Impact of Specifically Shaped Plasmonic Gold Nanoparticles and a Double Cathode Interfacial Layer on the Performance of Conducting Polymer-Based Photovoltaics

Specifically shaped plasmonic gold nanoparticles (AuNPs) and their combined effect with the double cathode interfacial layer for increasing the power conversion efficiency (PCE) of poly(3-hexylthiophene):(6,6)-phenyl-C61/71-butyric acid methyl ester (P3HT:PC61/71BM)-based polymer solar cells (PSCs) are methodically established. Two diverse donor–acceptor blend polymers, P3HT:PC61BM and P3HT:PC71BM, were used here along with BPhen and BCP as the buffer layers of the conventional LiF:Al cathode contact. Initially, four specifically shaped AuNPs, viz., CTAB capped gold nanorods (AuNRs), gold nanospheres (AuNSs), gold nano-ovals (AuNOs), and gold nanobranches (AuNBs) were separately synthesized and blended along with a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transporting layer to obtain four novel nanoparticle-doped hole injecting layers, and their effect on P3HT:PCBM-based polymer photovoltaic device performance was methodically analyzed. The synthesized nanoparticles were characterized by various characterization techniques, viz., UV–vis absorption study and TEM analysis to confirm their size and shape. The intention of varying the shape of the NPs was to improve the light scattering phenomenon within the polymer solar cell for the generation of higher photocurrent. From the outputs of the fabricated solar cells, it has been found that both types of donor–acceptor polymer blends showed a higher PCE value in the presence of AuNR-modified PEDOT:PSS with bathocuproine (BCP) as an additional buffer layer and LiF–Al combination as a conventional cathode in comparison with bathophenanthroline (BPhen) on the strong basis of better charge transport between BCP–LiF–Al and donor–acceptor blend layers with improved light scattering of the AuNRs at the solar absorption spectrum region compared to AuNSs, AuNOs, and AuNBs. Polymer-based photovoltaic devices with the architecture ITO/PEDOT:PSS+AuNRs/P3HT:PC71BM/BCP–LiF–Al were observed to generate the highest efficiency value of 5.83%, Voc = 0.58 V, Jsc = 15.80 mA/cm2, and FF = 63%, whereas, for the structure ITO/PEDOT:PSS+AuNRs/P3HT:PC61BM/BCP–LiF–Al, the highest solar cell outputs were 5.53%, Voc = 0.58 V, Jsc = 16.28 mA/cm2, and FF = 58%, presenting the best values for unmodified PCBM with P3HT. These results confirm the significant influence of specific shapes of AuNPs to impact the PCE values of donor–acceptor P3HT:PCBM blend-based polymer solar cells in the presence of a double cathode interfacial layer.