有机薄膜晶体管的制备及其气敏性能的研究

发布时间：2018-04-30 11:45

本文选题：有机薄膜晶体管 + 气体传感器　；参考：《电子科技大学》2016年博士论文

【摘要】：有机薄膜晶体管(Organic Thin film transistor,OTFT)由于其制备成本低、易实现大面积、制备方法简单和可弯折等特点在未来具有广阔的应用前景。目前,OTFT器件在有机发光二极管显示、射频识别、传感器等领域显示了重要的应用价值。尤其是在气体传感器方面,多参数模式、易集成和可弯折等优点成为其他类型气体传感器所不能取代的优势。OTFT气体传感器最大的特点在于有源层薄膜是OTFT器件的导电沟道层也是气体传感器的气体敏感薄膜。因此。针对OTFT有源层薄膜的选择、修饰、改性一直是人们提高OTFT气体传感器性能所关注的焦点。根据不同类型的OTFT器件的特点,本文采用底栅底接触结构的OTFT器件,以便气体敏感薄膜能够与待测气体分子直接接触,提高OTFT气体传感器的性能。制备了以聚(三-己基噻吩)(Poly(3-hexylthiophene),P3HT)、P3HT-氧化锌(Zinc Oxide,ZnO)纳米棒的复合薄膜、P3HT/还原的氧化石墨烯(Reduced Graphene Oxide,RGO)分层薄膜等作为敏感薄膜的OTFT气体传感器,对其器件的基本电学性能和气敏性能进行了系统的分析和研究。同时,结合多种分析手段对气敏薄膜的特性进行表征,深入地探讨了气体传感器的气敏机理。论文的主要研究内容包括以下几个方面:1.制备了基于P3HT薄膜的OTFT气体传感器用于检测二氧化氮(nitrogen dioxide,NO2)。研究了气体传感器的敏感机理,得到了气敏薄膜的最佳优化参数。实验结果表明适当的减小器件中敏感薄膜的厚度有利于传感器性能的提高。敏感薄膜采用喷涂成膜的方式制备,通过控制喷涂溶液的体积沉积不同厚度的敏感薄膜。首先,针对P3HT薄膜研究了其对NO2的气体敏感机理。由于栅极电压能够调控器件中载流子的分布状态,对栅极施加不同的电压条件,验证气体传感器的主要响应机制为类似“掺杂效应”。然后,改变敏感薄膜厚度优化OTFT气体传感器的性能。对比不同厚度薄膜器件之间的差异发现:(1)薄膜的厚度增加导致界面处的表面势变大,这样就会在相同的栅极电压下吸附更多的空穴载流子形成导电通道,因此OTFT的阈值电压会向正值方向移动,迁移率增大。(2)随着敏感薄膜厚度的减小,传感器对相同浓度NO2的响应值会变大。这是因为在厚度较小的薄膜中,空气/P3HT界面与P3HT/SiO2界面相邻较近,表面吸附的气体分子会以相对更大程度地扰乱沟道中的空穴载流子传输。2.将Zn O纳米棒掺杂引入到P3HT薄膜中用来优化OTFT气体传感器的性能,并结合对传感器敏感机理的研究,提出了两种快速、准确评估OTFT气体传感器性能的方法,用来解决传感器恢复时间过长造成的响应偏差。文中详细地研究了zno纳米棒的掺杂对p3ht薄膜的微观结构的影响。zno纳米棒促进了p3ht薄膜的结晶度增加和p3ht侧链的取向更加规则,这就会引起器件内载流子运输状态的变化,优化了器件的电学性能。此外,p3ht与zno纳米棒构成了异质结结构导致薄膜中电子与空穴的分布产生变化,改善了器件的性能。室温下测试otft器件对no2的气敏性能,结果表明:otft气体传感器对no2十分敏感,最低检测限达到几ppb。但是在测试高浓度的no2时,存在传感器恢复时间过长的这一问题,影响otft气体传感器的准确性。为了克服这个问题,提出了两种能够快速、准确地评估传感器性能的方法。第一种方法是采用otft器件的阈值电压变化作为传感器的输出信号。多次针对没有完全恢复的器件测试发现在同一浓度的待测气体下,传感器阈值电压的变化基本相同。第二种方法是基于气体分子的吸附行为方程提出的一种数据处理方法。经过试验数据的验证这种方法具有很高的可靠性。3.率先将二硫化钼(molybdenumdisulfide,mos2)引入到聚合物p3ht中作为nh3传感器的敏感材料,制备不同结构的敏感薄膜,发现采用p3ht-mos2复合薄膜的传感器的恢复时间明显缩短。mos2是一种典型的二维半导体材料,其特点是载流子迁移率高。制备的器件由于mos2的存在otft器件的电学性能发生了明显的改变,其中otft的输出特性曲线中的饱和区不再明显。研究了制备的薄膜微观结构的差异发现:mos2的加入使得p3ht分子与分子之间的距离由于相互作用的原因变小了。这就会使载流子在有源层沟道内的传输更为迅速。因此,气体传感器表现出更好的恢复性。而分层膜结构的改善没有复合膜结构的明显。此外,还深入地讨论了气体响应的敏感机理,采用不同载气对传感器的性能进行测试。结果表明:氧气分子在没有进行气体测试之前已经预先占据了强弱的吸附位,当接触到氨气分子之后,氨气分子与氧气分子竞争夺取气体的吸附位。气体的恢复过程是其相反的过程。4.将新型气敏材料rgo与聚合物p3ht制备成p3ht/rgo分层薄膜结构的敏感薄膜,发现rgo作为底层材料可以提高对no2气体的灵敏度,改善rgo薄膜对气体的选择性。文中对制备的器件电学性能测试得到:因为rgo材料的电导率和迁移率都很高,所以otft输出特性曲线没有发现明显的饱和区,这严重地影响了otft的电学性能。但是对于no2气敏性能测试结果得到:采用rgo作为底层,p3ht作为顶层的这种分层薄膜结构明显提高了no2气体传感器的响应和灵敏度。这与rgo本身的二维纳米结构有关,待检测气体分子能够直接与材料的全部原子接触。深入地研究待测气体的实时响应-恢复曲线发现rgo在与no2气体分子吸附时存在着不同的吸附位,响应曲线中存在快慢响应之分。此外,P3HT作为顶层材料对底层RGO材料有一个修饰的作用,阻止了其他气体与底层的RGO接触,提高了基于RGO气体传感器的选择性。
[Abstract]:Organic Thin film transistor (OTFT) has a wide application prospect in the future because of its low preparation cost, easy realization of large area, simple preparation method and bending and so on. At present, OTFT devices have shown important application value in the fields of organic light emitting diode display, radio frequency identification, sensor and so on. As for the gas sensor, the advantages of multi parameter mode, easy integration and bending are the most important features of.OTFT gas sensors which can not be replaced by other types of gas sensors. The active layer film is the conductive channel layer of the OTFT device and the gas sensitive thin film of the gas sensor. Therefore, the choice of the OTFT active layer film is the choice of the active layer film. Modification, modification has always been the focus of people to improve the performance of OTFT gas sensors. According to the characteristics of different types of OTFT devices, this paper uses the OTFT device with the bottom contact structure so that the gas sensitive film can directly contact with the gas molecules to be measured and improve the performance of the