Low band-gap, soluble conjugated copolymers were synthesized from 9,9-dioctylfluorene and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (PFO-DBT) and different composition ratios were used for the donor material in bulk heterojunction polymer photovoltaic cells (PVCs). In PVCs made with PFO-DBT:PCBM (methano-fullerene [6,6]-phenyl C61-butyric acid methyl ester) blends, the spectral response is extended up to 650 nm and the open-circuit voltage (Voc) is improved to 0.95 V. The energy conversion efficiency (ηe) in devices with optimized composition reaches 2.24% under an AM1.5 solar simulator (78.2 mW/cm2). In contrast to organic PVCs previously published, these PVCs retain high energy conversion efficiency at illumination up to 5 suns of AM1.5 spectral illumination. This feature allows high efficiency polymer PVC modules made in combination with a light concentrator.
A novel convenient and efficient approach to produce CsSnI3 QDs through a one-pot synthesis is employed to largely enhance the PCE of lead-free perovskite solar cells (PVSCs). The CsSnI3 QD-based device has the maximum PCE of 5.03%, which is the highest performance for all-inorganic lead-free PVSCs reported so far.
Improvement of energy density is an urgent task for developing advanced supercapacitors. In this paper, aqueous supercapacitors with high voltage of 1.8 V and energy density of 29.1 W h kg(-1) were fabricated based on carbon nanofibers (CNFs) and Na2SO4 electrolyte. The CNFs with radially grown graphene sheets (GSs) and small average diameter down to 11 nm were prepared by electrospinning and carbonization in NH3. The radially grown GSs contain between 1 and a few atomic layers with their edges exposed on the surface. The CNFs are doped with nitrogen and oxygen with different concentrations depending on the carbonizing temperature. The supercapacitors exhibit excellent cycling performance with the capacity retention over 93.7% after 5000 charging-discharging cycles. The unique structure, possessing radially grown GSs, small diameter, and heteroatom doping of the CNFs, and application of neutral electrolyte account for the high voltage and energy density of the present supercapacitors. The present supercapacitors are of high promise for practical application due to the high energy density and the advantages of neutral electrolyte including low cost, safety, low corrosivity, and convenient assembly in air.
A series of [6,6]-phenyl C61-butyric acid esters, including methanofullerene [6,6]-phenyl C61-butyric acid
methyl ester (PCBM) with different alkyl chain lengths (C1−C16) was synthesized from the reaction of C60
and alkyl 4-benzoylbutyrate p-tosylhydrazone in the presence of sodium methylate. The solubility of C60
derivatives in organic solvents increased with the increase in the length of alkyl substitutions. Photovoltaic
cells with these derivatives were fabricated with the structure of ITO/PEDT/MEH−PPV + C60 derivatives/Ba/Al. Device performances with such PCBM analogues were investigated and discussed in terms of Donor/Acceptor (D/A) phase separation and mobility of acceptor phase. The results clearly indicate that both interfacial
properties of the two phases (donor and acceptor) and mobility of electrons and holes within corresponding
phases play an important role in the efficiencies of PV cells. This study revealed that methanofullerenes
[6,6]-phenyl C61-butyric acid butyl ester, PCBB, possesses better photosensitivity than the PCBM, a widely
investigated and well-recognized C60 derivative for polymer PV cells The energy conversion efficiency reaches
2.84% for PCBB under AM1.5 illumination (78.2 mW/cm2), but 2.0% for PCBM fabricated in the same
conditions.
By blending poly(ethylene glycol) (PEG) into an electroluminescence (EL) polymer, significantly enhanced EL efficiency in a polymer light-emitting diode (PLED) with aluminum electrode was achieved. An orange-color-emitting PLED with 10 wt % PEG blending achieved device efficiencies exceeding 2.6 cd/A for a wide range of bias voltage, which is more than two orders of magnitude higher than that of a similar PLED without the PEG blending. The enhanced efficiency was a result of the reduction of electron injection barrier height at the cathode–polymer interface. It is believed that interfacial interaction that is specific to Al plays an important role in the enhancement mechanism.
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