A Multistate Thermoresponsive Smart Window Based on a Multifunctional Luminescent Solar Concentrator.

Conventional luminescent solar concentrators (LSCs) usually only have the ability to absorb solar energy and convert it to electricity but are not able to regulate the transmitted light. Herein, a multistate thermoresponsive smart window (SW) based on LSC has been fabricated, in which the stimuli-responsive host layer consists of polydimethylsiloxane (PDMS) and ethylene glycol solution (EGS) microdroplets stacking with LSC layer-based on near-infrared (NIR) CuInSe2-xSx/ZnS core/shell quantum dots (QDs) and PDMS matrix. As-synthesized CISSe/ZnS QDs with broad NIR absorption in LSC exhibit controllable emission spectra over 833-1088 nm and high photoluminescence (PL) quantum yield from 45 to 83%. Coupling with Si solar cells as a reference, optimized LSC-SW devices with dimensions of 5 × 5 × 0.9 cm3 exhibit higher power conversion efficiency (PCE) of 1.19-1.36% with increased temperature from 0 to 50 °C than those of sole LSC and SW devices. The corresponding visible light transmissions are regulated from 75.1 to 48.1% accordingly. The improvement of PCEs in an opaque state is mainly due to enhanced absorption of QDs originating from rescattered photons from the EGS/PDMS layer, leading to more emitted photons reaching photovoltaics. This work is expected to bring up new opportunities for applications in greenhouses, building facades, and energy-efficient smart windows.

Highly efficient and stable tandem luminescent solar concentrators based on carbon dots and CuInSe2-xSx/ZnS quantum dots.

Semi-transparent large-area luminescent solar concentrators (LSCs) have been considered an essential part of zero-energy or low-energy consuming buildings in the future. Inorganic colloidal quantum dots (QDs) are promising candidates for LSCs due to the advantages of a tunable bandgap, engineered large Stokes shift, and relatively high photoluminescence (PL) quantum yield. However, LSCs that are fabricated using colloidal quantum dots exhibited an inferior stability under long-term illumination, demanding great efforts to explore the highly stable LSCs. Herein, we fabricated large-area (∼100 cm2) tandem LSCs based on highly stable carbon dots (CDs) and highly luminescent near-infrared emitting CuInSe2-xSx/ZnS (CuInSeS/ZnS) QDs. Coupled with a Si diode as a reference, the power conversion efficiency of the corresponding tandem (dimensions: 10 × 10 × 0.5 cm3) and single LSCs (dimensions: 10 × 10 × 0.3 cm3) based on CuInSeS/ZnS QDs under one sun illumination are 0.46% and 0.5%, respectively. For single CuInSeS/ZnS QD based LSCs at a low concentration (0.039 wt%), external and internal quantum efficiencies reach up to 2.87% and 36.37%, respectively. After UV illumination for 8 h, bottom LSCs based on CuInSeS/ZnS QDs retain 93.22% of the initial PL emission, which is higher than that of LSCs (∼80%) without the CD protection. The highly efficient and stable tandem LSCs employing green CDs and NIR CuInSeS/ZnS QDs as PL emitters pave the way for the realization of large area building-integrated photovoltaic (BIPV) devices.

Fast and Reversible Quasi-Solid-State Anion Exchange in Highly Luminescent CsPbX3 Perovskite Nanocrystals for Dual-Mode Encryption-Decryption.

Solid-state anion exchange method is easy to handle and beneficial to improve stability of CsPbX3 (X = Cl, Br, I) perovskites nanocrystals (NCs) with respect to anion exchange in liquid phase. However, the corresponding exchange rate is rather slow due to the limited diffusion rate of anions from solid phases, resulting in mixed-halide perovskite NCs. Herein,  a fast and reversible post-synthetic quasi-solid-state anion exchange method in CsPbX3 NCs with inorganic potassium halide KX salts/polyvinylpyrrolidone (PVP) thin film is firstly reported. Original morphology of the exchanged NCs is well-preserved for all samples. Complete anion exchange from Br- to Cl- or I- is successfully achieved in CsPbX3 NCs within ≈20 min through possible vacancies-assisted ion exchange mechanism, under ambient conditions and vice versa. Particularly, Br- -exchanged CsPbCl3 and CsPbI3 NCs exhibit improved optical properties. Encouraged by the attractive fluorescence and persistent luminescence as well as good stability of the resulted CsPbX3 NCs, an effective dual-mode information storage-reading application is demonstrated.  It is believed that this method can open a new avenue for the synthesis of other direct-synthesis challenging quantum-confined perovskite NCs/nanoplates/nanodisks or CsSnX3 NCs/thin film and provide an opportunity for advanced information storage compatible for practical applications.