Naibo Chen

Quasi-two-dimensional (quasi-2D) perovskite has the advantage of enlarging exciton binding energy and is more suitable for efficient perovskite light-emitting diodes (PeLEDs). However, the quasi-2D perovskite films deposited with solution methods are usually mixtures of multiple phases with different inorganic layer numbers (n), unfavorable to obtaining high emission efficiency. In this study, we selected formamidinium lead bromide (FAPbBr3) as the light emitter and (2-phenylethyl)ammonium cation (PEA+) as the long-chain organic spacer cation to prepare high-n (n = 9) quasi-2D perovskite films with improved phase purity. Based on the multiple cations mixed engineering, the quality of these films improved obviously by partly replacing FA+ with minute quantities of cesium cation (Cs+). The improvement focused on remarkably enhanced photoluminescence, few low-n phases, and decreased grain sizes. The green PeLED based on the performance-optimized and phase purity-improved high-n quasi-2D perovskite reached a high brightness of 28 960 cd/m2 together with a maximum current efficiency of 44.8 cd/A and a maximum external quantum efficiency of 9.99%.

Aqueous CdTe quantum dots solar cells have been successfully fabricated by the blade coating method on the magnesium zinc oxide (Zn_1−xMg_xO or ZMO) window layer. Compared with the ZMO mono-window layer, the ZMO/CdS bi-window layer can decrease the interface recombination effectively due to the lower lattice mismatch and fast interdiffusion between CdS and CdTe. Moreover, the high temperature annealing of the CdTe quantum dots absorbed layer passivates the grain boundary of the CdTe crystalline via the replacement reaction of tellurium with sulfur. Finally, the conversion efficiency of our aqueous CdTe quantum dots solar device is improved from 3.21% to 8.06% with the introduction of the CdS interlayer and high temperature CdCl₂ annealing. Our aqueous CdTe quantum dots solar devices show a large open circuit voltage and fill factor which are comparable with the conventional devices that are fabricated with organic CdTe quantum dots. We believe that it is the spike-like conduction band alignment between the ZMO and CdTe absorbed layer that reduces the majority carrier concentration, leading to the decrease in interface recombination probability.

Small organic molecules (SOMs) with fascinating chiroptical properties have received much attention for their potential applications in photoelectric and biological devices. As an important research tool, circularly polarized luminescence (CPL) provides information about the chiral structures of these molecules in their excited state, and has been an active area of research. With the development of the commercially available CPL instrumentation, currently, more and more research groups have attempted to enhance the CPL parameters (i.e., quantum yield and dissymmetry factor) of the chiral SOMs from all aspects. This review summarizes the latest five years progresses in research on the experimental techniques and theoretical calculations of CPL emitted from SOMs, as well as forecasting its trend of development.