Abstract
The recent development of organic polaritonic solar cells, in which sunlight absorbers and photon modes of a resonator are hybridized as a result of their strong coupling, has revealed the potential this interaction offers to control and enhance the performance of these devices. In this approach, the photovoltaic cell is built in such a way that it also behaves as an optical cavity supporting spectrally well-defined resonances, which match the broad absorption bands of the dyes employed. Herein we focus on the experimental and theoretical analysis of the specific spectral and angular optical absorption characteristics of a broadband light harvester, namely a subphthalocyanine, when operating in the ultrastrong coupling regime. We discuss the implications of having a broad distribution of oscillator strengths and demonstrate that rational design of the layered structure is needed to optimize both the spectral and the angular response of the sunlight harvester dye.
Highlights
The recent development of organic polaritonic solar cells, in which sunlight absorbers and photon modes of a resonator are hybridized as a result of their strong coupling, has revealed the potential this interaction offers to control and enhance the performance of these devices
A layered structure made of subphthalocyanine (SubPc)-based thin films, each one performing a different function, was sandwiched between two metal contacts, which played the role of both electrical contacts and mirrors
One specific characteristic of the strong-coupling configuration employed in solar cells is the inhomogeneous character of the electronic transitions involved in the coupling: the absorption bands involved are either excitonic Q-bands, characteristic of porphyrinoids and described by Gouterman’s model,[21,22] which results from the convolution of several HOMO− LUMO transitions, or charge transfer (CT) bands, which are usually even broader
Summary
We analyze the absorption properties of a broadband solar molecular absorber, a perfluorinated SubPc substituted with an ethynylaniline moiety in its axial position (thereafter referred to as SubPc-Et, Figure 1a),[28] embedded in pubs.acs.org/JPCL. A similar analysis performed at different incidence angles allows us to obtain the energy dispersion of both the SubPc-Et (productive) and the metals (parasitic) absorptance, which are plotted as intensity maps in Figures 4d and 4e (results for nonpolarized light, estimated by averaging the experimental results attained for the S and P polarizations at each incidence angle). A rigorous analysis of the effect of the coupling (be it weak, strong, or ultrastrong) of a light harvesting material to metallic cavities should always include an estimation of contributions of the mirrors to the absorption In this case, as it can be concluded from the comparison of Figures 2a and 2b and Figure 4e, optical losses in the mirrors only modify quantitatively, and by a small amount, the experimental polaritonic energy dispersion attained.
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