Broadband Enhancement of PbS Quantum Dot Solar Cells by the Synergistic Effect of Plasmonic Gold Nanobipyramids and Nanospheres

For the first time, the plasmonic gold bipyramids (Au BPs) are introduced to the PbS colloidal quantum dot (CQD) solar cells for improved infrared light harvesting. The localized surface plasmon resonance peaks of Au BPs matches perfectly with the absorption peaks of conventional PbS CQDs. Owing to the geometrical novelty of Au BPs, they exhibit significantly stronger far-field scattering effect and near-field enhancement than conventional plasmonic Au nanospheres (NSs). Consequently, device open-circuit voltage (V-oc) and short-circuit current (J(sc)) are simultaneously enhanced, while plasmonic photovoltaic devices based on Au NSs only achieve improved J(sc). The different effects and working mechanisms of these two Au nanoparticles are systematically investigated. Moreover, to realize effective broadband light harvesting, Au BPs and Au NSs are used together to simultaneously enhance the device optical and electrical properties. As a result, a significantly increased power conversion efficiency (PCE) of 9.58% is obtained compared to the PCE of 8.09% for the control devices due to the synergistic effect of the two plasmonic Au nanoparticles. Thus, this work reveals the intriguing plasmonic effect of Au BPs in CQD solar cells and may provide insight into the future plasmonic enhancement for solution-processed new-generation solar cells.