Rational Molecular Design of π-Extended Thiazolothiazole for High-Performance UV-OPDs Seamlessly Integrated with CMOS

Area of Science:

• Organic electronics
• Photodetector technology
• Materials science

Background:

• Vacuum-deposited organic photodiodes (OPDs) offer advantages like narrowband selectivity but struggle with achieving ultraviolet (UV) selectivity.
• Key challenges include balancing efficient charge transport (strong π-π stacking) with the wide bandgap needed for UV absorption and vacuum deposition (limited π-conjugation).

Purpose of the Study:

• To design and fabricate UV-selective OPDs using a novel molecular strategy.
• To overcome the limitations of existing vacuum-deposited UV-OPDs by tailoring molecular structure.

Main Methods:

• Employed a molecular design strategy using thiazolothiazole (Tz)-based small molecules with controlled planarity and conjugation length.
• Fabricated vacuum-deposited active layers and characterized the resulting OPDs for performance metrics.

Main Results:

• Achieved UV-selective OPDs with wide bandgaps and robust π-π stacking.
• Optimized devices demonstrated high UV selectivity (FWHM: 60 nm), specific detectivity (1.06 × 10¹² Jones), and fast response (50,100 Hz cutoff).
• These results represent the highest performance for vacuum-deposited UV-OPDs to date.

Conclusions:

• The molecular design strategy successfully reconciled competing requirements for UV-selective OPDs.
• Demonstrated seamless integration with CMOS image sensors for multifunctional imaging.
• Provided key molecular insights for advancing UV-selective organic photodetector development.