Determination of carrier mobility in MEH-PPV thin-films by stationary and transient current techniques

Abstract

Charge transport and shelf-degradation of MEH-PPV thin-films were investigated through stationary (e.g. current versus voltage -JxV) and transient (e.g. Time-of-Flight -ToF, Dark-Injection Space-Charge-Limited Current -DI-SCLC, Charge Extraction by Linearly Increasing Voltage -CELIV) current techniques. Charge carrier mobility in nanometric films was best characterized through JxV and DI-SCLC. It approaches 10 − 6 cm 2 /Vs under a SCLC regime with deep traps for light-emitting diode applications. ToF measurements performed on micrometric layers (i.e.~3 μm) confirmed studies in 100 nm-thick films as deposited in OLEDs. All results were comparable to a similar poly(para-phenylene vinylene) derivative, MDMO-PPV. Electrical properties extracted from thin-film transistors demonstrated mobility dependence on carrier concentration in the channel (~10 − 7 -10 − 4 cm 2 /Vs). At low accumulated charge levels and reduced free carrier concentration, a perfect agreement to the previously cited techniques was observed. Degradation was verified through mobility reduction and changes in trap distribution of states.

Complementing Graphenes: 1D Interplanar Charge Transport in Polymeric Graphitic Carbon Nitrides

“…[ 36 ] In order to elucidate the question of dimensionality further, we consider the limiting cases of the geminate process by allowing for bimolecular recombination and solving Equation ( 2) numerically. The results are shown in Figure 4 a,b for D = 1,2,3, where hopping rates obtained from the respective fi ts have been used (see Table S1, Supporting Information).…”

Bulk- and layer-heterojunction phototransistors based on poly [2-methoxy-5-(2′-ethylhexyloxy-p-phenylenevinylene)] and PbS quantum dot hybrids

“…The regular-shaped interface has two influences, being good for carrier transport (improved order degree of channel) but being harmful to charge separation (b is as low as À0.18). The MEH-PPV hole mobility is of the order of 10 À2 -10 À6 cm 2 V À1 s À1 , 28,31 while that of the QD FET is $10 cm 2 V À1 s À1 , 7 indicating that the holes in the QD layer are transported more effectively than in MEH-PPV. Thus, the measured mobility (36 cm 2 V À1 s À1 ) is mainly the contribution of the hole transport in the QD layer, and is also a reasonable value for mobility in QD FETs, according to a previous report.…”

Role of Polymer in Hybrid Polymer/PbS Quantum Dot Solar Cells

“…On the contrary the combination of narrow-bandgap polymers, such as LBPP-4 and PDPP3T, with PbS QDs leads to less efficient electron/exciton transfer and, in addition, funnels the population of shallow midgap trap states on PbS QDs.Finally it is worth noting that, while the mobility of polymers is very important for charge transport and efficiency of polymer/fullerene bulk heterojunction solar cells, in our system we cannot find a correlation between the mobility of polymers in the HCs and the final device performance. Indeed, the low band gap PDPP3T and wide band gap P3HT feature similar mobility 21,36 although performing very differently in HC solar cells; on the contrary MEH-PPV and P3HT have very different mobility[36][37][38][39] and similar HC based photovoltaic performances. Even if further studies should clarify this peculiarity, we suggest that the photovoltaic performance in HCs…”