【Member Papers】A graphene-enhanced PEDOT:PSS/β-Ga₂O₃ microwire organic–inorganic hybrid heterojunction self-driven photodetector with high light responsivity

      Researchers from the Northeast Normal University have published a dissertation titled "A graphene-enhanced PEDOT:PSS/β-Ga₂O₃ microwire organic–inorganic hybrid heterojunction self-driven photodetector with high light responsivity" in Journal of Materials Chemistry C.

Project Support

      This work was supported by the National Natural Science Foundation of China (no. 62274027 and 62404039), the Open Research Fund of Song Shan Lake Materials Laboratory (2023SLABFK03), the 111 Center (B25030), the funding from Jilin Province (no. 20220502002 GH), the Postdoctoral Fellow ship Program of CPSF (GZC20230416), and the Fundamental Research Funds for the Central Universities (2412024QD010).

Background

      Deep ultraviolet (DUV) photodetectors have attracted significant attention due to their ability to operate within the 200–280 nm solar-blind range, where solar radiation is absorbed by the atmosphere, eliminating background interference and making them valuable for applications such as flame monitoring, missile detection, ozone studies, and medical diagnostics. Candidate materials include AlGaN, ZnO, and β-Ga₂O₃, with β-Ga₂O₃ being particularly promising because of its intrinsic solar-blind bandgap (~4.9 eV). Self-powered photodetectors are of special interest due to their portability, environmental friendliness, and ability to operate without external bias, with performance depending critically on the internal electric field for efficient photocarrier separation and transport. Challenges for β-Ga₂O₃-based devices include the lack of p-type doping and intrinsic defects such as oxygen vacancies and dislocations, which can significantly degrade device performance. To address this, researchers have explored pn heterojunction photodetectors combining β-Ga₂O₃ with inorganic p-type semiconductors (e.g., GaN, NiO, Cu₂O) or organic semiconductors (e.g., PEDOT:PSS), the latter offering advantages in mechanical flexibility, low cost, and integration into wearable systems. Recent strategies introduce graphene into PEDOT:PSS to enhance conductivity and the built-in electric field, and combine this with high-quality CVD-grown β-Ga₂O₃ microwires to fabricate self-powered DUV photodetectors, achieving high responsivity and detectivity at zero bias, providing a viable route for the development of high-performance flexible DUV photodetectors.

Abstract

      In this study, a PEDOT:PSS@graphene composite structure was engineered by incorporating graphene into PEDOT:PSS, thereby significantly enhancing its electrical conductivity. This composite layer was subsequently integrated with high-crystallinity β-Ga₂O₃ microwires (MWs), synthesized via chemical vapor deposition (CVD), to fabricate a self-powered deep-ultraviolet (DUV) photodetector. The device exhibited an ultra-low dark current of only 0.13 pA under a bias of 10 V, highlighting its superior noise suppression capability. More importantly, under 245 nm illumination at a bias of 0 V, the photodetector demonstrated a remarkable responsivity of 65 mA W⁻¹, which represents enhancements by factors of 48 and 4 compared with PEDOT:PSS/β-Ga₂O₃ MW and graphene/β-Ga₂O₃ MW heterostructures, respectively. In addition, the device achieved a high specific detectivity of ∼10¹² Jones. These outstanding photoresponse characteristics can be primarily attributed to the incorporation of graphene, which improves the conductivity of the PEDOT:PSS layer while simultaneously strengthening the built-in electric field at the heterojunction interface, thereby facilitating more efficient separation and transport of photogenerated carriers. Overall, this work demonstrates a promising strategy for designing organic–inorganic hybrid heterostructures and offers new insights into the development of high-performance, self-driven solar-blind photodetectors.

Conclusion

      In summary, the incorporation of graphene into PEDOT:PSS successfully yielded a PEDOT:PSS@graphene composite structure, which enhanced the conductivity of the PEDOT:PSS film by two orders of magnitude. Based on this material, a high performance self-powered solar-blind DUV photodetector was constructed using the PEDOT:PSS@graphene/β-Ga₂O₃ MW organic–inorganic hybrid p–n heterojunction. The introduction of graphene effectively improved the conductivity of PEDOT: PSS, reinforced the built-in electric field at the heterojunction interface, and consequently enhanced the overall device per formance. Under a bias of 0 V and 245 nm illumination, the photodetector demonstrated a notable photo-to-dark current ratio of 10³, an ultrahigh responsivity of 65 mA W^-1, and a specific detectivity of 9×10¹¹ Jones. These results underscore the efficacy of the proposed strategy. This study offers valuable insights for future performance optimization of self-powered solar-blind DUV photodetectors based on organic–inorganic hybrid heterojunctions and provides a useful reference for further research toward developing more efficient and sensitive photodetection devices.

Fig. 1 (a) Optical image of a single β-Ga₂O₃ on a SiO₂/Si substrate, and the inset shows a photograph of β-Ga₂O₃ in a corundum boat; (b) the XRD pattern of β-Ga₂O₃, the inset shows an enlarged view of the (400) peak; (c) transmission spectrum of β-Ga₂O₃ MWs; (d) the SEM image of β-Ga₂O₃ MW and the inset shows the cross-sectional view of β-Ga₂O₃ MW; (e) mapping of Ga and O elements in a single β-Ga₂O₃ MW; (f) EDAX of a single β-Ga₂O₃ MW.