OTFT gas sensor. The poly (three - hexyl thiophene) is prepared. Poly (3-hexylthiophene), P3HT), P3HT- Zinc Oxide (Zinc Oxide, ZnO) nanorod composite film, P3HT/ reduced graphene oxide (Reduced Graphene Oxide, RGO) layered film, etc. as sensitive gas sensors, the basic electrical properties and gas sensing properties of the devices are systematically analyzed and studied. The characteristics of gas sensitive film are characterized by means of analysis, and the gas sensing mechanism of gas sensor is deeply discussed. The main contents of this paper are as follows: 1. the OTFT gas sensor based on P3HT film is prepared to detect nitrogen dioxide (nitrogen dioxide, NO2). The sensitive mechanism of gas sensor is studied, and gas is obtained. The optimum parameters of the sensitive thin film are obtained. The experimental results show that the appropriate thickness of the sensitive thin film in the device is beneficial to the performance of the sensor. The sensitive thin film is prepared by spraying film, and the sensitive film of different thickness is deposited by controlling the volume of the spray solution. First, the needle is studied for the gas sensitivity of the P3HT film to the NO2. The mechanism. Because the grid voltage can regulate the distribution of the carrier in the device and apply different voltage conditions to the gate, it is proved that the main response mechanism of the gas sensor is similar to the "doping effect". Then, the performance of the OTFT gas sensor is optimized by changing the thickness of the sensitive film. The difference between the thin film devices with different thickness is found: (1) The increase of the thickness of the film leads to the larger surface potential at the interface, so that more cavity carriers will be adsorbed at the same gate voltage to form a conductive channel. Therefore, the threshold voltage of OTFT will move towards the positive direction and the mobility increases. (2) the response value of the sensor to the same concentration of NO2 will become larger as the thickness of the sensitive film decreases. It is because in the thin films that the air /P3HT interface is adjacent to the P3HT/SiO2 interface, and the adsorbed gas molecules will disrupt the hole carrier in the channel to a relatively large extent.2., and the Zn O nanorod doping is introduced into the P3HT film to optimize the performance of the OTFT sensor and the sensitive mechanism of the sensor is combined with the sensor. Two rapid and accurate methods for evaluating the performance of OTFT gas sensors are proposed to solve the response deviation of the sensor with long recovery time. The effect of the doping of ZnO nanorods on the microstructure of the P3HT thin film is studied in detail. The.Zno nanorods promote the increase of the crystallinity of the P3HT film and the orientation of the P3HT side chain more. With the addition of rules, this will cause the change of carrier transport state in the device and optimize the electrical performance of the device. In addition, P3HT and ZnO nanorods constitute a heterostructure that leads to the change in the distribution of electrons and holes in the film, and improves the performance of the device. At room temperature, the gas sensing performance of the OTFT device to the NO2 is tested. The results show that OTFT gas sensing is used. The device is very sensitive to NO2, and the minimum detection limit reaches a few ppb., but when testing the high concentration of NO2, there is a problem that has a long recovery time of the sensor, which affects the accuracy of the OTFT gas sensor. In order to