Synergetic Near- and Far-Field Plasmonic Effects for Optimal All-Perovskite Tandem Solar Cells with Maximized Infrared Absorption

Abstract

The efficiency and reliability of perovskite solar cells have rapidly increased in conjunction with the proposition of advanced single-junction and multi-junction designs that allow light harvesting to be maximized. However, Sn-based compositions required for optimized all-perovskite tandem devices have reduced absorption coefficients, as opposed to pure Pb perovskites. To overcome this, we investigate near- and far-field plasmonic effects to locally enhance the light absorption of infrared photons. Through optimization of the metal type, particle size, and volume concentration, we maximize effective light harvesting while minimizing parasitic absorption in all-perovskite tandem devices. Interestingly, incorporating 240 nm silver particles into the Pb-Sn perovskite layer with a volume concentration of 3.1% indicates an absolute power conversion efficiency enhancement of 2% in the tandem system. We present a promising avenue for experimentalists to realize ultrathin all-perovskite tandem devices with optimized charge carrier collection, diminishing the weight and the use of Pb.

Figure 1

(a) Single-junction solar cell architecture employed for the simulations. (b) Real and (c) imaginary components of the refractive indices for various NGB Pb–Sn perovskites, as reported in the literature. Simulations are performed using these perovskites compositions. (d) Mean calculated photocurrents vs perovskite film thickness. The top halo shows the total current using the entire AM1.5 spectrum, and the bottom one considers only infrared photons reaching the rear subcell in a tandem configuration (i.e., wavelengths from 750 nm onward).

Figure 2

(a) Scheme of the single-junction plasmonic solar cell system employed in the simulations. We consider a glass/ITO (100 nm)/PEDOT (50 nm)/NBG perovskite (700 nm)/C60 (20 nm)/BCP (10 nm)/gold (100 nm) architecture in which metallic spheres (i.e., silver, gold, and copper) are placed in the midplane of the perovskite layer. Both the size and the volume filling concentrations of the particles are varied to produce the optimal performance. (b) Highest calculated currents for different radii and concentrations.

Figure 3

Enhancement of the performance of a single-junction solar cell with a glass/ITO (100 nm)/PEDOT (50 nm)/NBG perovskite (700 nm)/C60 (20 nm)/BCP (10 nm)/gold (100 nm) architecture through plasmonic effects. (a) Total absorptance spectrum of the reference system (blue) compared with that of the record system (orange) incorporating Ag NPs with an R of 118 nm and a VFC of 2.8%. The ratio of the productive absorptances (i.e., those considering only the photons absorbed by the perovskite material) is also displayed (green), demonstrating a plasmon resonance and a considerable absorption enhancement at λ >750 nm. Differential absorption per unit of volume profiles depicted at (b) λ = 916 and (c) λ = 1038 nm. Reference (right) and record (left) systems are compared. The images show an absorption enhancement where the plasmonically induced multipolar resonance couples the interferential patterns. (d) Current generation calculated over increasing concentric volumes around the Ag sphere. Currents are calculated using only λ >900 nm photons, a regime in which the plasmonic enhancement is more intense. The observed change in the curve slope is attributed to the vanishing near-filed enhancement. Hence, it is estimated that 25% of the enhancement is due to near-field effects, in contrast to far-field (scattering) gain.

Figure 4

(a) Optimization of the sizes and volume filling concentrations of Ag NPs embedded in 700 nm thick NBG perovskites for tandem devices, with a variable thickness of the WBG layer between 340 and 350 nm. (b) Record plasmonic tandem system (R = 120 nm, and VFC = 3.1%) compared to a reference tandem device. The photogenerated currents in each subcell are plotted against the thickness of the WBG perovskite, showing the fulfilment of current matching conditions. (c) Productive absorptance of both reference (dashed lines) and record (solid lines) tandem devices. WBG layer (blue lines) and NBG layer (red lines) absorptance contributions are also depicted.