| Image sensors are widely used in various fields.With the emergence of new applications in the medical,security,automotive and military fields,research has begun to focus on reducing the cost of sensor fabrication,making sensors smarter,and achieving flexible large-area image sensing for different scenarios.In this paper,metal oxide thin film transistor(MO TFT)is used as the control tube of the sensor array and organic photodiode(OPD)is used as the photoelectric device to prepare the image sensor,because MO TFT has advantages of low leakage current,high mobility and flexible large area preparation,while OPD has the advantages of simple preparation process,low cost,large area preparation and selective absorption.The exciton generation layer of the OPD in this paper is a blend of acid methyl ester(3-hexylthiophene)and phenyl-C61-butyric acid methyl ester(P3HT:PCBM)which is used to detect visible light,so that the image sensor can be used in gesture recognition,fingerprint or palmprint detection,and X-RAY detection.In this paper,IZO TFT array was fabricated on glass with a back-channel-etch-technique(BCE),and OPD devices were prepared on the top of the IZO TFT by solution process.The leakage current of the IZO TFT is about 5×10-14A,and the mobility of the IZO TFT extracted from the linear region is 11.63 cm2/Vs.The OPD device exhibits the lowest Jd value of 1.9×10-10A/cm2 at-0.05 V,and the maximum of EQE is 33.5%around 500 nm.Based on the characteristics of the IZO TFT and the OPD devices,an image sensor with a pixel size of 50?m and a resolution of 256×256 was designed by using layout tool and fabricated.According to the imaging principle of image sensors,a readout system platform was built.The maximum sensor resolution supported by the readout system is 512×768.The image sensor was tested by the readout system platform.The details of the detected pictures are clear,and the overall quality is satisfactory.By analyzing the electronic noise of the array system,the total electronic noise is calculated to be less than 683 e-.In order to reduce the complexity and cost of sensor preparation,three gate drivers for OPD sensor are designed by using IZO TFT in this paper.(1)Low noise gate driver.The circuit only uses two clock signals,which can effectively reduce power consumption.Through simulation analysis and chip test,the results show that the output waveform of the circuit is stable,and it can almost achieve full voltage swing,and it has good noise suppression characteristics during non-operation.Low noise gate driver can be applied to passive sensor array.(2)Single negative power source gate driver.The circuit can close the pull-down tube well during the working period by using a single negative power supply in the output stage.Through simulation analysis and chip test,the results show that the circuit can output waveform stably at 66.7 k Hz(high level pulse width is 3.2?s),and can be applied to passive sensor arrays with high resolution and high refresh rate.(3)The gate driver with integrated reset control.The circuit can output the reset signal and the row drive signal at the same time without designing the reset control circuit and the row drive signal circuit respectively,which can effectively save the array area and external driving resources.The simulation results of 30-stage circuit show that the output of reset signal and row drive signal are stable,and there is almost no loss in the output waveforms of stage 1 and stage 30.The circuit can be applied to the active image sensor array. |
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