Abstract
We report on the microelectronic characteristics of a novel hybrid heterojunction device based on a solution processable semiconducting polymer poly(9,9-dioctylfluorenyl-2,7-diyl)- co-(N,N0-diphenyl)-N,N′di(p-butyl-oxy-pheyl)-1,4-diamino-benzene) (PFB) and p-type silicon (p-Si). The PFB/p-Si heterojunction is prepared by spin coating 20 mg/mL solution of PFB in chloroform on the precleaned polished surface of p-Si substrate. Thermal evaporation of silver (Ag) electrode on top of PFB completes the fabrication of the Ag (90 nm)/PFB (180 nm)/p-Si heterojunction device. Morphology of PFB thin film is studied by using an atomic force microscope (AFM) and scanning electron microscope (SEM), which reveals grains are randomly distributed with slightly different grain sizes and shapes. It leads the film to form nonuniformity and some roughness in its topography that results in limiting the current (I) flow across the film/interface with p-Si. Ultraviolet (UV–vis) absorption and X-ray diffraction (XRD) spectra are measured for optical bandgap and crystal structure analysis of PFB. The key microelectronic parameters—rectification ratio (RR), ideality factor (n), barrier height (Φb), series resistance (Rs) and reverse saturation current (I0)—of the Ag/PFB/p-Si heterojunction are found from current–voltage (I–V) characteristics at room temperature (300 K) in dark conditions (≈0 lux). The Ag/PFB/p-Si heterojunction device exhibits improved microelectronic parameters when compared to those of earlier reported devices that were prepared in the same configuration. This improvement in the device parameters reveals enhancement in the microelectronic properties across the interface/depletion region of the Ag/PFB/p-Si device, which can be attributed to the remarkable electronic properties of PFB such as its relatively high hole mobility and better charge carriers’ conduction. The charge transport mechanisms through the device is also studied. Having the smaller values of I0 ≈ 7 × 10−10 A and n ≈ 3.23, as well as higher shunt resistance (Rsh) of 32 GΩ for the Ag/PFB/p-Si device suggest its potential for many electronic and optoelectronic applications.
Highlights
Organic semiconductors are one of the most favorable emerging materials for their possible applications in electronic, optoelectronic, thermoelectric, and photonic devices [1,2,3,4,5]
Organic semiconductors possess exciting electrical and optoelectronic properties due to its pi (π)-conjugated molecular structure that permits the conduction of charge carriers through a hopping process [10]
The inorganic hybrid sensors. Current–voltage (I–V) graph shown in Figure 4a is nonlinear and asymmetric, which demonstrate that p-Si/PFB heterojunction exhibits rectifying current behavior in the forward bias
Summary
Organic semiconductors are one of the most favorable emerging materials for their possible applications in electronic, optoelectronic, thermoelectric, and photonic devices [1,2,3,4,5]. Organic semiconductors possess exciting electrical and optoelectronic properties due to its pi (π)-conjugated molecular structure that permits the conduction of charge carriers through a hopping process [10] They offer several distinct properties of their kind, which include mechanical flexibility, solubility in various organic solvents, easy processing for device fabrication (spin coating, drop casting, inkjet printing, etc.), chemical as well as thermal stabilities, and relatively low-cost, when compared to inorganic semiconductors [11,12]. The structure of the hybrid organic–inorganic heterojunction is of great importance due to the fact that it utilizes the higher charge carrier mobility of an inorganic semiconductor and its solution processing ability, as well as the easy fabrication process of organic semiconductor thin films for device fabrication These hybrid heterojunctions provide an excellent platform for wide-range and superior applications by employing desired organic materials that possess interesting optoelectronic properties, remarkable scalability, and high flexibility. The morphological, structural, and optical properties are studied to understand surface features, crystallinity, and bandgap of the PFB thin films
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