Narrow-bandwidth organic photodetectors utilizing novel filters
Organic opto-electronic devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs) have several advantages compared to conventional inorganic semiconductors. Their low processing temperature enables an easy integration in different fabrication processes. OLEDs for example are commonly used for novel display applications (Smartphones, TV). OPVs emerge as a promising alternative for solar energy conversion.
So far, organic opto-electronic devices are hardly represented in sensing and imaging applications. One reason is, that often, compatible optical filters are required. Typically, thin film interference filters are used, however, they have a strong angular dependency and are difficult to fabricate. We discovered a new type of optical thin film filters that is inherently compatible to organic opto-electronic devices. With these filters, novel applications in imaging and sensing become possible.
Within the scope of this thesis, these novel optical filters are applied to organic photodetectors (OPDs). OPDs convert a flux of photons into electrical current. For a certain photon energy, or wavelength the yield of this process defines the external quantum efficiency (EQE). Utilizing the novel filters, narrow-bandwidth OPDs can be realized, which are suitable for imaging and spectroscopy. First theoretical calculations predict a full width at half maximum (FWHM) of 35 nm while maintaining a high efficiency. This outperforms state-of-the-art narrow-bandwidth OPDs [1].
The work includes fabrication of novel thin film filter as well as OPDs. Furthermore, the filters are characterized in respect of refractive index, transmission and luminescence, while OPDs are characterized in terms of spectral energy conversion (EQE) and current-voltage characteristics. With the use of optical simulations, the interaction of both components will be optimized, yielding extremely narrow-bandwidth OPDs sensitive for red, green and blue.