Chiral Excitonic Organic Photodiodes for Direct Detection of Circular Polarized Light

Abstract

A facile route to soft matter self-powered bulk heterojunction photodiode detectors sensitive to the circular polarization state of light is shown based on the intrinsic excitonic circular dichroism of the photoactive layer blend. As light detecting materials, enantiopure semiconducting small molecular squaraine derivates of opposite handedness are employed. Via Mueller matrix ellipsometry, the circular dichroism is proven to be of H-type excitonic nature and not originating from mesoscopic structural ordering. Within the green spectral range, the photodiodes convert circular polarized light into a handedness-dependent photocurrent with a maximum dissymmetry factor of ±0.1 corresponding to 5% overall efficiency for the polarization discrimination under short circuit conditions. On the basis of transfer matrix optical simulations, it is rationalized that the optical dissymmetry fully translates into a photocurrent dissymmetry for ease of device design. Thereby, the photodiode's ability to efficiently distinguish between left and right circularly polarized light without the use of external optical elements and voltage bias is demonstrated. This allows a straightforward and sustainable future design of flexible, lightweight, and compact integrated platforms for chiroptical imaging and sensing.

Nanoscale Polarization‐Resolved Surface Photovoltage of a Pleochroic Squaraine Thin Film

“…Most of the light from 500 to 780 nm is anisotropically absorbed in the SQIB layer, but not in the underlying PCBM or ITO/glass. A transfer matrix approach was used to calculate the electric field intensity and the absorption profile within the sample (data not shown) . For both polarization directions, light absorption in the SQIB layer is largest within 10–20 nm from the SQIB:PCBM interface.…”

Polymorphic chiral squaraine crystallites in textured thin films

“…Anilino squaraines are quadrupolar, donor‐acceptor‐donor‐type small molecule semiconductors that are easily accessible via condensations reactions . In the solid, they are characterized by strong intermolecular interactions mediating intense excitonic coupling with visible light, which renders them well suited for light harvesting and detection applications . Here, chiroptical properties such as excitonic circular dichroism (CD) are in the spotlight having its added value in opto‐electronics in view .…”

“…In the solid, they are characterized by strong intermolecular interactions mediating intense excitonic coupling with visible light, which renders them well suited for light harvesting and detection applications . Here, chiroptical properties such as excitonic circular dichroism (CD) are in the spotlight having its added value in opto‐electronics in view . Polymorphism and anisotropic thin film texture, as well as the formation of molecular H‐ and J‐aggregates, are typical features of squaraine dyes.…”

“…Polymorphism and anisotropic thin film texture, as well as the formation of molecular H‐ and J‐aggregates, are typical features of squaraine dyes. Often two or more translationally invariant molecules are present per unit cell enabling a spectrally well‐resolved Davydov splitting of the coupled molecular resonance …”

Building Supramolecular Chirality in Organic Solar Cells Enables High-Performing Circularly Polarized Light Detection

“…The unique polarization state enables CPL to be applied to some cutting-edge science and technology breakthroughs, such as drug screening 5 , quantum optics 6,7 , optical communications 7 and imaging [8][9][10] . An intriguing topic closely associated with these issues is the sensitive discrimination of opposite handedness between l-and r-CPL by electronic devices [11][12][13][14][15][16][17][18] . However, the realization of CPL detection in inorganic photodetectors excessively relies on packaged lters consisting of quarter-wave plates and linear polarizers because of the inherent achiral property of inorganic semiconductors.…”