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Power Factor of One Molecule Thick Films and Length Dependence.
ACS Central Science ( IF 12.7 ) Pub Date : 2019-12-05 , DOI: 10.1021/acscentsci.9b01042 Sohyun Park 1 , Seohyun Kang 1 , Hyo Jae Yoon 1
ACS Central Science ( IF 12.7 ) Pub Date : 2019-12-05 , DOI: 10.1021/acscentsci.9b01042 Sohyun Park 1 , Seohyun Kang 1 , Hyo Jae Yoon 1
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There is a rapidly increasing interest in organic thin film thermoelectrics. However, the power factor of one molecule thick organic film, the self-assembled monolayer (SAM), has not yet been determined. This study describes the experimental determination of the power factor in SAMs and its length dependence at an atomic level. As a proof-of-concept, SAMs composed of n-alkanethiolates and oligophenylenethiolates of different lengths are focused. These SAMs were electrically and thermoelectrically characterized on an identical junction platform using a liquid metal top-electrode, allowing the straightforward estimation of the power factor of the monolayers. The results show that the power factor of the alkyl SAMs ranged from 2.0 × 10-8 to 8.0 × 10-12 μW m-1 K-2 and exhibited significant negative length dependence, whereas the conductivity and thermopower of the conjugated SAMs are the two opposing factors that balance the power factor upon an increase in molecular length, exhibiting a maximum power factor of 3.6 × 10-8 μW m-1 K-2. Once correction factors about the ratio of effective contact area to geometrical contact area are considered, the values of power factors can be increased by several orders of magnitude. With a newly derived parametric semiempirical model describing the length dependence of the power factor, it is investigated that one molecule thick films thinner than 10 nm composed of thiophene units can yield power factors rivaling those of famed organic thermoelectric materials based on poly(3,4-ethylenedioxythiophene)/polystyrenesulfonate (PEDOT/PSS) and polyaniline/graphene/double-walled carbon nanotube. Furthermore, how the transition of the transport regime from tunneling to hopping as molecules become long affects power factors is examined.
中文翻译：
一分子厚膜的功率因数和长度相关性。
人们对有机薄膜热电材料的兴趣迅速增长。然而，尚未确定一分子厚的有机膜，即自组装单层膜（SAM）的功率因数。这项研究描述了在SAM中功率因数的实验确定及其在原子水平上的长度依赖性。作为概念验证，重点研究了由不同长度的正链烷硫醇盐和低聚苯硫醇盐组成的SAM。这些SAM在相同的结平台上使用液态金属顶部电极进行了电和热电表征，从而可以直接估算单层的功率因数。结果表明，烷基SAM的功率因数在2.0×10-8至8.0×10-12μWm-1 K-2之间，并表现出显着的负长度依赖性，而共轭SAM的电导率和热功率是两个相反的因素，它们随着分子长度的增加而平衡功率因数，最大功率因数为3.6×10-8μWm-1 K-2。一旦考虑了有关有效接触面积与几何接触面积之比的校正系数，功率因数的值就可以增加几个数量级。利用新推导的描述功率因数长度依赖性的参数半经验模型，研究了由噻吩单元组成的，厚度小于10 nm的一分子厚膜可以产生与基于聚（3,4）的著名有机热电材料相媲美的功率因数。 -乙撑二氧噻吩）/聚苯乙烯磺酸盐（PEDOT / PSS）和聚苯胺/石墨烯/双壁碳纳米管。此外，
更新日期：2019-12-27
中文翻译：
一分子厚膜的功率因数和长度相关性。
人们对有机薄膜热电材料的兴趣迅速增长。然而，尚未确定一分子厚的有机膜，即自组装单层膜（SAM）的功率因数。这项研究描述了在SAM中功率因数的实验确定及其在原子水平上的长度依赖性。作为概念验证，重点研究了由不同长度的正链烷硫醇盐和低聚苯硫醇盐组成的SAM。这些SAM在相同的结平台上使用液态金属顶部电极进行了电和热电表征，从而可以直接估算单层的功率因数。结果表明，烷基SAM的功率因数在2.0×10-8至8.0×10-12μWm-1 K-2之间，并表现出显着的负长度依赖性，而共轭SAM的电导率和热功率是两个相反的因素，它们随着分子长度的增加而平衡功率因数，最大功率因数为3.6×10-8μWm-1 K-2。一旦考虑了有关有效接触面积与几何接触面积之比的校正系数，功率因数的值就可以增加几个数量级。利用新推导的描述功率因数长度依赖性的参数半经验模型，研究了由噻吩单元组成的，厚度小于10 nm的一分子厚膜可以产生与基于聚（3,4）的著名有机热电材料相媲美的功率因数。 -乙撑二氧噻吩）/聚苯乙烯磺酸盐（PEDOT / PSS）和聚苯胺/石墨烯/双壁碳纳米管。此外，
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