# Enhancing the Photoresponsivity and External Quantum Efficiency of ReSe2 Photodetectors Through the Insertion of a Graphene Auxiliary Layer

## TL;DR

This paper shows that adding a graphene layer improves the performance of ReSe2 photodetectors by boosting their light sensitivity and efficiency.

## Contribution

The novel contribution is the use of a graphene auxiliary layer to significantly enhance the photoresponsivity and quantum efficiency of ReSe2 photodetectors.

## Key findings

- ReSe2/Gr phototransistors show 3.58 times higher photoresponsivity compared to ReSe2 alone.
- The external quantum efficiency is improved by a factor of 3.59 with the graphene layer.
- Enhancements are attributed to better interfacial band alignment and a stronger photogating effect.

## Abstract

Two-dimensional (2D) materials demonstrate significant potential in photodetector technology. They offer high sensitivity, wide spectral range, flexibility and transparency, especially in infrared detection, promising advancements in wearable and flexible electronics. This study explores the application of 2D materials in high-performance photodetectors. Rhenium diselenide (ReSe2) was used as the channel, and graphene (Gr) was inserted between ReSe2 and SiO2 as the gate electrode to enhance device performance. A ReSe2/Gr heterostructure field-effect transistor (FET) was fabricated to investigate the role of Gr in improving the optoelectronic properties of ReSe2 phototransistors. Specifically, the ReSe2 FET without Gr auxiliary layer demonstrates a responsivity (R) of 294 mA/W, an external quantum efficiency (EQE) of 68.75%, and response times as brief as 40/62 ms. Compared with the ReSe2 phototransistor, the ReSe2/Gr phototransistor exhibits significantly improved photoresponsivity and EQE, with the photoresponsivity enhanced by a factor of ap-proximately 3.58 and the EQE enhanced by a factor of approximately 3.59. These enhancements are mainly attributed to optimization of interfacial band alignment and the strengthened photogating effect by Gr auxiliary layer. This research not only underscores the pivotal role of Gr in boosting the capabilities of 2D photodetectors but also offers a viable strategy for developing high-performance photodetectors with 2D materials.