Plasmonic nanomeshes: their ambivalent role as transparent electrodes in organic solar cells

Abstract

In this contribution, the optical losses and gains attributed to periodic nanohole array electrodes in polymer solar cells are systematically studied. For this, thin gold nanomeshes with hexagonally ordered holes and periodicities (P) ranging from 202 nm to 2560 nm are prepared by colloidal lithography. In combination with two different active layer materials (P3HT:PC61BM and PTB7:PC71BM), the optical properties are correlated with the power conversion efficiency (PCE) of the solar cells. A cavity mode is identified at the absorption edge of the active layer material. The resonance wavelength of this cavity mode is hardly defined by the nanomesh periodicity but rather by the absorption of the photoactive layer. This constitutes a fundamental dilemma when using nanomeshes as ITO replacement. The highest plasmonic enhancement requires small periodicities. This is accompanied by an overall low transmittance and high parasitic absorption losses. Consequently, larger periodicities with a less efficient cavity mode, yet lower absorptive losses were found to yield the highest PCE. Nevertheless, ITO-free solar cells reaching ~77% PCE compared to ITO reference devices are fabricated. Concomitantly, the benefits and drawbacks of this transparent nanomesh electrode are identified, which is of high relevance for future ITO replacement strategies.

Mechanotunable Plasmonic Properties of Colloidal Assemblies

“…These nanohole arrays can support SLRs and are typically fabricated by transferring hexagonally ordered arrays of polystyrene particles from an air/water interface onto substrates, followed by etching of the particles before depositing the metal. Stelling et al have systematically examined such silver nanomeshes regarding their plasmonic properties by varying the particle sizes and thereby the size of the holes over a broad range and supporting their results with FDTD simulations . In a more recent publication, Torrisi et al have shown an application for these nanomeshes as an intralayer film between transparent conductive oxides (TCO).…”

Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading

“…where ζ ∈ [0, 1] is the duty cycle, ε m (λ 0 ) is the permittivity of Mo [38], and ε d (λ 0 ) is the permittivity of Al 2 O 3 [33]. Spectrums of real and imaginary parts of the relative permittivity ε(λ 0 )/ε 0 of MgF 2 [31], AZO [33], iZnO [34], CdS [36], Al 2 O 3 [37], and Mo [38] used in our calculations are displayed in Fig. 2.…”

Emerging Novel Metal Electrodes for Photovoltaic Applications

“…Besides the template fabricated through photolithography, the periodic or random arranged microspheres on substrate can also act as the template for the deposition of metal film with micrometer size holes, which allow the penetration of light . Thin film with the formation of cracks inside, in most cases, is normally regarded as poor quality.…”

“…The Au nanomesh induced plasmonic effects has improved the short‐circuit current density ( J SC ) from 7.02 to 14.2 mA cm −2 . As shown in Figure a, the periodicities of the Au nanomesh can be modulated to excite surface plasmon at different resonant wavelengths, which can selectively improve the light absorption of active layer . Figure b is the cross‐sectional SEM image of the representative Au nanomesh incorporated OSCs .…”

“…a) SEM images of plasmonic gold nanohole arrays with the periodicities of 570 and 1040 nm. Reproduced with permission . Copyright 2017, Nature Publishing Group.…”