Ternary metal chalcogenides such as CuInS2 offer new opportunities to design quantum dot solar cells (QDSC). Chemically synthesized CuInS2 quantum dots (particle diameter, 2.6 nm) have been successfully deposited within the mesoscopic TiO2 film using electrophoretic deposition (150 V cm(-1) dc field). The primary photoinduced process of electron injection from excited CuInS2 into TiO2 occurs with a rate constant of 5.75 × 10(11) s(-1). The TiO2/CuInS2 films are photoactive and produce anodic photocurrent with a power conversion efficiency of 1.14%. Capping the TiO2/CuInS2 film with a CdS layer decreases the interfacial charge recombination and thus offers further improvement in the power conversion efficiency (3.91%). The synergy of using CdS as a passivation layer in the composite film is also evident from the increased external quantum efficiency of the electrode in the red region where only CuInS2 absorbs the incident light.

Growing demand for clean energy has intensified the interest in understanding the properties of environmentally friendly materials for future energy devices. Indium phosphide (InP) is relatively nontoxic as compared to cadmium chalcogenides, and herein we demonstrate the successful use of this material for resonance energy transfer applications. Three chromophoric dyes, namely, lissamine rhodamine B ethylene diamine (LiRh), Texas red cadavarine C5 (TxRed), and rhodamine 101 (Rh101), possessing free anchoring groups were used as acceptors in InP quantum dot (QD)-based donor−acceptor pairs. The energy transfer process was monitored by steady-state and time-resolved emission spectroscopic techniques. Large values of quenching constant (k q ), in the range of 10 13 −10 14 M −1 s −1 , observed on addition of chromophoric dyes to InP overcoated with zinc sulphide (InP/ZnS), confirm that the interaction is predominantly static in nature. Selective excitation of the QD component at 405 nm showed a rapid decay of InP/ZnS emission and a concomitant growth of the acceptor emission (rise time of ∼200 ps), indicating that all these systems follow a nonradiative energy transfer mechanism. Time-resolved emission studies confirm that the photoexcited InP/ZnS QDs decays to the ground state by transferring the excitation energy to the chromophoric dyes leading to the formation of its excited state. The high efficiency of energy transfer observed in these systems further confirms that InP is an excellent energy harvester with potential use in biomedical and photovoltaic applications.

Photoinduced charge-transfer dynamics between CdSe quantum dots (QDs) possessing varying monolayers of ZnS and hole scavengers such as phenothiazine (PT) and N-methylphenothiazine (NMPT) were investigated for optimizing the shell thickness of core−shell quantum dots. Spectroscopic investigations indicate that phenothiazine binds onto the surface of bare CdSe QDs, resulting in the photoluminescence quenching, and two monolayers of ZnS prevent the electron-transfer process. Methodologies presented here can provide quantitative information on the optimum shell thickness of core−shell QDs, which can suppress the undesired electron transfer and provide maximum luminescence yield.

The effect of hydrazine on the photophysical and morphological properties of water-soluble thioglycolic acid-capped cadmium telluride (CdTe) nanoparticles at room temperature has been investigated. At lower concentrations of hydrazine (0.5 M), a large enhancement in the luminescence of CdTe nanoparticles was observed without any shape change; hydrazine saturates the Cd dangling bonds on the nanoparticles’ surface through coordination. Interestingly, highly crystalline CdTe nanowires with hexagonal wurtzite structure were obtained at higher concentrations of hydrazine (2.0 M) through the recrystallization of linearly assembled aggregated CdTe nanoparticles with a zinc blend structure. Strong dipole−dipole interaction between the nanoparticles in the presence of hydrazine assists their linear aggregation, and low activation energy for phase-transition drives their recrystallization to nanowires. Extremely simple methodology presented here opens up novel pathways for the synthesis of one-dimensional semiconductor nanostructures at room temperature and provides valuable information about the growth mechanism of nanowires.

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