Visible-blind ultraviolet sensitive photodiode with high responsivity and long term stability

A high responsivity organic visible-blind ultraviolet photodiode is achieved using aluminum (III) bis(2-methyl-8-quinolinato)4-phenylphenolate (BAlq) and 4,4',4 ''-tri-(2-methylphenyl phenylamino) triphenylaine (m-MTDATA) as the electron acceptor and donor, respectively. Under 365 nm illumination with an intensity of 1.2 mW/cm(2), the photodiode behaves a maximum photoresponse of 514 mA/W at -7 V, which is markedly higher than previous reports in our group by Su et al. [Appl. Phys. Lett. 93, 103309 (2008)] and inorganic counterparts based on GaN (150 mA/W) and Si (120 mA/W), respectively. The operational time of the unsealed photodiode is larger than 1000 min when the photocurrent decreases to 67% of its original intensity in air environment. Harvest of so high performance photodiode is mainly attributed to the larger band offsets at m-MTDATA/BAlq heterojunction and skillful device design, etc. The improvement mechanisms are also augured in detail. (C) 2010 American Institute of Physics. [doi:10.1063/1.3463483]