Pushing Colloidal Limits: ∼200 nm InAs Colloidal Quantum Nanorods for Extended Shortwave Infrared Photodetection

InAs colloidal quantum dots (CQDs) are promising for shortwave infrared (SWIR) optoelectronics, due to their size-tunable optical properties, compatibility with CMOS technology, and compliance with the RoHS directive. However, increasing CQD size to achieve extended SWIR (eSWIR) bandgaps and improving charge transport often compromises colloidal stability. Ultralong InAs colloidal quantum nanorods (CQNRs) were synthesized through chemical control using lithium bis(trimethylsilyl)amide (LiN(Si(CH3)3)2), which promotes their elongation, enabling the synthesis of nanorods up to ∼200 nm in length. Transitioning from spherical QDs to nanorods allows size extension without inducing aggregation or precipitation. The resulting CQNRs exhibit excellent colloidal stability and absorption up to 2000 nm in the eSWIR region. Photodiodes fabricated from these CQNRs exhibit very low dark current (6 μA cm-2) and high external quantum efficiency (10.6%), attributed to enhanced percolation pathways with reduced hopping resistance, consistent with four-dimensional scanning transmission electron microscopy and lateral transport measurements. Ultralong, colloidally stable InAs CQNRs combine extended eSWIR absorption with efficient charge transport, making them suitable for environmentally compliant large CQDs in next-generation high-performance eSWIR optoelectronic devices.