Light Absorption Enhancement in Semiconductor Chaotic Nanowire Arrays: Transparent Solar Cell and Image Sensor Application

Abstract

Chaotic behaviours were rst recognized in the early twentieth century while attempting to understand the three-body problems. After chaos was accepted as one of the intrinsic properties of nature, plenty of issues related to quantum properties in classically chaotic systems have been raised and resolved. Through intensive eorts in the eld to unveil this quantum-classical correspondence in chaotic systems, it was revealed that resonance spectra in chaotic systems are very irregular and complicated compared to those in non-chaotic systems. This spectral complexity comes from the fact that as a regular system is gradually perturbed into a chaotic one, mode splittings, breaking of degeneracies, and avoided crossings take place in resonance dynamics. Motivated by these mechanisms, we show that light absorption in chaotic nanowires in an array is remarkably enhanced under the condition of a chaotic wire cross-section. According to our results, this enhancement is proportional to the number of absorption modes, which emerge as the deformation of cross-section increases. We numerically verify the light absorption enhancement by using nite-dierence time-domain simulations and show that the increase in the number of modes is caused by mode splittings and avoided crossings. The light absorption enhancement is experimentally demonstrated by using fabricated samples of freestanding Si-nanowire PDMS composites. Our results are applicable not only to transparent solar cells but also to a CMOS image sensors to maximize absorption efficiency.