Demystifying Complex Quantum Dot Heterostructures Using Photogenerated Charge Carriers

Abstract

The success of heterostructure quantum dots in optoelectronic and photovoltaic applications is based on our understanding of photogenerated charge carrier localization. However, often the actual location of charge carriers in heterostructure semiconductors is quite different from their predicted positions leading to suboptimal results. In this work, photoluminescence of Cu doped heterostructures has been used to study the charge localization of alloys, inverse type I, type II, and quasi type II core/shell structures and graded alloys. Specifically, the adeptness of this method has been assessed over a range of widely studied heterostructures like CdSe/CdS, CdS/CdSe, CdSe/CdTe, ZnCdSe and ZnCdS quantum dots systems by doping them with a small percentage of Cu. The electron and hole localization obtained from this method concurs with the pre-existing understanding in cases that have been explored before, while the internal structure of previously unknown heterostructures have been predicted.

Electrochemical Evaluation of Dopant Energetics and the Modulation of Ultrafast Carrier Dynamics in Cu-Doped CdSe Nanocrystals

“…Doping transition metal ions in a semiconducting nanocrystalline host efficiently introduces new optoelectronic properties resulting from dopant–exciton interaction. − In this regard, Cu-doped semiconducting NCs are promising candidates for light emitting devices and display technologies due to tunability of emission, long radiative lifetimes with high quantum yields, and large Stokes shift. ,− In Cu-doped NCs, a broad tunable dopant photoluminescence (PL) arises from the recombination of delocalized conduction band (CB) electron with the Cu-localized hole. The photophysical properties of Cu-doped NCs have been extensively studied including tunability of the dopant emission, single particle spectroscopy, electronic structure of doped NCs revealed through density functional theory (DFT) calculations, and use of Cu dopant as nanosensor to monitor the optoelectronic properties of NC host. ,− ,− …”

Origin of the Substitution Mechanism for the Binding of Organic Ligands on the Surface of CsPbBr3 Perovskite Nanocubes

“…Colloidal cesium lead halide nanocubes (NCs) became popular in the last couple of years because of their defect-tolerant nature, where surface defects were inefficient to trap charge carriers. − Consequently, these NCs show promise for applications in light-emitting diodes (LEDs), − solar cells, and photodetectors. , To enhance the efficacy of these applications, understanding of both the surface chemistry − and the internal structure − of NCs is essential. Surface chemistry of nanocrystals has been developed extensively for traditional II–VI, III–V, and IV–VI compound semiconductors .…”

Copper Doping in II–VI Semiconductor Nanocrystals: Single-Particle Fluorescence Study

“…Doping Cu into semiconductors introduces a localized intragap energy state, which undergoes charge carrier exchange with the valence band (VB) and conduction band (CB) through radiative as well as nonradiative pathways − and gives rise to new photoluminescence (PL) property at the expense of excitonic PL (also known as band-edge PL). This intragap Cu luminescence center has been extensively studied ,− and has shed light on various electronic properties of the doped nanocrystals (NCs).…”

“…Doping Cu into semiconductors introduces a localized intragap energy state, which undergoes charge carrier exchange with the valence band (VB) and conduction band (CB) through radiative as well as nonradiative pathways − and gives rise to new photoluminescence (PL) property at the expense of excitonic PL (also known as band-edge PL). This intragap Cu luminescence center has been extensively studied ,− and has shed light on various electronic properties of the doped nanocrystals (NCs). While the photogenerated electron (PGE) has been largely accepted to be involved in the Cu-related peak in the PL spectrum, − the origin of the hole is very controversial and has become a “center table subject” for debate among the researchers.…”