The strategies for preparing blue perovskite light-emitting diodes

Metal halide perovskites have attracted tremendous interest due to their excellent optical and electrical properties,and they find many promising applications in the optoelectronic fields of solar cells,light-emitting diodes,and photodetectors.Thanks to the contributions of international researchers,significant progress has been made for perovskite light-emitting diodes(Pero-LEDs).The external quantum efficiencies(EQEs)of Pero-LEDs with emission of green,red,and near-infrared have all exceeded 20%.However,the blue Pero-LEDs still lag due to the poor film quality and deficient device structure.Herein,we summarize the strategies for preparing blue-emitting perovskites and categorize them into two:compositional engineering and size controlling of the emitting units.The advantages and disadvantages of both strategies are discussed,and a perspective of preparing high-performance blue-emitting perovskite is proposed.The challenges and future directions of blue PeroLEDs fabrication are also discussed.

电泳法制备的致密氧化锡薄膜及其在高稳定性钙钛矿太阳能电池中的应用

在平面型钙钛矿太阳能电池中常采用SnO_(2)作为电子传输层材料,相应的SnO_(2)薄膜常采用溶液旋涂法制备。但是由于前驱液中的纳米颗粒可能会发生部分团聚、基底和溶液难以完全避免灰尘等杂质颗粒混入,且最佳的SnO_(2)电子传输层的厚度通常仅有约20 nm,所以这种方法制备的电子传输层难以保证严格致密和无纳米针孔。在本工作中,我们报道了一种电泳沉积制备致密SnO_(2)薄膜的方法,并用其有效地提高了钙钛矿太阳能电池的光电转换效率和工况稳定性。通过电泳法,表面带负电荷的SnO_(2)纳米颗粒在电场的作用下沉积到氧化铟锡(ITO)阳极表面,这种方法得到的薄膜比旋涂法制备的更为致密。将其应用于n-i-p结构的钙钛矿太阳能电池中,能够使得暗电流降低并抑制载流子的非辐射复合,从而提高电池的短路电流和开路电压,进而实现更高的光电转换效率(从18.17%提高到19.52%),且能消除迟滞效应。更重要的是,长期工况稳定性测试表明基于电泳-旋涂法制备的器件在1个太阳的光照下、最大功率点处连续工作960 h后,仍然能够保持71%的初始效率;然而基于旋涂法制备的器件在工作100 h后即降低到初始效率的70%。本工作提供了一种全新的SnO_(2)电子传输层的制备方法,显著地提高了器件性能和工况稳定性,后续有望应用于制备大面积器件和电池模组。

The Extremely Low Frequency Engineering Project for Underground Exploration

1.Introduction Super-low-frequency(SLF)(30-300 Hz)electromagnetic technology was first used in military to submarine deep water communications.In the 1950s,to strengthen the concealment and survivability of strategic missile nuclear submarines,both the United States and the Soviet Union began to study SLF communications,with the aim of achieving communications between land command centers and submarines at depths of below 100 m and distances of thousands of kilometers.

Boosting CsSnI3-based near-infrared perovskite lightemitting diodes performance via solvent coordination engineering

Due to their unique photoelectric properties,nontoxic tin-based perovskites are emerging candidates for efficient near-infrared LEDs.However,the facile oxidation of Sn2+and the rapid crystallization rate of tin-based perovskites result in suboptimal film quality,leading to inferior efficiencies of tin-based perovskite light-emitting diodes(Pero-LEDs).In this study,we investigate the influence of commonly used solvents on the quality of the CsSnI3 films.Remarkably,DMSO exhibits a stronger interaction with SnI2,forming a stable intermediate phase of SnI2·3DMSO.This intermediate effectively inhibits the oxidation of Sn2+and slows down the crystallization rate,bringing in lower defect state density and higher photoluminescence quantum yield of the pre-pared perovskite films.Consequently,the corresponding Pero-LEDs achieve a maximum external quantum efficiency(EQE)of 5.6%,among the most effi-cient near-infrared Pero-LEDs.In addition,the device processes ultra-low effi-ciency roll-off and high reproducibility.Our research underscores the crucial role of solvent-perovskite coordination in determining film quality.These find-ings offer valuable guidance for screening solvents to prepare highly efficient and stable tin-based perovskites.

Composition engineering to obtain efficient hybrid perovskite light-emitting diodes

Metal halide perovskites have received considerable attention in the field of electroluminescence,and the external quantum efficiency of perovsk'c lightemitting diodes has exceeded 20%.CH3NH3PbBr3 has been intensely investigated as an emitting layer in perovskite light-emitting diodes.However,perovskite films comprising CH3NH3PbBr3 often exhibit low surface coverage and poor crystallinity,leading to high current leakage,severe nonradiative recombination,and limited device performance.Herein,we demonstrate a rationale for composition engineering to obtain high-quality perovskite films.We first reduce pinholes by adding excess CH3NH3B1 to the actual CH3NH3PbBr3 films,and we then add CsBr to improve the crystalline quality and to passivate nonradiative defects.As a result,the(CH3NH3)1-xCSxPbBx based perovskite light-emitting diodes exhibit significantly improved external quantum and power efficiencies of 6.97%and 25.181m/W,respectively,representing an improvement in performance dozens of times greater than that of pristine CH3NH3PbBr3-based perovskite light-emitting diodes.Our study demonstrates that composition engineering is an effective strategy for enhancing the device performance of perovskite light-emitting diodes.

Efficient and stable inverted perovskite solar cells enabled by inhibition of self-aggregation of fullerene electron-transporting compounds

Fullerene-based electron-transporting layers(ETLs)significantly influence the defect passivation and device performance of inverted perovskite solar cells(PSCs).However,theπ-cage structures of fullerenes lead to a strong tendency to self-aggregate,which affects the long-term stability of the corresponding PSCs.Experimental results revealed that[6,6]-phenyl-C61-butyric acid methyl ester(PCBM)-based ETLs exhibit a certain degree of self-aggregation that affects the stability of the device,particularly under continuous irradiation stress.To modulate the aggregation behavior,we replaced a methyl hydrogen of PCBM with a phenyl group to yield[6,6]-phenyl-C61-butyric acid benzyl ester(PCBB).As verified through X-ray crystallography,this minor structural modification results in more non-covalent intermolecular interactions,which effectively enhanced the electron-transporting ability of the PCBB-based ETL and led to an efficiency approaching 20%.Notably,the enhanced intermolecular forces of PCBB suppressed its self-aggregation,and the corresponding device showed significantly improved stability,retaining approximately 90%of its initial efficiency after 600 h under one-sun irradiation with maximum power point tracking.These findings provide a viable approach for the design of new fullerene derivatives to tune their intermolecular interactions to suppress self-aggregation within the ETL for highperformance PSCs.