High responsivity self-powered flexible broadband photodetector based on hybrid Selenium-PEDOT:PSS junction

Hybrid organic-inorganic composites offer solution processability and ease to construct opto-electronic devices with diverse functionalities, which are desirable for applications like flexible and printed electronics. Trigonal Selenium (t-Se) has been recently investigated for photodetector application, owing to its inherent superior optical properties such as high absorption coefficient and photoconductivity. However, most of the reported Selenium photodetectors use vapor transport based device fabrication techniques which require controlled environments and face scalability issues. In this work, high-performance photodetector based on Selenium-PEDOT:PSS hybrid junction is demonstrated using a facile sonication assisted mechanical mixing and drop-casting technique. XRD and Raman analysis reveals the existence of Selenium in trigonal crystal structure and FE-SEM images show clustered nanoparticles. Selenium is mixed with PEDOT:PSS to form bulk heterojunction, which enhances the electron-hole pair separation efficiency and results in improved device responsivity. Also, due to the favorable band offset between Selenium and PEDOT:PSS which results in built-in field, the photodetector operates in self-biased mode. The device exhibits broad spectral response in UV–Vis–NIR range with responsivities of 0.56 A/W, 66 mA/W and 1.363 A/W at 315 nm, 620 nm and 820 nm, respectively. Response times of 7.7 s, 9.4 s and 6.4 s and external quantum efficiencies (EQE) of 192.58%, 13.25% and 206.55% are obtained for UV, Vis and NIR spectra respectively. Further to validate the robustness, the device is subjected to multiple bending cycles (∼2500) and minimal degradation in performance is observed. Given the simple device architecture and facile device fabrication scheme, this work would enable promising approach for high performance flexible photodetectors.