Postdeposition Ligand Exchange Allows Tuning the Transport Properties of Large‐Scale CuInSe₂ Quantum Dot Solids

Abstract

Colloidal quantum dots assembled into quantum dot solids usually suffer from poor conductivity. The most common charge transport mechanism through the solid is hopping transport where the hopping probability depends on the barrier type (stabilizing/connecting ligand molecule) and the interparticle distance. It is demonstrated that the electronic structure of the ligand molecule strongly alters the transport behavior through CuInSe2 quantum dot solids. Transport measurements and optical‐pump terahertz‐probe experiments after a ligand exchange to fully conjugated molecules show an increase of the conductivity by orders of magnitude, as well as a change of the hopping transport mechanism. This change is not due to a reduced interparticle distance, but the electronic structure: the obtained frequency‐dependent complex conductivities point toward an efficient hole transport enabled by an alignment of the quantum dot valence bands and ligand states.

InAs Nanocrystals with Robust p‐Type Doping

“…[21][22][23][24] The complexities in doping SC NCs are amplified by the possible differences in behavior of the isolated individual NCs, versus their characteristics in a working NC array in an electronically active device, where modifications of the surface chemistry are essential for effective interconnection to enable electrical transport among the nanocrystals. [25][26][27] Such surface modifications often affect the doping state and even the nature of doping on the level of the NC array. [26,[28][29][30][31][32] Indeed, "remote doping", through binding of electron donating groups, is a successful approach to electronically dope the NCs.…”

“…[25][26][27] Such surface modifications often affect the doping state and even the nature of doping on the level of the NC array. [26,[28][29][30][31][32] Indeed, "remote doping", through binding of electron donating groups, is a successful approach to electronically dope the NCs. [1,[33][34][35][36] On the other hand, this very same process often limits the ability to generate stable n-or -p-type NCs with controlled doping levels and tailored surface chemistry in the array, thus calling for utilization of impurity doping.…”

Double Active Layers Constructed with Halide Perovskite and Quantum Dots for Broadband Photodetection

“…[ 10–12 ] Colloidal CuInSe 2 (CISe) QD with narrow bandgap is considered a candidate for broadband response photodetector because of its high absorption coefficient (≈10 5 cm −1 ), superior stability, and broadband response (UV to near‐infrared). [ 13–18 ] However, choosing an appropriate charge transport layer and preparing a sufficiently thick active layer are the challenges for CISe QD‐based photodetectors. These problems lead to an unsatisfactory response of CISe QD‐based photodetectors in the visible light region compared to traditional detectors.…”

In4Pb5.5Sb5S19: A Stable Quaternary Chalcogenide with Low Thermal Conductivity

“…The chemical formula obtained by resolving the single-crystal diffraction data was In 4.5 Pb 4.5 Sb 5 S 19 , which has a problem of charge balance with a positive charge of 37.5 and a negative charge of −38. Therefore, we used a starting elemental ratio of In 4.5 Pb 4.5 Sb 5 S 19 (1) to attempt to obtain pure phase and chargebalanced samples with the elemental ratios around the SXRD resolved result , and we also tried: In 5 Pb 4 Sb 5 S 19 (2), In 4.5 Pb 4 Sb 5.5 S 19 (3), and In 4.5 Pb 4.5 Sb 5 S 18.8 (4). All the synthesis was conducted under the same conditions for comparison purposes.…”

“…In recent years, several star chalcogen compounds have been synthesized. For example, CdTe and CuInSe 2 cannot be ignored in the field of thin-film solar photovoltaics, , SnSe and PbTe are well-known materials in the field of thermoelectricity, , CdHgTe plays an indispensable part in night-vision cameras, and GeSbTe has outstanding performance in storage . Chalcogenides also play a critical role in current cutting-edge materials research fields, including photoelectric information conversion, nonlinear optics, , radiation detectors, optical information storage, thermoelectric energy conversion, , catalysis, topological insulators, unconventional superconductivity, and solar cells. , …”