Photosensitive Field-Effect Transistor with Enhanced Photoamplification Mediated by Charge Transfer in a Heterostructure of α-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mrow><mml:mi>Cs</mml:mi><mml:mi>Pb</mml:mi><mml:mi mathvariant="normal">I</mml:mi></mml:mrow><mml:mn>3</mml:mn></mml:msub></mml:math> Nanocrystals and Two-Dimensional <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:msub><mml:mi>WS</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>

Abstract

Hybrid heterostructure-based phototransistors are attractive owing to their high gain induced by the photogating effect. However, the absence of an in-plane built-in electric field in the single-channel-layer transistor results in a relatively higher dark current and requires a large operating gate voltage of the device. Here, we report air-stable cesium lead iodide/tungsten di-sulfide (${\mathrm{Cs}\mathrm{Pb}\mathrm{I}}_{3}/{\mathrm{WS}}_{2}$) mixed-dimensional heterostructure-based photo-field-effect-transistors (photo-FETs) with asymmetric metal electrodes ($\mathrm{Cr}/{\mathrm{WS}}_{2}/\mathrm{Au}$), exhibiting extremely low dark current (approximately ${10}^{\ensuremath{-}12}$ A) with a responsivity of approximately ${10}^{2}$ A/W at zero gate bias. The Schottky-barrier- (${\mathrm{WS}}_{2}/\mathrm{Au}$ interface) induced rectification characteristics in the channel accompanied by the excellent photogating effect from solution-processed \ensuremath{\alpha}-phase ${\mathrm{Cs}\mathrm{Pb}\mathrm{I}}_{3}$ nanocrystal sensitizers, resulting in gate-tunable broadband photodetection with a very high responsivity (approximately ${10}^{4}$ A/W) and excellent sensitivity (approximately ${10}^{6}$). Most interestingly, the device shows superior performance even under high-humidity (50--65%) conditions owing to the formation of cubic \ensuremath{\alpha}-phase ${\mathrm{Cs}\mathrm{Pb}\mathrm{I}}_{3}$ nanocrystals with a relatively smaller lattice constant (a = 6.2315 \AA{}) and filling of surface vacancies (${\mathrm{Pb}}^{2+}$ centers) with the sulphur atoms from the ${\mathrm{WS}}_{2}$ layer, thus protecting it from environmental degradation. These results emphasize an exciting strategy for developing mixed-dimensional hybrid heterostructure-based phototransistors for futuristic integrated nano-optoelectronic systems.

Topics & Concepts