# Recent Advances in Black Silicon Surface Modification for Enhanced Light Trapping in Photodetectors
## 2 Wet Methods for Black Silicon Fabrication
### Electrochemical Etching
\begin{table}
\begin{tabular}{c c c c} \hline
**Objectives** & **Method** & **Findings** & **Ref.** \\ \hline Enhance efficiency of multi-crystalline BSi & \multirow{4}{*}{MACE (Ag)} & Significantly increased efficiency and optical performance in multi-crystalline BSi solar cells, demonstrating the effectiveness of MACE in enhancing PV cell capabilities. & [24] \\ Investigate etching time effects BSi absorption & \multirow{4}{*}{MACE (Ag)} & Identifying optimal etching durations resulted in a significant reduction in broadband reflectance and a considerable enhancement in absorption efficiency, underscoring the essential influence of etching time on optimizing the optical performance of BSi. & [25] \\ Optimize etching time and study Ag concentration effects & \multirow{4}{*}{MACE (Ag)} & Enhanced broadband light absorption achieved through careful optimization of etching times and silver concentrations, resulting in significant improvements in BSi optical efficiency. & [26; 27] \\ Develop various BSi texturizations and study MACE parameters’ effects. & \multirow{4}{*}{MACE (Ag)} & Development of varied texturizations, including nano-pyramidal and nano-grass structures, improved antireflective properties and overall efficiency of BSi. Adjustments in MACE parameters led to optimized optical properties. & [44; 45; 46; 47; 48; 49] \\ Investigate Ag film thickness effect & \multirow{4}{*}{MACE (Ag)} & Varying the Ag film thickness critically affects BSi optical and morphological properties. Temperature control during etching influenced the formation of large, inverted pyramids, optimizing light trapping on Si surface. & [28; 29] \\ Achieve high efficiency in Si solar cells with BSi. & \multirow{4}{*}{MACE (Ag)} & Creation of hierarchical BSi textures resulted in ultra-low reflectance and omnidirectional light-trapping capabilities, leading to improvements in the c-Si optical properties. & [50] \\ Study Cu-assisted chemical etching and regulate surface texturization & \multirow{4}{*}{MACE (Cu)} & Cu-assisted chemical etching yielded uniform low-reflectance BSi and diverse texturized surfaces, significantly improving the antireflective performance and overall efficiency of Si solar cells. & [31; 32] \\ Study Ni-assisted chemical etching impact on reflection. & \multirow{4}{*}{MACE (Ni)} & The use of Ni-assisted chemical etching effectively minimized reflectance across UV, visible, and infrared spectrums, demonstrating its effectiveness in creating highly efficient light absorbing BSi films. & [33] \\ Study catalyst thickness and annealing effects & \multirow{4}{*}{MACE (Al)} & Investigations into the impact of Al catalyst thickness and annealing on BSi revealed that these factors critically influence surface morphology and reflectivity, leading to optimal conditions for enhanced light absorption suitable for PV applications. & [35; 36; 37] \\ Investigate morphological properties & \multirow{4}{*}{KOH} & The etching process created BSi surfaces with significantly reduced reflectance and high conductivity, thereby enhancing the overall efficiency and performance of solar cells. Optimization of these processes was crucial for improved solar cell applications. & [38; 39] \\ Study optical properties of Si & Electro-chemical & Porous Si photonic crystals exhibited strong light scattering effects and low reflectance, enhancing their utility in photonic applications. & [40; 41] \\ Study optical properties of Si & \multirow{4}{*}{Electro-chemical } & \multirow{4}{*}{Porous Si photonic crystals exhibited strong light scattering effects and low reflectance, enhancing their utility in photonic applications.} & [40; 41] \\ Photonic crystals & & & \\ \hline \end{tabular}
\end{table} 
Table 1: A summary of the recent work in surface modification of BSi by using wet chemical etching for light-trapping applications in optical devices.