High-Performance Polymer Solar Cells Enabled by Copper Nanoparticles-Induced Plasmon Resonance Enhancement

The surface plasmon resonance (SPR) effect based on noble metal nanoparticles (NPs) such as gold(Au) and silver(Ag) has been widely investigated and demonstrated to be a breakthrough technology to further improve the power conversion efficiency (PCE) of polymer solar cells (PSCs). Herein, diameter controlled copper (Cu) NPs were intentionally introduced into an anode buffer layer of tungsten trioxide (WO3) by the thermally evaporating method, structuring a light trapping center to enhance light absorption of PSCs. The big difference of surface energy between WO3 and Cu can induce the growth process of Cu NPs from nucleation to isolated island by controlling evaporating thickness, yielding multiple SPR centers to radiate the electromagnetic wave toward the active layer. The steady-state photoluminescence (PL) results provide direct evidence that Cu NPs-induced SPR effect can effectively enhance light absorption of the active layer at visible wavelength, leading to a significant improvement of the short current density (J(sc)) by 35.3% and PCE by 37.2% for devices with 3 nm Cu. Encouragingly, the inclusion of Cu NPs simultaneously decreases device resistance determined by complex impedance spectra. We believe the low-cost, simple-fabricated evaporating method combined with SPR enhancement can pave the way to high-performance PSCs.