Impact of molecular weight on charge carrier dissociation in solar cells from a polyfluorene derivative

Abstract

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The effect of the molecular weight of poly[9,9-didecanefluorene-alt-(bis-thienylene) benzothiadiazole] (PF10TBT) on the photovoltaic performance of fullerene-based bulk heterojunction solar cells is investigated. An increase in molecular weight of two orders of magnitude results in a 30% increase of the short-circuit current and a rise of the fill factor from 0.45 to 0.63. Electron and hole transport are found to be virtually unaffected by changing molecular weight, which means that space-charge effects do not play a role in low molecular weight devices. Using optical modeling and numerical device simulations, we demonstrate that at low molecular weight the efficiency is mainly limited by a short lifetime of bound electron-hole pairs. This short lifetime prohibits efficient dissociation and is attributed to a deficiency in phase separation for low molecular weights.

All-solution processed polymer light-emitting diodes with air stable metal-oxide electrodes

“…with J the current density, e 0 the permittivity of vacuum, e the relative dielectric constant of the polymer, l p and l n the hole and electron mobility, B the bimolecular recombi- /Vs, in agreement with previous determinations [22]. Furthermore, a decrease in the turn-on voltage is observed, as previous publications have shown as well [3].…”

A facile route to inverted polymer solar cells using a precursor based zinc oxide electron transport layer

“…Furthermore, optical absorption simulations based on the transfer matrix formalism have been performed on the two structures for the PF10TBT:PCBM blend [31][32][33][34]. The optical constants needed for this simulation were obtained with variable angle spectroscopic ellipsometry [24,35]. The layer thicknesses of the ZnO and MoO 3 layers for this simulation have been defined as 20 and 10 nm, respectively.…”

Hole-enhanced electron injection from ZnO in inverted polymer light-emitting diodes

“…Here, we fabricated conventional and inverted PLEDs with PF10TBT and IDT-BT as the active layers. The LUMO of PF10TBT is 3.4 eV [30], which reduces the electron injection barrier in an inverted PLED to 0.8 eV. The LUMO of IDT-BT is located at 3.6 eV, obtained by adding the optical band gap to the experimentally determined HOMO [31,32].…”