On the Origin of the Intrinsic Detectivity Limits of Near-Infrared Organic Photodetectors

Organic photodetectors (OPDs) with a performance comparable to that of conventional inorganic ones have recently been demonstrated for the visible regime.^[1] However, near-infrared photodetection at a high detectivity has been proven to be more challenging and, to date, the true potential of organic semiconductors in this spectral range (800–2500 nm) remains largely unexplored. We have recently shown that the main factor limiting the specific detectivity is non-radiative recombination, which is also known to be the main contributor to open-circuit voltage losses in organic photovoltaics.^[2] Based on this finding we concluded that OPDs have the potential to be a useful technology up to 2 μm, given that high external quantum efficiencies can be maintained at these low photon energies. To further elaborate on the fundamentals defining these limitations, a next-generation of ‘defect-free’ organic semiconductors is synthesized. This allows us to investigate the influence of material imperfections (end-capping, homocoupling defects, and other impurities) on the material properties and device performance. In this contribution, we give an overview of the synthetic approaches applied and the latest organic semiconductors for high performance NIR OPDs, approaching their intrinsic limits.<br/><br/>[1] N. Li <i>et al.</i>, <i>Mater.</i> <i>Sci. Eng.</i>, <b>146</b>, 100643 (2021)<br/>[2] S. Gielen <i>et al.</i>, <i>Adv. Mater.</i>, <b>32</b>, 2003818 (2020)