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Application of Spray Pyrolysis | ZnO Deposition

Spray pyrolysis is a processing technique which is used to prepare thin films and thick films, ceramic coatings, and powders. It has many advantages, such as inexpensive and simple experimental setup, easy control of chemical specimens, reproducibility, and uniform and large area coating. More about spray pyrolysis ZnO thin films…

Spray Pyrolysis Vs Vacuum Based Deposition

Metal oxide semiconductors like ZnO offer numerous advantages over competing technologies (e.g., organics, amorphous silicon) like high optical transparency, mechanical flexibility, processing versatility, etc. ZnO semiconductors are usually processed by vacuum-based techniques such as molecular beam epitaxy (MBE), chemical vapor deposition, ion-assisted deposition and pulsed laser deposition. However, vacuum-based deposition techniques have high manufacturing cost and their incompatibility with large area deposition.

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Spray Pyrolysis ZnO

When ZnOis deposited by spray pyrolysis, it has good quality smooth films at temperatures above 300 °C and the crystallite size of it increases with temperature from 7.5 to 32 nm within the temperature range between 200 − 500 °C.

The FWHM values of spray pyrolysis prepared ZnO (59, 67 and 123 meV for 500 °C, 400 °C and 300 °C respectively) are comparably lower than the values reported by heteroepitaxial grown (∼ 117 meV), RF magnetron sputtered ZnO film (∼ 75 meV) and bulk ZnO (∼ 115 meV).

Excellent Operating Characteristics

These ZnO Thin-Film Transistors exhibit excellent operating characteristics with a maximum electron mobility of 25 cm2 V−1 s−1 and current on/off ratio on the order of 106. ZnO films grown at substrate temperatures in the range of 400–500 °C exhibit the highest electron mobilities with maximum average values in the range 20–25 cm2 V−1 s−1.

IR-Heating-Dip-Coater-for-Metal-Coating

IR Heating Dip Coater for Metal Coating

Organic light-emitting diodes (OLED) is a flat light emitting technology, which has attracted considerable attention in the industry, due to their eco-friendly nature, low power consumption, better durability, self-illumination and improved image quality. Conventionally vacuum evaporation method is used to prepare OLED electrodes but it has complicated vacuuming processes and low economic efficiency. Here IR heating Dip Coater can be used.

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These silver electrodes can be easily prepared by the dip-coating method and sintering the silver film by infrared process. This process is not only energy efficient but also economically feasible.

IR heating Dip Coater Process

Silver electrode films were prepared by dip-coating after setting the cycles and the rates of pull-ups and other parameters. Polyvinylpyrrolidone (PVP) is used as the stabilizer as well as the anisotropic agent. Infrared is used to achieve the sintering of the dip-coated silver films. The silver electrode is directly irradiated and sintered by infrared light from the top side. It promotes the deformation of PVP on the surface of silver nanoparticles and improves the conductivity of the silver film. As the silver particles are in close contact, due to infrared light, conductivity and flatness of silver electrodes is improved. In conventional sintering at 250°C for 30 min, a silver film with a sheet resistance 0.94 Ω sq−1 is be obtained. While in infrared sintering at 250 W for 30 min, the sheet resistance becomes 0.89 Ω sq−1. Conductivity of silver film can be increased by increasing irradiating power and time in infrared sintering.

Applications Of IR Heating With Spin Coater

Applications Of IR Heating With Spin Coater

Spin coating is an easy and fast method to generate uniform thin films and is commonly preferred in deposition of polymers, nanoparticles, biomaterials, etc. The method of IR-irradiation during spin coating provides impressive potential in scientific environments. In a single coating step of hybrid suspension, IR heating causes an increase in layer thickness by more than 3 times. It also accelerates the aging which leads to faster gelation, thus the sol – gel – transition occurs after a shorter period of time. For perovskite thin film…

Applications Of IR Heating With Spin Coater - perovskite thin film coating
Spin coating as a thin film deposition technique

Perovskite thin film using spin coating equipment

In fabrication process of perovskite, air humidity was just 25% with infrared heating while it was about 55% without IR. The air humidity could significantly impact the morphology of the prepared perovskite. Perovskite thin film prepared with infrared heating presented compact and uniform, with grain size of CH3NH3PbI3 estimated to be 220 nm. While without infrared heating, it was rough and leaky. The resistance of the perovskite absorber layer prepared device with infrared heating exhibited low series resistance (Rs) and high shunt resistance (Rsh) compared to that of without infrared heating. Rs and Rsh is beneficial for charge extraction and transport.

The rough and highly porous scaffold m-TiO2 thin film was proved to be an excellent host material for perovskite growth and its thickness can affect the perovskite deposition. The infrared heating applied during the process not only can low the ambience moisture, but also can offer stereoscopic uniform thermal radiation to warm up the m-TiO2 layer. The warmed m-TiO2 layer helps to get the uniform perovskite. The uniform absorber layer is quite important since perovskite solar cells prepared by traditional methods often suffer from inadequate filling of perovskite at the bottom, which increases the recombination of carriers leading to decrease in efficiency in solar cells.

IR heating also helps to prepare good quality perovskite absorber layer with decreased annealing temperature and avoids high intensity light annealing process. The approach of using IR-irradiation during the spin coating process to control evaporation in solvent-based systems and improving layer thickness is very promising.

By V.R. NIVEDHA SHALINI