Perovskite solar cells (PSC) have been identified as a game-changer in the world of photovoltaics. This is owing to their rapid development in performance efficiency, increasing from 3.5% to 25.8% in a decade. Further advantages of PSCs include low fabrication costs and high tunability compared to conventional silicon-based solar cells. This paper reviews existing literature to discuss the structural and fundamental features of PSCs that have resulted in significant performance gains. Key electronic and optical properties include high electron mobility (800 cm²/Vs), long diffusion wavelength (>1 μm), and high absorption coefficient (10⁵ cm⁻¹). Synthesis methods of PSCs are considered, with solution-based manufacturing being the most cost-effective and common industrial method. Furthermore, this review identifies the issues impeding PSCs from large-scale commercialisation and the actions needed to resolve them. The main issue is stability as PSCs are particularly vulnerable to moisture, caused by the inherently weak bonds in the perovskite structure. Scalability of manufacturing is also a big issue as the spin-coating technique used for most laboratory-scale tests is not appropriate for large-scale production. This highlights the need for a transition to manufacturing techniques that are compatible with roll-to-roll processing to achieve high throughput. Finally, this review discusses future innovations, with the development of more environmentally friendly lead-free PSCs and high-efficiency multi-junction cells. Overall, this review provides a critical evaluation of the advances, opportunities and challenges of PSCs.

Printed circuit boards (PCBs) provide a versatile platform for developing point-of-use electrochemical biosensors. Low-cost surface finish, such as electroless nickel immersion gold, on such PCBs offers several advantages over traditional electrochemical sensor substrates, such as cost-effectiveness, scalability, miniaturization, and ease of fabrication. For DNA sensing application of these electrodes, it is necessary to understand the optimal parameter space for error-free operation. In this work, we aim to characterize the double-layer capacitance (DLC) formed at electrode/electrolyte interface for DNA sensing using PCB electrodes. This study investigates the electrochemical behavior of the DLC formed over PCB electrodes in phosphate-buffered saline (PBS) electrolyte using non-Faradaic electrochemical impedance spectroscopy. By varying the electrolyte concentrations ( $\text{1 mM}$ , $\text{5 mM}$ , and $\text{10 mM}$ ) and the ac excitation potential amplitudes (5-100 mV), we analyze DLC formation at the electrode/electrolyte interface. The study examines ionic arrangement transitions at the open circuit potential (OCP), and their impact on DLC retention and distortion. $\text{5 mM}$ PBS electrolyte solution is found to best assist DLC formation as it has the highest capacitive contribution in impedance. In addition, the DLC formation is further examined with dilutions of $\text{20 bp}$ DNA fragments prepared in 1 and $\text{5 mM}$ PBS, ranging from $\text{1 ng}/\upmu \text{l}$ to $\text{20 ng}/\upmu \text{l}$ DNA. The dilutions prepared using $\text{5 mM}$ PBS show sequential change in constant phase element (CPE) parameters of the impedance up to $\text{10 ng}/\upmu \text{l}$ with OCP found to be maintained at a constant value of $\text{40 mV}$ . Higher DNA concentrations show decrease in OCP values, and thus this study presents optimal parameter space for DLC formation with proper ionic arrangement for accurate DNA detection using PCB electrodes.