Electrical and Optical Characteristics of Self-Powered Colloidal CdSe Quantum Dot-Based Photodiode

Abstract

In this paper, a novel self-powered Schottky photodiode has been proposed, which uses the low-temperature processing (~250°C) and the implementation of colloidal quantum dots (QDs)-based charge transport layer (ZnO QDs). The self-powered Schottky photodiode has been fabricated on the n-Si <;111> substrate, and the colloidal CdSe QDs have been used as an active layer. The Schottky junction has been formed by depositing Gold (Au) on the CdSe QDs by the thermal evaporation method. The CdSe QDs (~30 nm) thin film is assumed to be fully depleted (> 85%) by the Au Schottky contact with the measured effective barrier height of 0.67 eV and built-in potential of 0.34 V. The photoresponse of the selfpowered Schottky photodiode has been measured, and the maximum responsivity of 10.23 mA/W and a maximum detectivity of 8.81 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> cmHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> /W at ~522 nm have been achieved. The self-powered Schottky photodiode shows a transient response (t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 17.9 ms and t <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> = 18.0 ms) under the pulsating white LED light at an on-off period of 1 s.