The photovoltaic effect is the conversion of incident light into useful electricity. Among all solar cell materials, perovskite solar cell (PSC) is considered one of the most prominent and promised candidates in solar cells industries owing to their excellent properties such as cheaper cost, low-temperature chemical processing and fabrication (Ecija et al. 2012; Elumalai et al. 2016), strong absorption of sunlight (Huang et al. 2017), higher mobility of carriers and low rate of non-radiative carrier recombination (Green et al. 2014). In addition, flexible PSCs of different colors can be fabricated effectively and are advantageous to utilize large and wide wavelength ranges. The important parts of PSCs are transparent conductive oxides (FTO, ITO), electron transport layer (ETL), absorber layer (perovskite), hole transport layer (HTL), and the metal contact (Kandjani et al. 2015). Miyasaka's group presented the first-ever report and replaced dye-sensitized solar cells with perovskite (Ch3NH3PbI3) used as liquid sensitizer and achieved a power conversion efficiency (PCE) of 3.8% (Kojima et al. 2009). Kim et al. presented a successful report using perovskite as an active layer, and they also introduced Spiro-MeoTAD as a hole transport layer (HTL) and mesoporous TiO2 as an electron transport layer (ETL). The PCE was achieved at 9.7%, almost three times higher than the one presented in the previous report (Kim et al. 2012). Moreover, PCE of around 22.1% has been investigated for PSCs and is highly expected to jump over 30% (Yang et al. 2017). The optimization of different parameters used in PSCs has become practicable by the rapid efficiency improvements. Each component has its role in improving optical absorption, PCEs, and stability. For instance, the perovskite layer thickness is a dominant factor that extensively affects the absorption of light and the charge separation in HTL and ETL, respectively (Liu et al. 2014). The thin layer of perovskite has not the capability to utilize more optical beams, but on the other hand, it provides a good pathway for charge separation. To resolve this hindrance an alternative solution is needed to enhance optical absorption and improve PSCs device performance without increasing the thickness of the perovskite absorber layer. In such circumstances, the surface plasmon resonance effect is one of the best solutions that utilize metal at the nanoscale embedded in PSCs; when the incoming light from the sun strikes the metal nanoparticle inside the absorber layer; as a result, electrons start shining on the surface of metals, such phenomenon of collectively shining of electrons on the surface of the metal is called localized surface plasmon resonance (LSPR) and thus enable the solar cells to harvest more light. These LSPRs also provide a strong electromagnetic field that leads to enhanced scattering cross-sections and extinction cross-sections for larger atoms (Atwater and Polman 2011). The effect of LSPR has extensively been studied in many photovoltaic devices besides PSCs, such as silicon-based solar cells (Derkacs et al. 2006; Tabrizi and Pahlavan 2020), dye-sensitized solar cells (DSSC) (Brown et al. 2011), and organic solar cells (OSC) (Vangelidis et al. 2018). Zhang et al. first investigated the plasmonic effect in PSCs using metal nanoparticles (NPs) and enhanced PCE to 9.5% as compared to controlled devices (8.4%) (Zhang et al. 2013). Furasova et al. studied the effect of silicon NPs in PSCs that optimize the PCE up to 18.8% compared to the controlled device without NPs at 17.7% (Furasova et al. 2018). Batmunkh et al. reported the influence of gold nanostars on mesoporous TiO2 photoanode in PSCs; they observed the PCE increased from 15.19–17.72%. Moreover, enhanced optical absorption and reduced charged recombination were also investigated (Batmunkh et al. 2017). Aeineh et al. introduced multifunctional Au@SiO2 core-shell in PSCs and thus improved the device performance because of the plasmonic effect (Aeineh et al. 2017). The Au@SiO2 in PSCs is also capable of improved device stability. The stability is due to the SiO2 coating that acts as a shield and protects Au and the perovskite layer. However, a big gap still exists in wisely utilizing the plasmonic effect of nanoparticles with various geometries in PSCs structure. These plasmonic nanoparticles can dramatically change the performance of PSCs in terms of absorption, scattering, efficiency, and stability. Moreover, LSPR caused by these nanoparticles depends on the shape, size, and dielectric function procured by the embedded nanoparticles (Khan et al. 2019; Sui et al. 2019; Tabrizi et al. 2021).
In this paper, we performed the optical simulation of embedded Au NPs with different radii (g), Au@TiO2, and Au@SiO2 with different shell thicknesses (Stk) in the absorber layer of PSC in the wavelength range, i.e., 300–800 nm. The plasmonic effect and the corresponding enhancement in the UV-Vis spectrum were systemically observed for each scheme by tailoring the radius (g) of Au NPs and shell thickness (Stk). Then we further calculated the bandgap energy for each geometry (Au NPs, Au@TiO2, and Au@SiO2 modified inside the perovskite layer with the help of Tauc’s curve. In addition, we finally compared all the results and investigated that the overall optical enhancement in PSC is dedicated to Au@TiO2 as compared to simple Au NPs and Au@SiO2, thus providing a useful track for enhancement and improved stability of PSCs.