Light‐trapping and spectral modulation to increase the conversion efficiency of triple‐junction GaAs solar cells using antireflective coating comprising a periodic array of cone‐shaped TiO 2 structures

Abstract

This study sought to increase the conversion efficiency of triple-junction GaAs solar cells via spectral light trapping through the application of a uniform TiO2 layer with an antireflective coating (ARC) comprising a periodic array of cone-shaped TiO2 structures. The cone-shaped TiO2 ARC structures were fabricated using a mask of polystyrene spheres (PS) of various diameters (600, 700, and 800 nm). This surface modification was meant to match external quantum efficiency (EQE) response and reflectance spectra in order to modulate the light-trapping effects. In experiments, forward light scattering and reduced reflectivity were shown to improve the EQE response of the cells to beyond that of the cell with a uniform layer of TiO2. The average weighted EQE (EQEW) values of the cell with the proposed ARC (PS: 600 nm) exceeded that of cells with larger surface structure (PS: 700 or 800 nm). These modifications were also shown to increase short-circuit current-density (JSC) and conversion efficiency (η), as confirmed by photovoltaic current-voltage measurements under AM 1.5G illumination. The cone-shaped ARC structures also increased the acceptance angle and electrical output under solar illumination of a given duration. Compared to the reference cell, the cell with 600-nm structures enhanced the EQEW by an impressive 40.26% (from 48.88% to 68.56%), JSC by 20.55% (from 9.73 to 11.73 mA/cm2), and η by 20.59% (from 20.98% to 25.30%).