Organic solar cells having plasmonic nanostructures in different solar cell regions for enhancement of photovoltaic characteristics

Abstract This paper presents the improved photovoltaic characteristics of organic solar cells (OSCs) consisting of low band gap (LBG) active medium and a combination of plasmonic nanostructures embedded in the cathode buffer layer (CBL) and on the upper surface of the bottom silver (Ag) layer of the OSCs. A combination of a 2-dimensional (2D) array of plasmonic nanostructures such as Ag nano-discs (Ag-NDs) present in the CBL of the OSC with a 2D array of either Ag nano-rings (Ag-NRs), Ag nano-discs (Ag-NDs), or Ag nano-hemispheres (Ag-HSs) above the bottom Ag layer of the OSCs, was employed for achieving enhanced performance of the OSCs. Finite-difference time-domain (FDTD) simulations were used to analyze the photon absorption ( A(λ) ), short circuit current density (J SC ), and power conversion efficiency (PCE) of OSCs containing the plasmonic nanostructures. The results of our FDTD simulations demonstrate that these bulk heterojunction OSCs containing Ag-NDs arrays in the CBL primarily increase the A( λ ) in the 650–900 nm spectral regime. On the other hand, our FDTD simulations also demonstrate that 2D arrays of Ag-NDs in the CBL in a combination with 2D arrays of either Ag-NRs, Ag-NDs, or Ag-HSs at bottom of the cells increase the light trapping in the visible and the NIR spectral region, thereby significantly increasing the J SC and PCE of the proposed OSCs. It is observed that while the inclusion of structures consisting of Ag-NDs array in the CBL in a combination with Ag-HSs array at bottom of the cells lead to enhancements in J SC and PCE of 40.36% and 40.36%, respectively, compared to a planar OSC, these enhancement values are only 32.22% and 32.1%, respectively, when only Ag-NDs are present only in the CBL. Hence, a combined structure of Ag-NDs array in the CBL and Ag nanoparticle array at the bottom of the OSC leads to an enhanced J SC and PCE compared to those in a planar OSC or to those when only the NDs are embedded only in the CBL.