Low-voltage Driving Phototransistor Based on Dye-sensitized Nanocrystalline Titanium Dioxide Thin Films

TL;DR

This paper presents a low-voltage dye-sensitized nanocrystalline titanium dioxide phototransistor with linear light response, moderate photosensitivity, and potential for optical switching and communication applications.

Contribution

It introduces a novel low-voltage photo-gated transistor based on dye-sensitized TiO2 with detailed analysis of its electrical and optical properties.

Findings

Maximum photosensitivity of ~0.1 A/W

Cut-off frequency of ~50 Hz

Linear dependence of response current on light intensity

Abstract

Photo-gated transistors based on dye-sensitized nanocrystalline titanium dioxide thin film are established. A transistor-like transport behavior characterized by the linear increase, saturated plateau, and breakdown-like increase in the voltage-current curve is achievable with a low driven bias for the present device. The response current exhibits a linear dependence on the intensity of gated light, and the measured maximum photosensitivity is approximately 0.1 A/W. The dynamic responses for various light frequencies and their dependences on the load resistances are investigated as well. The cut-off frequency of ~50 Hz is abstracted, indicating the potential application for economical and efficient light switch or optical communication unit. The dc photo-gated response is explained by the energy level diagram, and is numerically simulated by an equivalent circuit model, suggesting a clear correlation between photovoltaic and photoconductive behaviors as well as their optical responses.