Just over a decade, perovskite solar cells (PSCs) have been emerged as a next‐generation photovoltaic technology due to their skyrocketing power conversion efficiency (PCE), low cost, and easy manufacturing techniques compared to Si solar cells. Several methods and procedures have been developed to fabricate high‐quality perovskite films to improve the scalability and commercialize PSCs. Recently, several printing technologies such as blade‐coating, slot‐die coating, spray coating, flexographic printing, gravure printing, screen printing, and inkjet printing have been found to be very effective in controlling film formation and improving the PCE of over 21%. This review summarizes the intensive research efforts given for these printing techniques to scale up the perovskite films as well as the hole transport layer (HTL), the electron transport layer (ETL), and electrodes for PSCs. In the end, this review presents a description of the future research scope to overcome the challenges being faced in the printing techniques for the commercialization of PSCs.

The achievement of H₂ detection, up to 25 ppm, at room temperature using sulfur-treated, platinum (Pt)-decorated porous GaN is reported in this study. This achievement is attributed to the large lateral pore size, Pt catalyst, and surface treatment using organic sulfide. The performance of H₂-gas sensors is studied as a function of the operating temperature by providing an adsorption activation energy of 22 meV at 30 ppm H₂, confirming the higher sensitivity of the sulfide-treated Pt–porous GaN sensor. Furthermore, the sensing response of the sulfide-treated Pt–porous GaN gas sensor increases with the increase in porosity (surface-to-volume ratio) and pore radii. Using the Knudsen diffusion–surface reaction equation, the H₂ gas concentration profile is simulated and fitted within the porous GaN layer, revealing that H₂ diffusion is limited by small pore radii because of its low diffusion rate. The simulated gas sensor responses to H₂ versus the pore diameter show the same trend as observed for the experimental data. The sulfide-treated Pt–porous GaN sensor achieves ultrasensitive H₂ detection at room temperature for 125 nm pore radii.

Herein, we report on the studies of GaN nanowires (GaN NWs) prepared via a metal-assisted photochemical electroless etching method with Pt as the catalyst. It has been found that etching time greatly influences the growth of GaN NWs. The density and the length of nanowires increased with longer etching time, and excellent substrate coverage was observed. The average nanowire width and length are around 35 nm and 10 μm, respectively. Transmission electron microscopy (TEM) shows a single-crystalline wurtzite structure and is confirmed by X-ray measurements. The synthesis mechanism of GaN NWs using the metal-assisted photochemical electroless etching method was presented. Photoluminescence (PL) measurements of GaN NWs show red-shift PL peaks compared to the as-grown sample associated with the relaxation of compressive stress. Furthermore, a shift of the E₂ peak to the lower frequency in the Raman spectra for the samples etched for a longer time confirms such a stress relaxation. Based on Raman measurements, the compressive stress σ_xx and the residual strain ε_xx were evaluated to be 0.23 GPa and 2.6 × 10⁻⁴, respectively. GaN NW synthesis using a low cost method might be used for the fabrication of power optoelectronic devices and gas sensors.