Ultrafast Colloidal Quantum Dot Infrared Photodiode

Abstract

Lead sulfide (PbS) colloidal quantum dots (QDs) have received attentions as materials for near-infrared (NIR) photodetection in view of their strong and tunable absorption in the NIR region and room-temperature solution processability. However, the realization of high-speed PbS QD photodetection has been severely hindered by the extremely low carrier mobility (∼10 −5 to 10 −2 cm 2 V −1 s −1 ). Here, an ultrafast PbS QD photodiode fabricated with low mobility QDs (∼10 −3 cm 2 V −1 s −1 ) is demonstrated, which has rise/fall times as short as 0.33 μs at zero voltage bias. The fast response is achieved by engineering resistor−capacitor (RC) time delay and charge transport in the device. The photodiode also has an external quantum efficiency (EQE) exceeding 100% under voltage bias, which is possibly due to the photoconductive gain induced by hole transport layer (HTL). The photoconductive gain combined with low noise current enables high sensitivity with a specific detectivity value up to 3.2 × 10 11 Jones at 1125 nm.

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

“…Ranging between 0.6 and 1.6 µs, these rise and fall times are comparable to some of the fastest mature PbS QDPDs, for which times of a few µs have been reported. [ 48 , 49 , 50 ]…”

Silicon Surface Passivation for Silicon-Colloidal Quantum Dot Heterojunction Photodetectors

“…With the well-passivated Si surface, we then proceeded to build Si:CQD heterojunction photodiodes. The PbS CQDs were synthesized via a hot-injection method according to previous reports 38 (also see the Methods section). The absorption spectrum of the PbS CQD in Figure 3a shows an exciton peak at 1290 nm (see Figure S6 for the transmission electron microscopic (TEM) image).…”

Nanocrystal Quantum Dot Devices: How the Lead Sulfide (PbS) System Teaches Us the Importance of Surfaces

“…This post-synthetic surface engineering leads to high carrier mobility (4×10 -2 cm 2 V -1 s -1 ) and improved device power conversion efficiency. 2) In 2014, Chuang et al [56] showed different ligands can be gained from the development and characterization of PbS nanocrystals and devices will facilitate their use for example in photodiode applications [164,165] or can be applied to the development of other nanocrystal chemistries for solar cells, such as leadhalide perovskites as well as non-toxic, lead-free nanocrystals such as AgBiS 2 , [166] Cu 2 S, [167] or Cu 3 BiS 3 nanocrystals. [168]…”