Towards air-stability of efficient filter-free band-selective organic photodetectors based on bulk heterojunction: avoiding environmental degradation with ALD encapsulation

To detect the band-specific optical signals used in many fields, it is necessary to develop spectrally selective photodetection. For such wavelength-selective photodetection or color discrimination, organic photodetectors (OPDs) can offer significant benefits as low temperature and solution processability, chemical versatility, and specific spectral detection range. However to avoid commonly used filters, the design of a narrowing approach that simultaneously achieves a selective detection range with a bandwidth of less than 50 nm and a spectral response of over 20%, remains a challenge. OPDs based on charge collection narrowing (CCN) principle can provide these features. Herein, we realize filter-free band-selective OPDs based on PM6:PC70BM blends as state-of-the-art. Fine adjustment over a bandwidth of 42 nm to be highly selective at 677 nm with a quantum efficiency of 48.4% under an inverse low bias of -2 V is reached. In addition, using a non-invasive and non-destructive encapsulation technique, we demonstrate that these OPD fully retain their high selective peak after 30 days storage in air.