ABSTRACT
Perovskite film generally has rough surface morphology due to the voids between the grain domains. Smoothed interface contact between the perovskite layer and the top electrode is critical for planar perovskite solar cells. We reported high efficiency bromine-iodine based perovskite solar cells with a flattening cathode interface by incorporating a solution-processed bathocuproine (sBCP) interfacial layer at the cathode side. Compared with vacuum evaporated bathocuproine (eBCP), sBCP demonstrated an excellent surface modification effect at the cathode side with very smaller charge transfer resistance. Accordingly, a high fill factor exceeding 85% and a power conversion efficiency exceeding 13% in CH3NH3PbI3-xBrx based perovskite solar cells were achieved. The largely improved fill factor was attributed to the smooth film morphology and full surface coverage of perovskite films modified by the solution-processed BCP layer.
ABSTRACT
In this work, NH2CH=NH2PbI3 (FAPbI3) was employed for light harvesting in inverted planer perovskite solar cells for the first time. Except for the silver cathode, all layers were solution-processed under or below 140 °C. The effect of the annealing process on device performance was investigated. The FAPbI3 solar cells based on a slowed-down annealing shows superior performance compared to the CH3NH3PbI3 (MAPbI3)-based devices, especially for the short circuit current density. A power conversion efficiency of 13.56% was obtained with high short circuit current density of 21.48 mA cm(-2). This work paves the way for low-temperature fabrication of efficient inverted planer structure FAPbI3 perovskite solar cells.
ABSTRACT
Lithium hydride (LiH) is employed as a novel n-dopant in the intermediate connector for tandem organic light-emitting diodes (OLEDs) because of its easy coevaporation with other electron transporting materials. The tandem OLEDs with two and three electroluminescent (EL) units connected by a combination of LiH doped 8-hydroxyquinoline aluminum (Alq3) and 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) demonstrate approximately 2-fold and 3-fold enhancement in current efficiency, respectively. In addition, no extra voltage drop across the intermediate connector is observed. Particularly, the lifetime (T75%) in the tandem OLED with two and three EL units is substantially improved by 3.8 times and 7.4 times, respectively. The doping effect of LiH into Alq3, the charge injection, and transport characteristics of LiH-doped Alq3 are further investigated by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS).
ABSTRACT
A simple and cheap method for depositing solution-processed GeO2 (sGeO2) film is proposed utilizing the weak solubility of GeO2 in water. X-ray photoelectron spectroscopy analysis reveals that a pure GeO2 thin film can be formed by casting its aqueous solution. This method can avoid the difficulty of vacuum evaporation by its high melting point. The sGeO2 film has been used successfully as an anode interfacial layer in poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (IC60BA)-based bulk heterojunction organic solar cells with improved power conversion efficiency and device stability compared with that using conventional poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS); the improvement of the power conversion efficiency and the device stability are estimated to be 9% and 50%, respectively. The calculations of optical intensity in a whole cell demonstrate that a thin layer of sGeO2 could function as an optical spacer in the based bulk heterojunction (BHJ) organic solar cells (OSCs) for enhancing the light harvesting in the active layer. Interfacial evaluation by impedance spectroscopy shows that the sGeO2-based cell exists less charge carrier recombination and lower contact resistance. More importantly, the sGeO2 film processing is very simple and environmentally friendly, which has potential applications in green and low-cost organic electronics in the future.
ABSTRACT
A novel silicon-based compound, 10-phenyl-2'-(triphenylsilyl)-10H-spiro[acridine-9,9'-fluorene] (SSTF), with spiro structure has been designed, synthesized, and characterized. Its thermal, electronic absorption, and photoluminescence properties were studied. Its energy levels make it suitable as a host material or exciton-blocking material in blue phosphorescent organic light-emitting diodes (PhOLEDs). Accordingly, blue-emitting devices with iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C(2)']picolinate (FIrpic) as phosphorescent dopant have been fabricated and show high efficiency with low roll-off. In particular, 44.0â cd A(-1) (41.3â lm W(-1)) at 100â cd m(-2) and 41.9â cd A(-1) (32.9â lm W(-1)) at 1000â cd m(-2) were achieved when SSTF was used as host material; 28.1â lm W(-1) at 100â cd m(-2) and 20.6â lm W(-1) at 1000â cd m(-2) were achieved when SSTF was used as exciton-blocking layer. All of the results are superior to those of the reference devices and show the potential applicability and versatility of SSTF in blue PhOLEDs.
ABSTRACT
This paper investigates the effects of localized surface plasmon resonance (LSPR) in an inverted polymer/fullerene solar cell by incorporating Au and/or Ag nanoparticles (NPs) into the TiO2 buffer layer. Enhanced light harvesting via plasmonic resonance of metal NPs has been observed. It results in improved short-circuit current density (Jsc) while the corresponding open-circuit voltage (Voc) is maintained. A maximum power conversion efficiency of 7.52% is obtained in the case of introducing 30% Ag NPs into the TiO2, corresponding to a 20.7% enhancement compared with the reference device without the metal NPs. The device photovoltaic characteristics, photocurrent properties, steady-state and dynamic photoluminescences of active layer on metal NP-doped TiO2, and electric field profile in metal NP-doped TiO2 layers are systematically investigated to explore how the plasmonic effects of Au and/or Ag NPs influence the OSC performance.
