Colloidal III–V Quantum Dot Photodiodes for Short‐Wave Infrared Photodetection

Short‐wave infrared (SWIR) image sensors based on colloidal quantum dots (QDs) are characterized by low cost, small pixel pitch, and spectral tunability. Adoption of QD‐SWIR imagers is, however, hampered by a reliance on restricted elements such as Pb and Hg. Here, QD photodiodes, the central element of a QD image sensor, made from non‐restricted In(As,P) QDs that operate at wavelengths up to 1400 nm are demonstrated. Three different In(As,P) QD batches that are made using a scalable, one‐size‐one‐batch reaction and feature a band‐edge absorption at 1140, 1270, and 1400 nm are implemented. These QDs are post‐processed to obtain In(As,P) nanocolloids stabilized by short‐chain ligands, from which semiconducting films of n‐In(As,P) are formed through spincoating. For all three sizes, sandwiching such films between p‐NiO as the hole transport layer and Nb:TiO2 as the electron transport layer yields In(As,P) QD photodiodes that exhibit best internal quantum efficiencies at the QD band gap of 46±5% and are sensitive for SWIR light up to 1400 nm. A complete process flow to form photodiode stacks sensitive for short‐wave infrared (SWIR) light based on non‐restricted In(As,P) quantum dots (QDs) is proposed. Films made of semiconducting n‐In(As,P) QDs inks, formulated through apolar/polar QD phase transfer, form a rectifying junction with p‐NiO that is photosensitive beyond 1400 nm. This result highlights the prospect of printable SWIR opto‐electronics based on InAs QDs.