Self-powered Near-infrared Organic Photodiode with Functional Interlayer

The electromagnetic spectrum consists of ultraviolet (100-400 nm), visible (400-750 nm), and infrared (750-2500 nm) regions, among others. The visible region contains the wavelengths that can be seen by the human eye, and infrared light is outside the red edge of this band when the light emitted from any source or heating element is spectrally dispersed. In the infrared band, the electromagnetic waves with the shortest wavelength are referred to as near-infrared rays (750-1000 nm). An organic photovoltaic capable of generating light in the near-infrared wavelength band was fabricated herein through bandgap matching of the photoactive polymer for sensing in the near-infrared region. In addition, the organic photovoltaic was optimized through a newly synthesized functional intermediate layer; this layer constitutes a hole-transport layer that transfers the holes generated by the photoactive layer to the cathode easily. The material traditionally used for the hole-transport layer is PEDOT:PSS, which has the advantages of excellent heat resistance as well as high electrical conductivity and transparency. However, PEDOT:PSS also has drawbacks, such as cost inefficiency, strong acidity, and high hydrophilicity. We have synthesized a polypyrrole polystyrene sulfonate (PPY:PSS) as a hole-transport material that overcomes these disadvantages and optimized it by adjusting the ratio of PPY to PSS. Next, poly[4, 8bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1, 2-b;4, 5-b]dithiophene-2, 6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3, 4-b]thiophene-)-(2-carboxylate-2-6-diyl)]:phenyl-C70-butyric acid methyl ester (PTB7-th:PC70BM) active-layer-based organic photovoltaic was fabricated. Thus, an organic photodiode capable of sensing more effectively in the near-infrared region was developed by inserting the functional interlayer.