difluorobis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT) and didodecylthienothiophene (DTT-12) and characterized them with1H NMR, UV–vis spectroscopy, EPR spectroscopy, optical and scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS), and X-ray diffraction. We employed these complexes as p-dopants for three conjugated polymers and established their doping abilities by conductivity measurements, Seebeck studies, field effect transistor (FET), and remote-gate sensing (RG-FET) measurements. Conductivity changes were dependent on the conjugated molecule adduct component, consistent with the adduct itself serving as the oxidant. The adduct complexes were capable of inducing changes in the surface potential of spun polymer films similar to the behavior shown by conventional dopants. Charge carrier density calculations by remote gate sensing revealed that these adducts can generate holes. We also studied the effect of adding the B(C6F5)3first, followed by addition of the neat conjugated molecules; the observation of behavior that was different from that using preformed adducts was consistent with the adducts remaining intact during doping. When B(C6F5)3was added to the polymers, followed by uncomplexed conjugated molecules, the generated hole carrier density is lower than that generated by the B(C6F5)3dopant but often greater than that generated by the Wheland complexes, indicating a high probability of adduct formation in this case. Density functional theory calculations show that adduct formation between boranes and the conjugated molecules and segments of the polymers is energetically favorable and that some charge transfer between adducts and neutral polymers is plausible if Coulombic and entropic effects are taken into consideration. Thus, such adducts can be considered as possible doping sites for conjugated polymers.