Additives such as solvents, nano particles and ionic lquids were found to be very effective in improving PSS:PEDOT polymer properties. However, small molecules have strong tendency to diffuse, especially at working condition when temperature is higher. Dangling structure copolymer, such as Nafion and Flemion and/or their chemical derivatives may be better replacements. PSS:PEDOT:Flemion was studied using multiscale analysis and dissipative particle dynamic (DPD) simulations. The DPD inter particle repulsion parameters and intramolecular bonding parameters were obtained by reverse mapping of a series of molecular dynamic simulations similar to that used in the earlier contributions. Flemion copolymer was found to form strong link to both PEDOT and PSS chains. While, causing similar effect on PEDOT polymer chains as pfi (Nafion) copolymer, increasing PSS monomer-monomer bending angle and repulsion among monomers it does not cause strong phase separation. DFT simulation indicates, Flemion can form strong hydrogen bond complex with PSS:PEDOT, and lower their HOMO energy as well. Flemion may be candidate as an additive to manipulate PEDOT concentration profile in selforganized PSS:PEDOT:pfi film.
Dimethyl sulfoxide (DMSO) and ethylene glycol (EG) solvent treatment of conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were studied using multiscale analysis and dissipative particle dynamic (DPD) simulations. The DPD inter particle repulsion parameters and intramolecular bonding parameters were obtained by reverse mapping of a series of molecular dynamic simulations similar to that used in the earlier contributions. The solvent treatments were found to cause three effects on PEDOT polymer chains at molecular level, increasing rigidity in monomer-monomer bending, decreasing rigidity in monomer-monomer stretching, and decreasing repulsion among monomers. Consequently, these effects lead to PEDOT micro phase segregation and semi-ordered local region formation within and/or between polymer chains. Since the reduction of repulsion among PEDOT monomers can only be caused from selective π−π staking, the formation of these semi-ordered (crystal like) local region may allow charges to bypass local disordered region within the polymer chain and hopping between individual polymer chains, thus, enhance electrical conductivity in orders of magnitude. The implication on PSS:PEDOT:PFI are discussed.
The vertically self-organized concentration profile of the PSS:PEDOT:PFI layer from mesoscale DPD simulations presented in the previous contribution were inversely mapped back into atomistic scale. DFT quantum calculations were then performed to understand the nature of the formation of the PFI:PSS:PEDOT complex. Hydrogen bond bonding energy and deprotonation energy were obtained accordingly. The charge states of PSS polymer chain in this complex and its effects on the HOMO-LUMO (the work function) were discussed. The DFT quantum calculation revealed the formation of complex hydrogen bonding networks leading to the formation of super PFI:PSS:PEDOT structure. PFI was found to be a stronger H donor than PSS. The adding of PFI was found to have the effect of lowering the energy of PSS chain, as the result the HOMO of the PFI:PSS:PEDOT ternary structure was found to be -5.35 eV, lower than the original PSS:PEDOT binary structure. The increasing of the work function from the bottom to the top of the film can therefore be understood as the result of the combining effects of increasing PSS:PEDOT and PFI:PSS ratio in the vertical direction induced by PFI led phase segregation.
The role of MAPbI3 perovskite crystal facet surface property, surface cohesion, was investigated in this study. The interaction energy of as grown MAPbI3 perovskite crystal facet (002), (110), (112) and (200) with organic PSS-PEDOT, PCBM and Sprio-OMeTAD molecules were obtained using molecular dynamics simulations. The results indicated that these three molecules can interact well with all four common facets of MAPbI3 crystal producing negative interactive energies. The interacting between Sprio-OMeTAD molecule and the MAPbI3 perovskite crystal surface is the strongest producing the lowest interactive energy. While PCBM is the weakest and PSS-PEDOT in between. The interaction energies of these three molecules show similar preferential orders, they are (112), (002), (200) and (110) respectively. In the PCBM case, energy differences among facet surfaces (002), (110) and (200) are small when compare with surface (112). Solar cells made from tailored crystals with large (112)/(002) surfaces can be expected to have better crystal-PEDPT:PSS contact therefore, better hole injection efficiency. Same goes to the Sprio-OMeTAD and PCBM where higher electron extraction efficiency can be expected.
Conducting polymers, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been widely used as the hole injection layer (HIL) in many applications. However, in OLEDs the commonly used PEDOT:PSS has been found to have serious problems due to its inefficient holeinjection, inefficient electron-blocking, and substantial quenching of excitons close to the PEDOT:PSS. In the literature, tetrafluoroethylene-perfluoro-3,6-dioxa-4-methyl-7-octene-sulfonic acid copolymer, one of perfluorinated ionomers (PFI), was introduced into the PEDOT:PSS layer to develop a gradient work function (WF) by self-organization of the PFI. In this contribution, the self-organized gradient effect of this novel PEDOT:PSS:PFI layer were studied using multiscale analysis and dissipative particle dynamics (DPD) simulation. The DPD inter particle repulsion parameters and intramolecular bonding parameters were obtained by reverse mapping of a series of molecular dynamics simulations similar to that used in the earlier contributions. The calculated Flory-Huggins parameters indicated that the Nafion portion of the copolymer attracts PSS while the entire PFI molecule repulses PEDOT, which results in a PFI rich interface and a vertical gradient concentration distribution of PEDOT along the vertical direction of the film layer.
The influence of micro phase behavior on the charge transfer at the interface between
PEDOT:PSS and P3HT:PCBM layers was studied using multiscale analysis. Calculated Flory-
Huggins parameters indicated that the PEDOT attracts P3HT and repulses PCBM that agrees well
with the experimental observation of the development of P3HT rich interface during the BHJ
layer formation. Based on the calculated Flory-Huggins parameters, mesoscale DPD simulations
were conducted for PEDOT:PSS and P3HT:PCBM layers. Results were mapped to the CG (coarse
grained) and then atomistic scales where atomistic details of the interface were studied. The
density of nonbonding close contacts including that from reorientation between PEDOT and
P3HT was quantified, vibronic coupling and carrier transfer efficiency were discussed.
Exciton transport plays an important role in the overall exciton dissociation process and must be optimized to yield high efficient OPV device. In this contribution, the influence of solvents and the nanoscale phase separations they caused on the glass transition temperatures (Tg) of P3HT-PCBM mixture were studied by reverse mapping mesoscale simulation results back to the molecular dynamics. Glass transition temperatures of P3HT-PCBM without solvent and with chloroform, dichlorobenzene, and chlorobenzene were obtained. Diffusion and reorientation ability of molecules and their subgroups at the temperature near Tg were also discussed.
Solvents are often used in the active layer formation process in many photonic applications such as organic solar cell, organic led, organic wavelength conversion and photorefractive materials. In this contribution, multiscale modeling and simulation was used to reveal phase separation in P3HT-PCBM at mesoscale level due to attractionrepulsion between different organic functional groups of active ingredient molecules and solvent molecules. Force field parameters for mesoscale calculation were obtained from dynamic mapping of results from molecular dynamic simulations. DFT calculation was used to describe energy changes of active ingredient molecules due to surrounded residual solvent molecules. The simulation results from no solvent, chloroform, dichlorobenzene and chlorobenzene cases indicated that chlorobenzene exhibits strong attraction with fullerene of PCBM and strong repulsion with all the other functional groups, therefore leads to least phase segregation. DFT calculation showed that residual solvent molecules can slightly lower the energy but do not alter the value of band gap.
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