ABSTRACT
The incorporation of plasmonic metal nanoparticles (NPs) into the multilayered architecture of perovskite solar cells (PSCs) has been a recurrent strategy to enhance the performance of photovoltaic devices from the early development of this technology. However, the specific photophysical interactions between the metal NPs and the hybrid halide perovskites are still not completely understood. Herein, we investigate the influence of Au NPs on the photoluminescence (PL) signal of a thin layer of the CH3NH3PbI3 hybrid perovskite. Core-shell Au@SiO2 NPs with a tunable thickness of the SiO2 shell were used to adjust the interaction distance between the plasmonic NPs and the perovskite layer. Complete quenching of the PL signal in the presence of the Au NPs is measured together with the gradual recovery of the PL intensity at a thicker thickness of the SiO2 shell. A nanometal surface energy transfer (NSET) model is employed to reasonably fit the experimental quenching efficiency. Thus, the energy transfer deactivation is revealed as a detrimental process occurring in the PSCs since it funnels the photon energy into the non-active excited state of the Au NPs. This work indicates that tuning the distance between the plasmonic NPs and the perovskite materials by a silica shell may be a simple and straightforward strategy for further improving the efficiency of PSCs.
ABSTRACT
A compromise between high power conversion efficiency and long-term stability of hybrid organic-inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and moisture exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35-60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantly delayed with respect to devices without encapsulation when vented continuously with very humid air (RH > 85%). More impressively, when encapsulated solar devices were immersed in liquid water, the photovoltaic performance was not affected at least within the first 60 s. In fact, it has been possible to measure the power conversion efficiency of encapsulated devices under operation in water. The proposed method opens up a new promising strategy to develop stable photovoltaic and photocatalytic perovskite devices.
