Enhanced photomultiplication effect in P-N-P structure for ultrasensitive and stable deep-ultraviolet detection

초록

A photomultiplication photodetector (PM PD) with enhanced sensitivity to ultraviolet B (UVB) radiation has been developed in this study. We demonstrate that the trap-assisted PM effect in a vertical p-n-p structure can be significantly amplified by incorporating an electron-blocking layer (EBL) of poly[(9,9-dioctylfluorenyl-2,7-diyl)co-(4,4 '-(N-(4-sec-butylphenyl)diphenylamine)] (TFB) thin film, at an optimized thickness. The enhanced trapassisted PM effect is evidenced by (i) the higher-than-one exponent in the non-linearity between photocurrent and incident light intensity; and (ii) a positive-to-negative capacitance switching upon application of an external voltage. Hence, the PM PD achieved a high performance with a responsivity of 4.3 A W-1 and a specific detectivity of 3.47 x 1013 Jones. Moreover, our device exhibited high stability under long-term exposure to energetic UV light. For practical applications, the device could rapidly identify the presence of weak UVB emission from organic flames. This finding provides a new platform to develop ultrasensitive PDs for diverse practical applications in need of detecting deep-UV light at low intensity.

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