Synthesis of Type II CdTe−CdSe Nanocrystal Heterostructured Multiple-Branched Rods and Their Photovoltaic Applications

Abstract

Novel type II CdTe−CdSe semiconductor nanocrystal heterostructures (SNCHs) with multiple-branched rod morphology were synthesized by epitaxial growth of CdSe from CdTe nanocrystals in solution, and the SNCHs were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD) analysis. The SNCHs are composed of a CdTe core and CdSe branches, and most of the heterostructured nanocrystals have about 10 branched rods with thickness of 3−5 nm and length of 10−30 nm. The absorption spectra of the SNCHs covered the whole visible region from 380 to 780 nm with a distinct peak at 560∼580 nm corresponding to the absorption of CdSe nanocrystals. The quenching of the photoluminescence (PL) peak of the CdTe core was observed in the SNCHs, which indicates that photoinduced charge separation existed in the SNCHs. Furthermore, the photovoltaic properties of the SNCHs were studied on the basis of the devices with single component of the SNCHs and with the blend of P3HT and the SNCHs. The device based on the SNCHs single component showed an open-circuit voltage (V oc) of 0.40 V, a short-circuit current density (J sc) of 0.018 mA/cm2, fill factor (FF) of 38%, and power convention efficiency (η) of 0.003% under the illumination of AM1.5, 100 mW/cm2, which is greatly improved in comparison with that of the homostructured semiconductor nanocrystals. For the hybrid P3HT/SNCHs device, the J sc, V oc, FF, and η of the device reached 0.58 mA/cm2, 0.63V, 43%, and 0.16% respectively.

Synthesis and Thermoelectric Properties of Noble Metal Ternary Chalcogenide Systems of Ag–Au–Se in the Forms of Alloyed Nanoparticles and Colloidal Nanoheterostructures

“…16,24,25 Just as a tiny fraction of numerous examples, type II-semiconductor heterostructures such as CdSe@CdTe multibranched NPs, metal-semiconductor hybrid systems such as Au(Pt)-CdSe nanodumbbells or Au(Pt)-Cu 2 ZnSnS 4 NPs, bimetallic core@shell Co@Cu or FePd@Pd nanostructures and narrow band gap semiconductor core-shell PbTe@PbS NPs have shown to be efficient systems for optoelectronic, catalytic and thermoelectric applications. [26][27][28][29][30][31][32][33] Furthermore, colloidal NPs can then be used as pre-engineered building blocks for constructing a nanostructured extended solid with virtually unlimited control over its compositional and morphological features. 25,34,35 The most straightforward advantage of this method resides in the fact that a sub-nanometer compositional control is achieved already in the building blocks before the formation of the final composite, guaranteeing a high homogeneity in the latter.…”

Improved Photovoltaic Performance of Heterostructured Tetrapod‐Shaped CdSe/CdTe Nanocrystals Using C60 Interlayer

“…Figure 3a ). These performances are improved with respect to those reported so far for similar all-nanocrystal devices based on CdTe/CdSe tetrapods, [19] and also higher than those reported for single-material devices based only on CdSe or CdTe nanocrystals.…”

“…[15][16][17][18] Joining together in a single nanostructure two materials with a type-II band offset can induce spatial separation of photogenerated carriers within the nanostructure itself, with the electron residing in one material and the hole in the other. This capability to intrinsically dissociate photogenerated excitons [15][16][17][18][19] renders these nanocrystals excellent candidates for application in PV devices. [19] Our group reported recently an approach to prepare heterostructured tetrapod-shaped colloidal nanocrystals based on a CdSe core region and CdTe arms (see sketches in Fig.…”

“…This capability to intrinsically dissociate photogenerated excitons [15][16][17][18][19] renders these nanocrystals excellent candidates for application in PV devices. [19] Our group reported recently an approach to prepare heterostructured tetrapod-shaped colloidal nanocrystals based on a CdSe core region and CdTe arms (see sketches in Fig. 2a and b).…”

Type-II Core/Shell Nanowire Heterostructures and Their Photovoltaic Applications

“…In addition, type-II heterojunction can also substantially reduce bandgap indirectly in spatial to efficiently absorb the sun light, although both materials constituting heterostructure have wider bandgaps [20,23]. Such heterojunctions have been intensively investigated for photovoltaic applications, including dye-sensitized solar cell (DSSC) [24,25], quantum dot-sensitized solar cell (QDSSC) [12,26], core/shell nanowire solar cells [27,28], and so on [29][30][31][32][33][34][35]. Compared with DSSC or QDSSC, core/shell nanowire solar cells have the advantages in light absorption, current transportation and charge separation [18][19][20]36].…”