overcome this problem, two methods that can quickly and accurately evaluate the performance of the sensor are proposed. The first method is to use the OTFT device. The threshold voltage variation is used as the output signal of the sensor. Many times for the device test which is not fully recovered, the change of the threshold voltage of the sensor is basically the same under the same concentration of gas. The second method is a data processing method based on the adsorption behavior equation of gas molecules. This method has a high reliability.3. first to introduce molybdenumdisulfide (MoS2) into the polymer P3HT as a sensitive material for NH3 sensor, and to prepare sensitive thin films with different structures. It is found that the recovery time of the sensor using p3ht-mos2 composite thin film can obviously shorten the.Mos2 is a typical two-dimensional semiconductor material. The characteristic is the high mobility of the carrier. The electrical performance of the OTFT device is obviously changed because of the existence of MoS2. The saturation zone in the output characteristic curve of the OTFT is no longer obvious. The difference of the microstructure of the prepared thin film is studied. It is found that the addition of MoS2 makes the distance between the P3HT molecules and the molecules due to the interaction. This causes the carrier to transmit more rapidly in the active layer channel. Therefore, the gas sensor shows better recovery. The improvement of the layer membrane structure is not obvious in the composite membrane structure. In addition, the sensitive mechanism of the gas response is discussed deeply, and the performance of the sensor is tested with different carrier gas. The results show that the oxygen molecules have pre occupied the strong and weak adsorption sites before the gas test. When the ammonia molecules are exposed to the ammonia molecules, the ammonia molecules compete with the oxygen molecules to capture the adsorption position of the gas. The recovery process of the gas is the reverse process.4. to prepare the new gas sensitive material RGO and the polymer P3HT into p3ht/rgo stratification. The sensitive film of the membrane structure found that RGO as the underlying material could improve the sensitivity of the NO2 gas and improve the selectivity of the RGO film to the gas. In this paper, the electrical properties of the fabricated devices were tested because the conductivity and mobility of the RGO materials were very high, so the OTFT output characteristic curve did not find the obvious saturation area, which was seriously affected. The electrical performance of OTFT was rounded. But the results of NO2 gas sensitivity test were obtained: using RGO as the bottom layer, the layered thin film structure of P3HT as the top layer obviously improved the response and sensitivity of the NO2 gas sensor. This is related to the two-dimensional nanostructure of the RGO itself, and the gas molecules can be directly contacted with all the atoms of the material to be detected. The real-time response recovery curve of the gas to be measured has been deeply studied. It is found that RGO has different adsorption sites when adsorbing NO2 gas molecules, and there is a quick and slow response in the response curve. In addition, P3HT as a top layer material has a modified effect on the underlying RGO material, which prevents other gases from contacting RGO at the bottom and improves the RGO based gas. The selectivity of the body sensor.

【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN321.5

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