Organic-inorganic hybrid diodes are very promising for solution processing, low cost, high performance optoelectronic devices. Here, we report a high quality p-n heterojunction diode composed of n-type inorganic SbS and p-type organic 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) with a rectification ratio of ∼10 at an applied bias of 1 V. On illumination with visible light (470 nm, 1.82 mW/cm), the current value in our device becomes 8 × 10 times that of its dark value even at a zero bias condition. The estimated responsivity value at zero bias is 0.087 A/W which is so far the highest reported for any organic-inorganic hybrid photodiode, to the best of our knowledge. It also exhibits a fast photoresponse time of <25 ms (instrumental limit). More importantly, our device can also detect visible light with power density as low as 8 μW/cm with a photocurrent density of 1.2 μA/cm and a photocurrent to dark current ratio of more than 8. We also demonstrate that the values of responsivity, short circuit current, and open circuit voltage of the photodetector can be improved significantly using a thin layer of TiO hole-blocking layer. These findings suggest SbS/spiro-OMeTAD heterojuncton as a promising candidate for efficient self-powered low visible light photodetector.

A peptide appended perylene bisimide (PBI)based new hydrogel has been discovered in phosphate buffer medium having the pH ranging from 7.00 to 9.00. This peptide appended PBI-derivative shows interesting photoswitching property in the aggregated state. This gel is thoroughly characterized by UV−visible absorption and fluorescence spectroscopy, field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and rheological studies. TiO 2 nanoparticles are also prepared by using a protein amino acid, glutamic acid, in water medium. The as-synthesized TiO 2 nanoparticles exhibit usual photoswitching behavior. An organic−inorganic hybrid nanomaterial is prepared by incorporating the as-synthesized TiO 2 nanoparticles into the fibrillar gel network of the native gel. This TiO 2 −PBI-based hybrid soft material shows a characteristic of nanofiber and nanoparticle combination in their nanoscale coassembled state as it is evident from the respective TEM images of the hybrid material. Interestingly, this nanohybrid shows improved photoswitching properties (photocurrent gain) compared to that of its individual constituents (TiO 2 nanoparticles and PBI-based xerogel). The increase in photoswitching property holds a future promise for making a new organic−inorganic hybrid material for the optoelectronic device application with a high photocurrent conversion efficiency.

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