Effect of Substrates on Structural, Morphological, Optical and Electrical Characteristics on Poly (9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) Thin Films

Abstract

Polymer light-emitting diodes using organic-inorganic heterojunctions have a lot of benefits such as excellent blue-light emission, simple fabrication procedure, and low processing cost. We report on the effect of substrates on the fabrication of poly (9,9-di-noctylfluorenyl-2,7-diyl) or (PFO) thin films and their characterization as a simple light-emitting diode (LED) structure. The structural properties of the thin films were characterized using X-ray Diffraction (XRD). The morphological properties of the thin films were studied using Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscopy (AFM). The XRD results demonstrated the formation of amorphous PFO structure, with no presence of the crystalline phase of PFO. The FESEM images showed the formation of cracks due to evaporation from annealing. Optical characteristics were studied using ultravioletvisible (UV-Vis) spectroscopy, Photoluminescence (PL) and reflectance measurements showing the presence of β phase of PFO, important for charge carrier mobility. Thin films deposited on ITO-coated glass, FTO-coated glass and Silicon n-type ( 110) and ( 111) orientation substrates were used to fabricate a simple LED structure. The devices fabricated using Si n-type substrates showed p-n junction characteristics and was a better substrate choice than ITO or FTO coated glass.

Highly Sensitive UV Photodiode Composed of β-Polyfluorene/YZnO Nanorod Organic-Inorganic Hybrid Heterostructure

“…For the PL characteristics, the PFO layer clearly reveals a huge blue-emission peak (P3) at ~470 nm with a broad hump (P4) at ~540 nm ( Figure 2 b). These correspond to the typical PL feature of β -phase PFO [ 41 , 43 ] that comprises a flatter geometry of backbone-like PFO molecules. Namely, the PFO layer was well-dispersed along the surface direction.…”

“…To investigate the intrinsic properties of PFO, we prepared the reference sample of the pristine PFO layer by coating it onto the SiO 2 /Si substrate. The PFO layer displays a grain-aggregated topography (see the inset of Figure 2 b), resulting from the volume shrinkage during the thermal treatment [ 41 ]. For the PL characteristics, the PFO layer clearly reveals a huge blue-emission peak (P3) at ~470 nm with a broad hump (P4) at ~540 nm ( Figure 2 b).…”

“…For instance, multi-level memory cells [ 36 , 37 ], high speed barristors [ 38 ], color-tunable light-emitting diodes [ 18 , 39 ], and color-dependent photodiodes [ 40 ] are typical examples of ZnO-based inorganic-organic hybrid electronic and optoelectronic devices. Among various organic semiconductors, β-phase polyfluorene (PFO) is of ample interest particularly for optoelectronic device applications because of its wide band-gap energy and good processability [ 41 , 42 , 43 ]. Furthermore, since β-phase PFO has a higher charge-carrier mobility than other organic semiconductors [ 44 ], many researchers have been devoted to demonstrating highly efficient solid-state light-emitting devices using the inorganic-organic hybrid heterostructure of ZnO/PFO [ 45 , 46 , 47 , 48 , 49 ].…”

Insights into the β‐phase of polyfluorene: characterization, regulation, and mechanism

“…[8][9][10][11] PFO, exhibiting high photoluminescence efficiency, wide stimulated emission interval and so on, which make it highly valuable for scientists. [12][13][14][15][16][17] PFO have the absorption peak at around 380 nm in dilute solution and is less influenced by the substituent. The methylene group at the 9-position is more reactive and can be easily modified.…”

“…However, among the numerous conjugated polymers that have been synthesized, only a few can emit blue light effectively, such as polyacetylene (PA), polyaniline (PAn), polythiophene (PTh), polypyrrole (PPy), polystyrene (PPP), polystyrene (PPV), and polyfluorene (PFO) 8–11 . PFO, exhibiting high photoluminescence efficiency, wide stimulated emission interval and so on, which make it highly valuable for scientists 12–17 . PFO have the absorption peak at around 380 nm in dilute solution and is less influenced by the substituent.…”