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The photoresponse of polymer field-effect transistors (PFETs) based on the 2,5-bis(dibutylaminostyryl)-1,4-phenylene-b-alkyne-b-1,4-bis(2-ethylhexyl)benzene terpolymer (BAS-PPE) is investigated. BAS-PPE is a photoluminescent conducting polymer with a band gap of 2.25 eV. The BAS-PPE PFETs were fabricated using an open coplanar configuration and light is illuminated onto the top side of the PFETs with no shadowing present. A sweep of VDS demonstrates that IDS saturation is suppressed during illumination, which suggests that pinch-off cannot be reached since the injected photogenerated carriers continue unabated. Also, with incident light, the channel cannot be turned off, even at high positive gate biases, due to the accumulation of photogenerated carriers. A sweep of VDS shows that BAS-PPE can act as a p-type polymer and favors hole injection and transport. A sweep of VGS shows an increase in IDS with different light intensities. The Ilight/Idark ratio reaches as high as about 6000 at an incident light intensity of 4 μW and a photoresponsivity of 5 mA/W is calculated. [ABSTRACT FROM AUTHOR]