Investigation of optical and mechanical performance of inverted pyramid based ultrathin flexible c-Si solar cell for potential application on curved surface.

• Size control of IPs from sub-micro to micro scale was achieved by varying ρ values. • 40 µm random INPs cell achieved 34.8 mA/cm2 current density and 17.44% efficiency. • Superior mechanical performance was proved on INPs based 40 µm c -Si. • Quasi-omnidirectional characteristics of INPs was found between 0° and 60°. • Quasi-omnidirectional performance of INPs was demonstrated by FDTD simulation. Flexible ultrathin c -Si (U-Si) solar cell is widely researched for its potential usage in places with various shapes and sizes. However, light incident angle (θ) varies with positions on the same cell accompanied with the easy crack of cell due to surface textures when the U-Si cell is under bending. Therefore, the fabrication of efficient antireflectance structures with both quasi-omnidirectional performance and superior mechanical performance is greatly required. Here, size control of inverted pyramid (IP) from nano to micro scale as antireflectance structures is realized by altering ρ ([HF]/[HF] + [H 2 O 2 ]) values at room temperature. The IP is obtained through the nanostructure rebuilding (NSR) treatment of Ag assisted chemical etched nanostructures. In comprehensive consideration of optical and mechanical performances, IP-60 (ρ = 60%) textured 40 µm U-Si cell is successfully fabricated with a short-current density of 34.8 mA/cm2 and energy-conversion efficiency of 17.44%, showing an 0.2 mA/cm2 and 0.13% improvement respectively compared with that of the micro pyramids (MP) based one. Moreover, the quasi-omnidirectional characteristics of IP-60 based 40 μm cell over 0–60° is demonstrated by experiment and simulation. The above finding makes it possible to broaden the application scope of U-Si cells into some new areas like stratospheric airships and wearable electronics. [ABSTRACT FROM AUTHOR]