Supporting Information for: Enhancing the Performance of CdSe/CdS Dot-in- Rod Light Emitting Diodes via Surface Ligand.

Transcription

1 Supporting Information for: Enhancing the Performance of CdSe/CdS Dot-in- Rod Light Emitting Diodes via Surface Ligand Modification Prachi Rastogi a,b, Francisco Palazon a, Mirko Prato c, Francesco Di Stasio a,* and Roman Krahne a,* a Nanochemistry Department, Istituto Italiano di Tecnologia, Via Morego 30, Genova, Italy b Dipartimento di Chimica e Chimica Industriale, Università degli Studi di Genova, Via Dodecaneso 31, Genova, Italy c Materials Characterization Facility, Istituto Italiano di Tecnologia, Via Morego 30, Genova, Italy * corresponding author roman.krahne@iit.it, francesco.distasio@iit.it S-1

2 Structure of the molecules. Figure S1. Structure of the different ligands used for the surface passivation of the DiRs. Optical properties of DiRs in solution. Figure S2. Optical properties of the DiR solutions (see Materials and Methods section for the ligand exchange procedure in solution). (a) Absorption and photoluminescence, (b) PL decay recorded at 632 nm. The table summarizes the optical properties measured from the DiRs in solution. S-2

3 Fitting of PL decay. The decay traces of the PL were fitted by a classic two-exponential function: F t = A % exp t τ % + A, exp t τ, (1) and τ -. is then: τ -. = - / 0 / / 0 / (2) With the quantum yield (QY) and average lifetime values, we can calculate the average radiative and non-radiative decay rates, using the two equations: in which rad respectively. 1,2 QY = τ -. = :9;678 (3) % :9;678 (4) G and G non-rad are the average radiative and non-radiative decay rates, Table S1. Optical properties of CdSe/CdS DiRs in solution and in films. In solutions In films Ligands Peak FWH Effective PLQY Peak FWHM Effective PLQY wavelength M lifetimeτ eff (%) wavelength (nm) lifetime τ eff (%) λ p (nm) (nm) (ns) λ p (nm) (ns) ODPA SCN MPA AET S-3

4 Layer-by-layer deposition procedure. Figure S3. Upper part: Schematic illustration of the LbL deposition process. Lower part: Scanning electron microscopicy images of pristine ODPA (a) and ligand exchanged AET (b), MPA (c), and SCN (d) DiR in films. S-4

5 Figure S4. Atomic force microscopy images of (a) an ODPA-coated nanocrystal film fabricated in a single spin-coating step, and (b) an AET-coated nanocrystal film fabricated by eight layer-by-layer depositions. The images were recorded in non-contact mode with a Nanosurf Easy-scan system. Figure S5. Fourier Transform infrared spectra recorded from ODPA-capped and ligand exchanged DiR films. The spectra are shifted vertically for clarity. The measurements were performed with a Vertex 70V spectrometer from Bruker Optics. S-5

6 Light-emitting diodes. Figure S6. (a) Scanning electron microscopy cross section image of a typical LED. (b) Band scheme of the LED architecture, showing also the influence of the core-shell DiR structure. Figure S7. Histograms of the EQE achieved from ODPA (a) and AET (b) based LEDs. S-6

7 Figure S8. Luminance and EQE of the ODPA and AET functionalized DiR LEDs recorded at several intervals after device fabrication. (a) and (b) show the J-V-L characteristics of an ODPA DiR LED, (c) and (d) represent the J-V-L characteristics of an AET capped LED. The color coding and legend depict the number of days after device fabrication. References. 1. Lakowicz, J. R. Principles of fluorescence spectroscopy; Springer US, Omogo, B.; Aldana, J. F.; Heyes, C. D. J. Phys. Chem. C 2013, 117 (5), S-7