Integrating an electrically active colloidal quantum dot photodiode with a graphene phototransistor

Abstract

The realization of low-cost photodetectors with high sensitivity, high quantum efficiency, high gain and fast photoresponse in the visible and short-wave infrared remains one of the challenges in optoelectronics. Two classes of photodetectors that have been developed are photodiodes and phototransistors, each of them with specific drawbacks. Here we merge both types into a hybrid photodetector device by integrating a colloidal quantum dot photodiode atop a graphene phototransistor. Our hybrid detector overcomes the limitations of a phototransistor in terms of speed, quantum efficiency and linear dynamic range. We report quantum efficiencies in excess of 70%, gain of 105 and linear dynamic range of 110 dB and 3 dB bandwidth of 1.5 kHz. This constitutes a demonstration of an optoelectronically active device integrated directly atop graphene and paves the way towards a generation of flexible highly performing hybrid two-dimensional (2D)/0D optoelectronics.

High-response hybrid quantum dots- 2D conductor phototransistors: recent progress and perspectives

“…This is confirmed by the data of Ref. [68], where τ ℓ was evaluated as 10 − 4 s and P 0 , as 10 − 4 W/cm 2 (see Figure 9D). Thus, the short photoelectron lifetime substantially increases the characteristic power and the dynamic range of the detector.…”

“…Finally, in Ref. [68], it has been demonstrated that the fieldenhanced charger transfer from PbS QDs to graphene via additional ITO electrode drastically increases the power range (up to 10 − 3 W/cm 2 ), where the responsivity is power independent (see Figure 9D). …”

“…All hybrid phototransistors demonstrated high gain, responsivity, and detectivity but relatively long rise and relaxation times, which changes from several subseconds to dozens of seconds. To accelerate charge transfer between QDs and 2D conductors, in a very recent work [68], Nikitskiy et al employed the device architecture [69] that combines the QD photodiode with transistor. …”

“…In Ref. [68], the PbS colloidal QDs with the exciton peak at 1600 nm allows for extending operation of ITO-QDs-graphene diode-transistor photodetector to 1700-1800-nm wavelength (0.7 eV or 170 THz). Thus, spectral responsivities of hybrid phototransistors are determined by the absorption spectra of QD nanomaterials and can be controlled by QD size.…”

“…In particular, ligands of the amine group are relatively long, and even in the QD nanomaterial [23], (B) [10], and (C) [62]; (D) integrating diode-transistor detector based on graphene with PbS QDs [68].…”