Organic photodetectors spectrally matched to optical fiber communication windows

The progress in the field of organic photodetectors has recently led to the development of very fast and efficient devices, but their spectral sensitivity is mainly limited to the visible, without covering the regions of the spectrum of greater interest for telecommunications. One of the major issues when dealing with long wavelength organic photodetectors is the usually poor environmental stability of low bandgap organic semiconductors. A possible exception to this scenario is represented by coordination complexes with organic ligands. We employ as photosensitive materials transition metal dithiolene and dioxolene complexes which combine high thermal and photochemical stabilities with high molar extinction coefficients in the near infrared. Taking advantage of the broad tuning of electronic absorption spectra which can be exerted by changing the oxidation state of the complexes, we develop planar metal-semiconductor-metal photodetectors which are spectrally matched to the optical fiber windows and which can detect light pulses with repetition rates in the range of hundreds of kbit/s. This investigation demonstrates the existence of organic materials of potential telecom interest and that the detection of infrared light pulses is feasible, thus representing a first step toward organic photodetectors for telecommunications.