Nanomaterials 2022, 12, 475. https://doi.org/10.3390/nano12030475 www.mdpi.com/journal/nanomaterials Article Highly-Responsive Broadband Photodetector Based on Graphene-PTAA-SnS2 Hybrid Guigang Zhou 1,2,† , Huancheng Zhao 3,† , Xiangyang Li 4 , Zhenhua Sun 2 , Honglei Wu 2 , Ling Li 3, *, Hua An 1,2, *, Shuangchen Ruan 3 and Zhengchun Peng 1,2 1 Center for Stretchable Electronics and NanoSensors, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; 2176285304@email.szu.edu.cn (G.Z.); zcpeng@szu.edu.cn (Z.P.) 2 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; szh@szu.edu.cn (Z.S.); hlwu@szu.edu.cn (H.W.) 3 Shenzhen Key Laboratory of Laser Engineering, College of Physics and Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; 1800281011@email.szu.edu.cn (H.Z.); scruan@szu.edu.cn (S.R.) 4 Key Laboratory of Advanced Optical Precision Manufacturing Technology of Guangdong Higher Education Institutes, College of Applied Technology, Shenzhen University, Shenzhen 518060, China; 2170285209@email.szu.edu.cn * Correspondence: liling@szu.edu.cn (L.L.); huaan@szu.edu.cn (H.A.) † These authors contributed equally to this work. Abstract: The development of wearable systems stimulate the exploration of flexible broadband photodetectors with high responsivity and stability. In this paper, we propose a facile liquid-exfoli- ating method to prepare SnS2 nanosheets with high-quality crystalline structure and optoelectronic properties. A flexible photodetector is fabricated using the SnS2 nanosheets with graphene- poly[bis(4-phenyl) (2,4,6-trimethylphenyl) amine (PTAA) hybrid structure. The liquid-exfoliated SnS2 nanosheets enable the photodetection from ultraviolet to near infrared with high responsivity and detectivity. The flexible broadband photodetector demonstrates a maximum responsivity of 1 × 10 5 A/W, 3.9 × 10 4 A/W, 8.6 × 10 2 A/W and 18.4 A/W under 360 nm, 405 nm, 532 nm, and 785 nm illuminations, with specific detectivity up to ~10 12 Jones, ~10 11 Jones, ~10 9 Jones, and ~10 8 Jones, re- spectively. Furthermore, the flexible photodetector exhibits nearly invariable performance over 3000 bending cycles, rendering great potentials for wearable applications. Keywords: flexible photodetector; SnS2 nanosheets; high responsivity 1. Introduction Flexible optoelectronic devices have attracted considerable attentions due to their potential applications in wearable systems [1–4], imaging sensing [5], and communica- tions [6], where especially flexible broadband photodetectors with high responsivity and stability are highly desired. However, the complexity and high cost of traditional rigid materials limit their extensive applications in flexible devices [7]. In the past decades, two- dimensional (2D) materials, such as phosphorenes, transition-metal dichalcogenides (TMDCs), and IV-VI group semiconductors, have been widely investigated in solar cells [8], photodetectors [9–11], etc. Moreover, 2D semiconductors are particularly suitable as active channel materials in wearable optoelectronic devices owing to their atomically thin structure, mechanical flexibility, strong in-plane covalent bonding, and excellent electrical and optoelectronic properties [12,13]. In addition, their compatibility with other materials, including organic semiconductors [14,15], quantum dots [16,17], nanosheets [18], perov- Citation: Zhou, G.; Zhao, H.; Li, X.; Sun, Z.; Wu, H.; Li, L.; An, H.; Ruan, S.; Peng, Z. Highly-Responsive Broadband Photodetector Based on Graphene-PTAA-SnS2 Hybrid. Nanomaterials 2022, 12, 475. https:// doi.org/10.3390/nano12030475 Academic Editor: Filippo Giubileo Received: 31 December 2021 Accepted: 26 January 2022 Published: 29 January 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).