Investigating ultrafast carrier dynamics in perovskite solar cells with an extended π-conjugated polymeric diketopyrrolopyrrole layer for hole transportation.

Here, we show a new diketopyrrole based polymeric hole-transport material (PBDTP-DTDPP, (poly[[2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-]pyrrole-1,4-diyl]--[[2,2'-(4,8-bis(4-ethylhexyl-1-phenyl)-benzo[1,2-:4,5-']dithiophene)bis-thieno[3,2-]thiophen]-5,5'-diyl]])) for application in perovskite solar cells. The material performance was tested in a solar cell with an optimized configuration, FTO/SnO/perovskite/PBDTP-DTDPP/Au, and the device showed a power conversion efficiency of 14.78%.

Minimizing Trap Charge Density towards an Ideal Diode in Graphene-Silicon Schottky Solar Cell.

Photovoltaic device performance of graphene/n-Si Schottky diodes is largely affected by inhomogeneous oxide formation at the interface that suppresses the tunneling current of injected and photoexcited charges. The accumulated trap charges at low current induce charge recombination at the interface and degrade the ideality factor of the diode and the fill factor (FF) of the solar cell. This consequently gives rise to a nonlinear current-voltage ( I- V) feature in solar cells, commonly known as an S-shaped kink, which can be engineered by optimizing the interface barrier thickness or by increasing the carrier mobility.

Excitation Intensity Dependent Carrier Dynamics of Chalcogen Heteroatoms in Medium-Bandgap Polymer Solar Cells.

The excitation intensity dependent carrier dynamics of blends with PC[70]BM of three new medium-band gap conjugated polymers with central chalcogen heteroatoms, PBDTfDTBX (X = O, T(Sulphur), Se) were studied. The PBDTfDTBX polymers (Poly[4,8-bis(5-(2-butyloctyl)thiophene-2-yl)benzo[1,2-b;4,5-b']dithiophene-alt-4,7-bis(4-(2-ethylhexyl)-2-thienyl)-dithieno[3',2':3,4;2″,3″:5,6]benzo[1,2-c][1,2,5] furazan or thiadiazole or selenadiazole]) have symmetrical structures but exhibit different solar cell performances. In this study, we determined how the photogenerated charge carrrier dynamics of the PBDTfDTBX:PC[70]BM blends varies with the heteroatom by performing transient absorption measurements at various excitation intensities.

Phosphorescent blue organic light-emitting diodes with new bipolar host materials.

We report narrow band gap bipolar host materials, CbPr-3 (9,9'-[(3,3'-Biphenyl-3.3'-yl-bipyridine)-1,3-biphenyl]bis-9H-carbazole) and Bim-4 (9,9'-[5-(1-phenyl-1H-benzimadazol-2yl)-1,3-phenylene] bis-9H-carbazole), for blue phosphorescent OLEDs application. These two bipolar hosts have high triplet energy of > 2.

Lithium barium silicate, Li(2)BaSiO(4), from synchrotron powder data.

The structure of lithium barium silicate, Li(2)BaSiO(4), has been determined from synchrotron radiation powder data. The title compound was synthesized by high-temperature solid-state reaction and crystallizes in the hexagonal space group P6(3)cm. It contains two Li atoms, one Ba atom (both site symmetry .

Photoluminescent and decay behaviors of Mn2+ and Ce3+ coactivated MgSiN2 phosphors for use in light-emitting-diode applications.

We examined the photoluminescent behaviors of MgSiN2:Mn2+ and MgSiN2:Ce3+,Mn2+ phosphors for use in white-light-emitting diodes. The red emission from MgSiN2:Mn2+ phosphors consisted of two Gaussian components, P1 from a single Mn2+ ion and P2 from either Mn2+ pairs or clusters. Decay analysis based on the Yokota and Tanimoto equation identified long decay for P1 and fast decay for P2.

Systematic control of experimental inconsistency in combinatorial materials science.

We developed a method to systematically control experimental inconsistency, which is one of the most troublesome and difficult problems in high-throughput combinatorial experiments. The topic of experimental inconsistency is never addressed, even though all scientists in the field of combinatorial materials science face this very serious problem. Experimental inconsistency and material property were selected as dual objective functions that were simultaneously optimized.

Search for new red phosphors using genetic algorithm-assisted combinatorial chemistry.

A genetic algorithm was employed in association with high-throughput synthesis and characterization in an attempt to search for red phosphors with high photoluminescent intensity. A tetravalent manganese-doped alkali earth germanium oxide system, with an emission color close to a desirable deep red, was screened with the assistance of a genetic algorithm to pinpoint the phosphor exhibiting the highest photoluminescence. As the genetic algorithm was in progress, the PL intensity increased and maximized in the fourth generation.