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Effect Of Substrate Heating And Electrodes Modification On The Performance Of Organic Field Effect Transistors

Posted on:2016-08-19Degree:MasterType:Thesis
Country:ChinaCandidate:L C ZhengFull Text:PDF
GTID:2308330461983557Subject:Optics
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Organic field-effect transistors(OFETs) have received wide attention since their birth. Their great potential applications in electronic devices are derived from advantages in simple preparation process, low cost, suitable for large area low temperature fabrication, compatible with flexible substrates and so on. They have been applied in RF cards, sensors, electronic papers, RFID tags and also provided new solutions for large-scale integrated circuit and large flat panel display. Therefore, OFETs have been one of the important research fields in organic electronics.Both carrier transport and injection in OFETs are crucial to device performance as they are injection type devices. On the one hand, it’s a effective way to improve thin film morphology by heating substrate in active layer evaporation process, by which optimization of the carrier transport will be achieved in this way. On the other side, inserting modification materials between electrodes and active layer can improve the carrier injection effectively. In view of these two aspects, the substrate heating and the electrodes modification in the OFET devices based on different n-type or p-type semiconductors was adopted to investigate the influences of the different substrate temperature and electrodes modification on the performance of OFET devices in this work. The specific research contents are as follows:(1) We fabricated bottom-gate top-contact OFET devices with pentacene as active layer and PMMA as insulator. The substrate temperature were kept at 15, 30, 60, 90?C respectively during the evaporation process of pentacene thin film. This result shows that the devices at the substrate temperature of 60?C exhibited the relatively best performance. The effective mobility rised from 2.9×10-4 cm2/V·s at 15?C to 3.39×10-3cm2/V·s. By means of theoretical analysis, we presented the cause of the optimal performance of the OFETs at the substrate temperature of 60?C.(2) Base on the optimum substrate temperature, the bottom-gate top-contact OFETs with pentacene as active layer and PMMA as insulator were fabricated and transition metal oxide Mo O3 was inserted between Al electrodes and pentacene layer. Compared with the devices without Mo O3 modification, the effective mobility improved to 2.25×10-1cm2/V·s which was increased by 66 times. And the threshold voltage was decreased from 12 V to 3V. This result can be ascribed to the introduction of Mo O3 layer, which can decrease the injection barrier between Al electrodes and pentacene effectively, and reduce the contact resistance, then improve the carrier injection.(3) We explored and fabricated the OFET devices based on n-type semiconductor material P13, and employed the cathode injection enhancement materials such as Cs2CO3 and Cs CH2 COOH as the electrode-modified materials. The influence of these two materials on the performance of P13-OFETs were investigated. The P13 based devices without electrodes modification exhibited typical n-type output characteristics. The performance of devices with Cs2CO3 buffer layer were slightly increased. While the devices with Cs CH2 COOH modified electrodes failed to get stable performance. Based on these experimental results, we analyzed the possible causes.
Keywords/Search Tags:Organic field-effect transistors, carrier transport and injection, substrate heating, electrodes modification
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