Analysis of Carrier Transport in Quantum Dot/Metal‐Oxide Phototransistors via Light‐Mediated Interfacial Modeling

Abstract

Quantum dot (QD) hybrid phototransistors based on high‐mobility channel semiconductors have attracted great interest due to their outstanding photonic characteristics with diverse and broadband optoelectronic functionalities. However, difficulties for precise control of electronic coupling between QD particles and lack of QD/semiconductor interface analysis have limited the use of these platforms into practical optoelectronic applications. Here, the authors report a new strategy to high‐performance phototransistors based on CdSe QD/amorphous oxide semiconductor heterostructures using trap‐reduced chelating chalcometallate surface ligands by optimizing the QD layer thickness and interface engineering to enhance photogenerated charge transfer properties. Furthermore, based on performance parameters extracted from experimental structure and electrical characteristics, Technology Computer‐Aided Design (TCAD) modeling reveals carrier flow between the QDs in the semiconductor layer in agreement with various spectroscopic data. These modeling results indicate that interface engineering of QD with chalcometallate ligand results in very efficient photo‐induced charge transfer characteristics. Thus, high‐performance chalcometallate ligand QD‐based phototransistors are successfully realized with enhanced responsivity (2.12 × 104 A W−1) and photodetectivity (2.74 × 1016 Jones) compared with conventional monodentate ligand functionalized (SCN−) QD‐based devices (8.79 × 103 A W−1 and 8.8 × 1010 Jones, respectively). This is the demonstration of systematic analysis of QD‐based hetero‐structured phototransistors with light‐mediated interfacial physical modeling and electrochemical measurement.

Improvement in Performance and Stability of PbS QD/IGZO Phototransistors Through the Introduction of Ga2O3 Film for Broadband Sensor Applications

“…These results could be attributed to an increased quenching effect and enhanced charge extraction efficiency in the Ga 2 O 3 /PbS QD/IGZO stacks compared with the control PbS QD/IGZO sample. 41 The decay times were calculated using eq 1 based on the TRPL data.…”

“…Such improvements would be reflected in not only the efficiency of carrier transport but also the photodetector performance in the resulting phototransistors. 41,43 Figure 4a−d shows the evolution in transfer characteristics of the PbS QD/IGZO phototransistors without passivation and with Ga 2 O 3 passivation at PO 2 = 0%, 5%, and 10%, respectively, under NIR exposure (λ = 1550 nm) values ranging from 0.1 to 2 mW/cm 2 . The performance metrics of the phototransistor such as R, D*, photosensitivity (PS), and external quantum efficiency (EQE) were obtained using eq 2 through eq 5.…”

“…Compared to the control PbS QD/IGZO sample, substantial reduction in PL intensity and peak broadening was observed for the Ga 2 O 3 /PbS QD/IGZO stacks along with a slight blue shift. These results could be attributed to an increased quenching effect and enhanced charge extraction efficiency in the Ga 2 O 3 /PbS QD/IGZO stacks compared with the control PbS QD/IGZO sample . The decay times were calculated using eq based on the TRPL data. f false( t false) = ∑ i A i exp true( prefix− t τ i true) + K …”

“…This result supported our interpretation that the passivated PbS QD/IGZO stacks had enhanced interconnections within the PbS QD layers and reduced trap densities. Such improvements would be reflected in not only the efficiency of carrier transport but also the photodetector performance in the resulting phototransistors. , …”