Flexible and low-voltage organic phototransistors

Abstract

A stripping procedure was demonstrated for the preparation of an ultra-smooth aluminum electrode. After potentiostatic anodization and treatment with a self-assembled monolayer (SAM) of n-octadecyl phosphonic acid, AlO_x–SAM hybrid dielectrics were grown onto flexible, stripped aluminum combining low cost manufacture under ambient conditions with excellent dielectric characteristics (negligible leakage, 114.3 nF cm⁻² capacitance). Field effect transistors using dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) as an organic semiconductor can be operated below −5 V with a high mobility of 0.53 cm² V⁻¹ s⁻¹, high on/off current ratio of 1.7 × 10⁵, low subthreshold slope of 210 mV dec⁻¹, and good threshold of −1.51 V. Moreover, the DNTT transistor showed a good photoresponse to blue light with a wavelength of 450 nm, with photoresponsivity (R) of 50 A W⁻¹ and a photocurrent/dark current ratio (P) of 5 at a light intensity of 5 μW cm⁻².