The Effect of Different Precursor Solutions on the Structural, Morphological, and Optical Properties of Nickel Oxide as an Efficient Hole Transport Layer for Perovskite Solar Cells

Abstract

Perovskite solar cell (PSC) technologies have recently become a popular research topic. The hole transport layers (HTL) are important in establishing stable and efficient PSC by regulating charge absorption, interlayer recombination losses, and band alignment. Spiro-OMeTAD was extensively used as the HTL to fabricate highly efficient PSCs. Despite Spiro-OMeTAD having the benefit of providing high PCEs, it is costly, hazardous to the ecology, and cannot provide high efficiencies in the lack of additional additives that can reduce their stabilities. Inorganic HTL, specifically nickel oxide (NiO), has garnered much interest due to its low-cost, enhanced mobility, and strong stability to attain high efficiency. This study investigated different precursor solutions of NiO synthesis (Method I, II, and III) and deposited using the spin coating approach. The films were annealed at different annealing temperatures (400°C, 550°C, and 700°C) and evaluated by X-ray powder diffraction (XRD), UV-Vis spectroscopy, and Scanning electron microscopy (SEM) to test their structural, morphological, and optical characteristics, respectively. The findings of XRD revealed that a higher annealing temperature increases the crystallite size and decreases the microstrain through the study from Scherrer’s and Williamson-Hall’s (WH) equations. From the SEM analysis, the films show uniformity, large crystals, and agglomeration of particles. The annealing temperature from 400°C to 700°C reduced bandgap energy from 3.6 eV to 2.1 eV. According to the result, NiO produced at an annealing temperature of 700°C (Method I) exhibited the best characteristics and might be a viable option for HTL in PSCs.

Analysis of effect of annealing at high temperature on nickel oxide and zinc oxide thin film for solar cell applications

“…The plot of (αhv)2 vs. hv indicated in Figure 8(b) shows that ZnO has band gaps of 4.17 eV, 3.94 eV, and 3.85 eV with annealing temperatures at 500 °C, 600 °C, and 700 °C, respectively. However, these results contradicted previous work [22], [23], [38], and the optical bandgap obtained was higher than bulk ZnO 3.37 eV [25].…”

“…The band gap values were obtained with different annealing temperatures are 4.10 eV, 3.50 eV, 3.43 eV, and 3.59 eV for as deposited, 500 °C, 600 °C, and 700 °C, respectively. Furthermore, these findings are almost same with the findings of the researchers [22] as the researchers obtained the result of 3.86 eV, 3.69 eV, 3.60 eV, and 3.47 eV for same varied temperature in this work.…”

“…The NiO film showed two prominent peaks at 37.3° and 63.01° in the pattern corresponding to pH 10 after annealing. These peaks correspond to the (1 1 1) and (2 2 0) cubic NiO diffraction planes, respectively, as confirmed by the international centre for diffraction data (ICDD 00-044-1159) [22]. Based on the XRD pattern, it was observed that the highest peak was at 600 °C.…”

The development of low-cost spin coater with wireless IoT control for thin film deposition

“…The resultant spin coater offers a variable spin speed ranging from 300 to 5,000 rpm, controllable through a user-friendly touchscreen interface [5]. In addition to its critical role in semiconductor manufacturing, spin coating holds particular importance in the application of thin films, including cutting-edge materials like perovskites [6], [7]. Thin films, characterized by their nanoscale thickness, find widespread application in various fields, from electronics to optics.…”