Inkjet Printing Multicolor Pixelated Quantum Dots on Graphene for Broadband Photodetection

Abstract

Pixelated broadband photoconductors consisting of chemical vapor deposition (CVD) grown graphene on Si/SiO2 and colloidal ZnO and PbS quantum dots (QDs) and FeS2 nanocrystals (NCs) are fabricated by inkjet printing of the QDs and NCs onto predefined graphene channels between Au electrodes. For a comparison, tandem devices with multilayers of QDs were also fabricated on graphene. The optoelectronic performance of these devices was characterized at different wavelengths in the ultraviolet–visible–near-infrared spectra. Specifically, the photoresponsivities are 97.5 A/W (24.4 A/W·V), 7.41 A/W (1.85 A/W·V), and 6.81 A/W (1.70 A/W·V) on the ZnO (340 nm), FeS2 (550 nm), and PbS (900 nm) channels, respectively, which correspond to the external quantum efficiencies (EQE) of 35580%, 1670%, and 940% for the three channels. In addition, the dynamic response of the ZnO-QD/graphene, PbS-QD/graphene, and FeS2-QD/graphene devices are 2 s/29 s, 300 ms/3.2 s, and 204 ms/240 ms for the rise and fall times, respectively, where the ZnO-QD, PbS-QD, and FeS2-QD device channels are measured at wavelengths of 340, 900, and 550 nm, respectively, all at a 1.0 V bias. In contrast, the photoresponsivities are 0.67 and 20.8 A/W for 900 and 340 nm, respectively, for the tandem device and with EQE values of 90% and 7590%, in addition to response times of 12.1 and 40.3 s at 900 nm and no appreciable response time to 340 nm. This result shows that the pixelated photoconductor benefits from direct charge transfer to the graphene channel whereas the tandem devices suffer from inefficient charge transfer between different QD layers that reduces the responsivity and response speed. This low-cost printed pixelated QD/graphene device shows the viability of printed broadband photoconductors compared to more expensive routes of device fabrication, in addition to offering compatibility to current standard complementary metal oxide semiconductor devices.

Localized Surface Plasmon Resonance Enhanced Light Absorption in AuCu/CsPbCl3 Core/Shell Nanocrystals

“…It should be pointed out that stacking PNCs into multilayers may increase light absorption through increased PNC layer thickness, this strategy is however not suitable to highperformance optoelectronics due to charge traps formed at the PNC-PNC junctions in the PNC multilayers, which typically lead to reduced photocurrents and slow photoresponse. [26,27] Exciton-plasmon coupling through introduction of metallic nanostructures to induce localized surface plasmonic resonance (LSPR) near PNCs may provide a resolution to the limited light absorption issue in PNCs. Motivated by this, this work reports the first success in synthesis of AuCu/CsPbCl 3 core/shell PNCs in which an all-inorganic perovskite CsPbCl 3 crystalline shell forms through heteroepitaxy on an LSPR AuCu crystalline core.…”

Quantum Dots and Their Applications: What Lies Ahead?

“…35 Midwavelength IR photoconductive photodetectors with high responsivity were fabricated from Ag 2 Se QDs. 36 Printing techniques were also applied to PbS QD-based devices, such as broadband photoconductors 37 and photodetector arrays. 38 Photodetectors operating in the ultraviolet spectral range have been fabricated using a WS 2 QD−graphene nanocomposite, 39 while phototransistors with balanced photo-detection were obtained based on CsPbBr 3 colloidal QDs and few-layer MoS 2 .…”

“…Midwavelength IR photoconductive photodetectors with high responsivity were fabricated from Ag 2 Se QDs . Printing techniques were also applied to PbS QD-based devices, such as broadband photoconductors and photodetector arrays …”

Nanohybrid Photodetectors

“…More recently, pixelated broadband photodetectors consisting of graphene, colloidal ZnO, FeS 2 , and PbS NCs were reported. [ 156 ] The different colloidal NCs with different wavelength absorption ranges were inkjet printed onto predefined graphene channels embedded in Au electrodes. The pixelated multicolor photodetectors exhibited high photoresponsivities of 97.5, 7.41, and 6.81 A/W on ZnO (340 nm), FeS 2 (550 nm), and PbS (900 nm) channels, respectively, compared with 20.8 A/W (340 nm) and 0.67 A/W (900 nm) for ZnO/FeS 2 /PbS/graphene tandem photodetectors at a voltage of 1.0 V. This cost‐effective printed pixelated NC/graphene photodetectors show the capability of printed broadband optoelectronic devices compared with more expensive routes of device fabrication, in addition to offering compatibility to current CMOS circuit systems.…”