Passivating ligand and solvent contributions to the electronic properties of semiconductor nanocrystals.

نویسندگان

  • Sean A Fischer
  • Angela M Crotty
  • Svetlana V Kilina
  • Sergei A Ivanov
  • Sergei Tretiak
چکیده

We examine in detail the impact of passivating ligands (i.e., amines, phosphines, phosphine oxides and pyridines) on the electronic and optical spectra of Cd(33)Se(33) quantum dots (QDs) using density functional theory (DFT) and time-dependent DFT (TDDFT) quantum-chemical methodologies. Most ligand orbitals are found deep inside in the valence and conduction bands of the QD, with pyridine being an exception by introducing new states close to the conduction band edge. Importantly, all ligands contribute states which are highly delocalized over both the QD surface and ligands, forming hybridized orbitals rather than ligand-localized trap states. In contrast, the states close to the band gap are delocalized over the QD atoms only and define the lower energy absorption spectra. The random detachment of one of ligands from the QD surface results in the appearance of a highly localized unoccupied state inside the energy gap of the QD. Such changes in the electronic structure are correlated with the respective QD-ligand binding energy and steric ligand-ligand interactions. Polar solvent significantly reduces both effects leading to delocalization and stabilization of the surface states. Thus, trap and surface states are substantially eliminated by the solvent. Polar solvent also blue-shifts (e.g., 0.3-0.4 eV in acetonitrile) the calculated absorption spectra. This shift increases with an increase of the dielectric constant of the solvent. We also found that the approximate single-particle Kohn-Sham (KS) approach is adequate for calculating the absorption spectra of the ligated QDs. Besides a systematic blue-shift, the KS spectra are in very good agreement with their respective counterparts calculated with the more accurate TDDFT method.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Effect of PbS Film Thickness on the Performance of Colloidal Quantum Dot Solar Cells

Colloidal quantum dots offer broad tuning of semiconductor band structure via the quantum size effect. In this paper, we present a detailed investigation on the influence of the thickness of colloidal lead sulfide (PbS) nanocrystals (active layer) to the photovoltaic performance of colloidal quantum dot solar cells. The PbS nanocrystals (QDs) were synthesized in a non-coordinating solvent, 1-oc...

متن کامل

Electronic grade and flexible semiconductor film employing oriented attachment of colloidal ligand-free PbS and PbSe nanocrystals at room temperature.

Electronic grade semiconductor films have been obtained via the sintering of solution processed PbS and PbSe nanocrystals at room temperature. Prior attempts to achieve similar films required the sintering of nanocrystals at higher temperatures (>350 °C), which inhibits the processing of such films on a flexible polymer substrate, and it is also expensive. We reduced the sintering temperature b...

متن کامل

Influences of Co2+ & Er3+ Co-doping on the Structural and Physical Properties of ZnO Nanocrystals Synthesized by Hydrothermal Route

Co2+ & Er3+ co-doped ZnO nanocrystals were synthesized by the hydrothermal method at 180°C and pH= 12 for 48 h. Powder XRD patterns indicate that the Zn1-2xErxCoxO crystals (0.00<x≤0.035) are isostructural with ZnO. The cell parameters increase for Er3+ and Co2+ upon increasing the dopant content (x). SEM images show that doping of Er3+ and Co2+ into the sites of Zn2+ does not change the morpho...

متن کامل

Lead Halide Perovskites and Other Metal Halide Complexes As Inorganic Capping Ligands for Colloidal Nanocrystals

Lead halide perovskites (CH3NH3PbX3, where X = I, Br) and other metal halide complexes (MX(n), where M = Pb, Cd, In, Zn, Fe, Bi, Sb) have been studied as inorganic capping ligands for colloidal nanocrystals. We present the methodology for the surface functionalization via ligand-exchange reactions and the effect on the optical properties of IV-VI, II-VI, and III-V semiconductor nanocrystals. In...

متن کامل

Influences of Co2+ & Er3+ Co-doping on the Structural and Physical Properties of ZnO Nanocrystals Synthesized by Hydrothermal Route

Co2+ & Er3+ co-doped ZnO nanocrystals were synthesized by the hydrothermal method at 180°C and pH= 12 for 48 h. Powder XRD patterns indicate that the Zn1-2xErxCoxO crystals (0.00<x≤0.035) are isostructural with ZnO. The cell parameters increase for Er3+ and Co2+ upon increasing the dopant content (x). SEM images show that doping of Er3+ and Co2+ into the sites of Zn2+ does not change the morpho...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Nanoscale

دوره 4 3  شماره 

صفحات  -

تاریخ انتشار 2012