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Here, we report room temperature deposition of nickel oxide (NiO) thin films on silicon and glass substrates by direct current (dc) magnetron sputtering using a metallic nickel target. The effect of sputtering power (20 W, 25 W, and 30 W) on the thin films, their surface scaling, fractal dimension, and optical properties are extensively investigated. Autocorrelation and height–height correlation functions were applied to AFM images to extract deep insights about the thin films' surfaces. Fractal dimension (D f) was extracted through the power spectral density (PSD) function. Various scaling exponents, including α, β, and 1/z, of the NiO film's surface were independently observed. The local roughness exponent, α, was approximately 0.81 for films deposited with 20 W sputtering power and decreased to 0.71 with higher sputtering power. The interface width (σ) scales with sputtering power (Sp) as ∼ Spβ, with a growth exponent (β) value of 1.17. The lateral correlation length (ξ) follows as ∼ Sp1/z with a 1/z value of 0.703. Additionally, optical parameters were recorded through UV–Vis. optical spectroscopy, and an attempt was made to correlate them with fractal parameters (D f & α). Optical absorption (reflection) increased (decreased) with increasing D f values. The minimum (maximum) reflection (absorption) was observed on the roughest surface (D f = 2.29). The calculated band gap decreased with increasing fractal dimension. This investigation suggests that sputtered surfaces with minimal reflectivity, band gap, and enhanced light-absorbing capacity could potentially be used as active solar layers for advanced optoelectronic devices. [ABSTRACT FROM AUTHOR]

Here we report, the room temperature deposition of silver (Ag) thin films on silicon, glass and silicon solar cell substrates by magnetron sputtering. The effect of thickness on the deposited thin films and their morphological, fractal, optical and solar cell parameters have been extensively investigated. AFM results show that the Ag thin films are composed of different-size of nano-grains and the grain size increases with increasing thickness. Mono-fractal parameters, namely fractal dimension (Df) and Hurst exponent (H), were determined from the power spectral density function. X-ray photoelectron spectroscopy studies indicate that the deposited samples exhibit the presence of oxidation state of Ag (0) in thin films, confirming the stable structure. The optical analysis shows that the transmittance of the deposited thin films decreases with increasing thickness, on the other hand, the silver thin film with thickness of 20 nm shows surface Plasmon resonance (SPR) at 436 nm. Current-voltage (I–V) curves were measured in dark and under illumination mode at standard testing conditions, i.e., 300K, 1000 W/m2 and 1.5 AM global using a solar simulator. These measurement studies indicate that thicknesses are effectively impacts on photovoltaic performance. The calculated values of change in solar efficiency (Δ η) are 0.26, −0.20, −0.76 and −6.88 % for thin films with nominal thickness 0.5, 1, 2 and 20 nm respectively. • Ag thin films were deposited by magnetron sputtering technique. • The influence of ultrathin layers on the fractal dimensions of Ag films was studied. • The influence of ultrathin layers on the optical properties of Ag films was studied. • The influence of ultrathin layers on the solar cell performance have been explored. • The influence of optical parameters viz. reflection, plasmonic on solar cell efficiency have been studied. [ABSTRACT FROM AUTHOR]

• The design and fabrication of high desirable NiOx/Si heterojunction is proposed. • Thickness-dependent analysis of optical behavior to understand the diode performance. • The influence of grain size on diode performance have been explored. • The proposed Sn/p-NiOx/n-Si/Al heterojunction improved the diode parameters. The effect of grain size on optical properties and designed Ag/p-NiOx/n-Si/Al-based Schottky diode have been investigated. The XRD patterns are used to calculate the grain size of NiOx film, which increases with increasing thickness. Fractal dimensions were estimated from the power spectral density (PSD) algorithm using AFM images. The band gaps were calculated from recorded transmission spectra, showing the reduction of band gap from 3.88 eV to 3.67 eV with increasing grain size. The effect of grain size on the performance of Ag/p-NiOx/n-Si/Al-based Schottky-diodes are analyzed through I-V measurement. The diode parameters of the designed device were calculated using the thermionic emission, Norde, and Cheung models. It is found that the reduction of barrier height of the Schottky diode from 0.95 eV to 0.84 eV with increasing grain size of NiOx films. It is found that the grain size of film strongly impacted on the diode parameters, such as ideality factor (η), potential barrier (φ h), series resistance (Rs) performance. [ABSTRACT FROM AUTHOR]