In this paper, the light absorption in the active layer of polymer solar cells (OPV) by using plasmonic nanocrystals with a
hexagonal lattice structure is investigated. To study the relationship between the performance of the OPV solar cell and its
active layer, a three-dimensional model of its morphology is utilized. Therefore, the three-dimensional (3D) finite-difference
time-domain method and Lumerical software were used to measure the field distribution and light absorption in the active
layer in terms of wavelength. OPV solar cells with bilayer and bulk heterojunction structured cells were designed using
hexagonal lattice crystals with plasmonic nanoparticles, as well as core–shell geometry to govern a design to optimize light
trapping in the active layer. The parameters of shape, material, periodicity, size, and the thickness of the active layer as a
function of wavelength in OPV solar cells have been investigated. A very thin active layer and an ultra-thin shell were used
to achieve the highest increase in optical absorption. The strong alternating electromagnetic field around the core–shell
plasmonic nanoparticles resulting from the localized surface plasmon resonance (LSPR) suggested by the Ag plasmonic
nanocrystals increased the intrinsic optical absorption in the active layer poly(3-hexylthiophene):phenyl-C61-butyric acid
methyl ester (P3HT:PCBM). Based on the photovoltaic results, the short circuit current ranged from 19.7 to 26.7 mA/cm2.