Photo-Response of Low Voltage Flexible TIPS-Pentacene Organic Field-Effect Transistors

Photo-response of solution processed flexible TIPS-pentacene organic field-effect transistors is evaluated under illumination with visible light of red, green, and blue colors having minimum wavelengths of 620, 520, and 460 nm. For -10 V operation, pristine photo-OFETs exhibited average field-effect mobility of 0.11 cm
²
V
^-1
s
^-1
, near zero threshold voltage, and current ON-OFF ratio of ~105. These photoOFETs exhibited prevalent photovoltaic characteristics with shift in the threshold voltage upon illumination, which was found to increase with rising intensity, illumination time, and gate bias during illumination. For low-voltage operation at -5 V, maximum current modulation of 4 × 10
⁴
and 10
²
, and photoresponsivity of 17 mA/W and 35 mA/W, respectively, were achieved for blue (intensity of 1.7 mW/cm
²
) and green (intensity of 0.4 mW/cm
²
) light illuminations. However, these photo-OFETs did not show significant response to red light. A fast dynamic response to periodic pulses of illumination was also observed. For a gate bias of +10 V and illumination time of 500 s, maximum current modulation of 105 was achieved for blue light illumination.