a) E gap was determined from the intersection of the EQE edge and the local EQE maximum; b) V oc was calculated from the measured J-V curves; c) V oc rad was calculated from FTPS and EL measurements; d) EQE EL is the EL quantum efficiency of the fabricated devices; e) Exp. ΔE 3 is calculated with the Equation (ΔE 3 = −kTln(EQE EL )).

No abstract

Cesium lead halide (CsPbX3) nanocrystals have great potential for photovoltaic and optoelectronic applications, but they are sensitive to oxygen, moisture, and light irradiation. Embedding these CsPbX3 nanocrystals into all‐inorganic amorphous solid matrices such as glass is expected to improve their stability. In this work, CsPbX3 nanocrystals are precipitated in boro‐germanate glasses with tunable composition, absorption, and photoluminescence. Quantum efficiency of CsPbBr3 nanocrystals in glass can be as high as ≈80% and ≈20% for CsPb(Cl/Br)3 and CsPb(Br/I)3 nanocrystals, respectively. Thermo‐ and photostabilities of CsPbX3 nanocrystals in glass are greatly improved due to the inert nature of glasses, and intense laser irradiation‐induced damage to CsPbX3 nanocrystals is recoverable through thermal annealing. With CsPbBr3 nanocrystal‐embedded glass slices, a green light‐emitting device with a luminous efficiency of ≈120 lm W−1 and an external quantum yield of ≈30% is achieved. A white‐light‐emitting device consisting of CsPbBr3 nanocrystals and CsPb(Br/I)3 nanocrystal–embedded glass slices shows luminous efficiency in the range of 50–60 lm W−1 and external quantum yield of 20–25%. The thermo‐ and photostabilities along with the chemical stability of CsPbX3 nanocrystal–embedded glasses are promising materials for photoluminescence related applications.

The photoluminescence properties of perovskite CsPbBr QDs embedded in glasses were investigated at cryogenic temperature in the range of 40-240 K. CsPbBr QDs with radii of 3.3 nm, 4.2 nm and 4.8 nm were precipitated in phosphate glasses using conventional thermal treatment. Photoluminescence (PL) integral intensities, bandgap energies and full with at half maximum of the PL bands of CsPbBr QDs showed a strong dependence on temperature. An exciton binding energy of ∼40 meV was derived from the temperature-dependent emission intensity. Optical phonon energy involved in the exciton-phonon interaction was found to be ∼56 meV, about three times as that of the single phonon energy. Exciton-phonon coupling strength and the lattice thermal expansion coefficient were strongly dependent on the size of CsPbBr QDs, and as a result, inflection temperature of the PL peak energies of CsPbBr QDs increased as the size increased.

CdSe quantum dots (QDs) doped glasses have been widely investigated for optical filters, LED color converter and other optical emitters. Unlike CdSe QDs in solution, it is difficult to passivate the surface defects of CdSe QDs in glass matrix, which strongly suppress its intrinsic emission. In this study, surface passivation of CdSe quantum dots (QDs) by Cd1−xZnxSe shell in silicate glass was reported. An increase in the Se/Cd ratio can lead to the partial passivation of the surface states and appearance of the intrinsic emission of CdSe QDs. Optimizing the heat-treatment condition promotes the incorporation of Zn into CdSe QDs and results in the quenching of the defect emission. Formation of CdSe/Cd1−xZnxSe core/graded shell QDs is evidenced by the experimental results of TEM and Raman spectroscopy. Realization of the surface passivation and intrinsic emission of II-VI QDs may facilitate the wide applications of QDs doped all inorganic amorphous materials.

No abstract

A phase-changing polymer comprising stearyl acrylate and a long-chain urethane diacrylate was studied as a new bistable electroactive polymer. The abrupt and reversible phase transition of the crystalline aggregates of the stearyl moieties results in a rapid shift between the rigid and rubbery states of the polymers during temperature cycles. The transition temperature is tunable between 34−46 °C. A storage modulus change of ∼1000 fold can be obtained within a narrow temperature range of 10 °C. The polymer shows excellent shape memory properties with both fixation rate and recovery rate close to 100%. Diaphragm actuators based on the polymer thin films were electrically actuated up to 70% strain at 50 °C. The actuated shape can be "frozen" after the films were allowed to cool below the transition temperature. This rigid-to-rigid deformation is refreshable and repeatable via the rigid-to-rubbery transition and electrical actuation in the rubbery state.

This paper reports the effect of Er2O3 concentration on nucleation and optical properties of PbS quantum dots (QDs) formed in a silicate glass under heat treatment at 490° or 500°C. As Er2O3 concentration increased from 0.1 to 0.4 mol%, average radii of PbS QDs decreased from ∼5 to ∼4 nm, and peak wavelengths of absorption and photoluminescence also decreased. Clusters of Er3+ ions connected by bridging oxygens may act as the nucleation centers for PbS QDs.