In recent years, the significant progress of organic-inorganic hybrid perovskite solar cells has surprised the photovoltaic community. Moreover, many other optoelectronic devices have been fabricated using this new generation of materials which makes it more attractive for researchers. Among different physical and chemical synthesis methods, we have taken on a two-step solution-based synthesis procedure to deposit CH3NH3PbI3 with 1.55 eV energy band gap in ambient air condition. Various optoelectrical characterization tools have been used to thoroughly investigate the perovskite film quality. Simulations were carried out using Finite-Difference Time-Domain method (FDTD) for studying light absorption mechanism in perovskite films. Various surface roughness amounts were applied to the simulations to achieve a good consistency between experimental and theoretical absorption curves. This approach can give an insight into how surface roughness effectively impacts on the optical characteristics of the synthesized layer. Moreover, light absorption mechanism has been also investigated which demonstrates how light with a wavelength of more than 540 nm can be transmitted from a 400 nm thick perovskite layer. Simulations also illustrate how surface roughness can help light trapping in the perovskite layer.@en

Metal-assisted etching of silicon in HF/H₂O₂ aqueous solutions has been used to fabricate luminescent silicon nanowires (SiNWs) and porous silicon. The impact of the gold catalyst layer thickness and the etching solution on the morphology of the synthesized nanostructures and the diameter of the obtained nanowires were systematically investigated. Scanning electron microscopy (SEM) analyses reveal that the morphology of the fabricated structures strongly depends on the composition of the solution and the thickness of the catalyst layer. It has been observed that SiNWs are formed in solutions with H₂O₂ ratios (ξ) below 10 %; increasing the H ₂O₂ concentration above this critical value leads to mesoporous (10 % < ξ < 14 %) and macroporous (14 % < ξ < 17 %) structures. Photoluminescence measurements show that SiNWs emit light at about 430 nm. Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) analyses were utilized to determine the origin of the emission in the silicon nanostructures. TEM imaging demonstrates that SiNWs are covered by a thin layer of porous silicon, which is assumed to be responsible for their light emission.

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