No abstract

Lead sulfide colloidal quantum dot solar cells (CQDSCs), the next generation of photovoltaics, are hampered by non‐radiative recombination induced by defects and an electron‐hole extraction imbalance. CQDSCs have three interfaces: CQD/CQD, electron transport layer (ETL)/CQD, and CQD/hole transport layer (HTL), and modifying one of these interfaces does not fix the problem stated above. Here, coordinated control and passivation of the three interfaces in PbS CQDSCs are presented and it is shown that the synergistic effects may improve charge transport and charge carrier extraction balance and minimize non‐radiative recombination simultaneously. A facile method is developed for epitaxially growing an ultrathin perovskite shell on the CQD surface to passivate the CQD/CQD interface, resulting in CQD absorber layers with long carrier diffusion lengths. With the introduction of organic films with adjustable electrical characteristics, the influence of ETL/CQD interfacial modifications on carrier transport and recombination is investigated. An excessive increase in the electron extraction rate reduces the fill factor and solar efficiency, as discovered. Therefore a modified layer is created at the CQD/HTL interface to promote hole extraction, which enhances charge extraction balance and passivates the interface. Finally, PbS CQDSCs exhibit a power conversion efficiency of 15.45%, a record for Pb chalcogenide CQDSCs.

Organolead trihalide perovskites (OTPs) such as CH3NH3PbI3 (MAPbI3) have attracted much attention as the absorbing layer in solar cells and photodetectors (PDs). Flexible OTP devices have also been developed. Transparent electrodes (TEs) with higher conductivity, stability, and flexibility are necessary to improve the performance and flexibility of flexible OTP devices. In this work, patterned Au nanowire (AuNW) networks with high conductivity and stability are prepared and used as TEs in self-powered flexible MAPbI3 PDs. These flexible PDs show peak external quantum efficiency and responsivity of 60% and 321 mA/W, which are comparable to those of MAPbI3 PDs based on ITO TEs. The linear dynamic range and response time of the AuNW-based flexible PDs reach ∼84 dB and ∼4 μs, respectively. Moreover, they show higher flexibility than ITO-based devices, around 90%, and 60% of the initial photocurrent can be retained for the AuNW-based flexible PDs when bent to radii of 2.5 and 1.5 mm. This work suggests a high-performance, highly flexible, and stable TE for OTP flexible devices.

Insensitive High Explosives (IHEs) have attracted considerable interest in the past three decades due to their potential application in various propellants and military warheads. 1À4 Exploration of the explosive of low impact sensitivity and high explosive performance is the fundamental problem in the energetic materials, which has not been solved yet. HMX, a sensitive explosive, is a typical highly energetic material that has been widely used in national defense industries since the 1940s. The explosion performance of HMX is high; however, it is sensitive to heat and shock. Meanwhile, TATB belongs to a class of IHEs that are insensitive or difficult to detonate. The unique high thermal stability and its resistance to physical shock are desirable properties of TATB in many applications. 5 Two methods are mainly developed to reduce the sensitivity of HMX, 6,7 one is the control of the crystal shape and quality of I-RDX (insensitive 1,3,5-trinitro-1,3,5 -triaza-cycrohexane) 8 and I-HMX, 6 and the other preparation of HMX-based plastic bonded explosive (PBX). I-RDX and I-HMX changed from a macroscopic shape and crystal quality of the crystals, but cocrystal explosive (CCE) will further improve at the molecular level. Under same circumstance, the explosion performance of PBX is reduced, whereas that of CCE remains unchanged.Novel approaches to reduce the sensitivity of HMX are now considered widely. Cocrystal technology 9À14 are so important for improving the solubility, bioavailability physical and chemical stability properties of drugs without changing their chemical structure that it is widely used for the pharmaceutical chemicals. 15À18 The cocrystal is generally accepted to be neutral complexes composed of two components bonded by hydrogen bonding, π-stacking, and Van der Waal's forces. 19,20 Hydrogen bond is essential for the structural stability of many important cocrystals. 21À24 Reports of CCE are currently very limited. Michael patented cocrystals of HMX and AP (ammonium perchlorate). 25 Zhou et al. studied on the cocrystallized explosive of urea nitrate and RDX. 26 While all of those works provide a preliminary exploration of CCE, there is still lack of the convincing characterization to confirm whether the cocrystal was formed. Our co-worker Wei et al. recently reported the theoretical designing calculation of cocrystal HMX/TATB (molar ratio 1:1) by molecular dynamics (MD) simulation. 27 The calculation indicates that the mechanical properties and stability of the explosive can be effectively improved.In this paper, we prepare a novel HMX/TATB (mass ratio 9:1 and its molar ratio is about 8:1) CCE with a so-called solvent/ nonsolvent (S/NS) process. The results demonstrate that the crystal quality and sensitivity of the prepared CCE are considerably improved compared with the HMX.