Carbon-based nanomaterials hold promise for eco-friendly alternatives to heavy-metal-containing quantum dots (QDs) in optoelectronic applications. Here, boric acid-functionalized graphene quantum dots (B-GQDs) were prepared using bottom-up molecular fusion based on nitrated pyrenes and boric acid. Such B-GQDs with crystalline graphitic structures and hydrogenbonding functionalities would be suitable model systems for unraveling the photoluminescence (PL) mechanism, while serving as versatile building blocks for supramolecular self-assembly. Unlike conventional GQDs with multiple emissive states, the B-GQDs exhibited excitation-wavelength-independent, vibroniccoupled excitonic emission. Interestingly, their PL spectra can be tuned without largely sacrificing the quantum yield (QY) due to two-dimensional self-assembly. In addition, such B-GQDs in a polystyrene matrix possessed an ultrahigh QY (∼90%) and large exciton binding energy (∼300 meV). Benefiting from broadband absorption, ultrahigh QY, and long-wavelength emission, efficient laminated luminescent solar concentrators (100 × 100 × 6.3 mm 3 ) were fabricated, yielding a high power conversion efficiency (1.4%).
Fullerene derivative thin films have been widely used in inverted-type perovskite solar cells as the electron transport layer (ETL) and hole blocking layer. However, the smooth contact at the interface between the hydrophobic [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and hydrophilic CH3NH3PbI3 (MAPbI3) thin film has not yet been completely understood. The contact at the PCBM/MAPbI3 interface strongly influences the photovoltaic performance. The photovoltaic devices were characterized by measuring the light intensity-dependent current density–voltage (J–V) curves and impedance spectra, which show that the contact at the PCBM/MAPbI3 interface simultaneously influences the shunt resistance (carrier recombination) and series resistance (interfacial contact). In addition, x-ray diffraction patterns, atomic force microscopic images, absorbance spectra and photoluminescence spectra were used to explore the contact at the PCBM/MAPbI3 interface. The experimental results show that the flat MAPbI3 thin film cannot be completely covered by a PCBM thin film and thereby results in the s-shape characteristic in the J–V curve of the resultant solar cells. The s-shaped J–V curve can be suppressed by increasing the crystallinity and surface roughness of the MAPbI3 thin film. With the use of an interface modification layer in between the PCBM thin film and Ag cathode, the power conversion efficiency of MAPbI3 solar cells can be increased from 10.50% to 13.71%.
he quasi Fermi level for electrons in the soft perovskite crystalline thin film and the contact qualities at the PCBM/perovksite and perovskite/P3CT-Na interfaces can be increased by using a facile...
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