Impact of molecular weight on charge carrier dissociation in solar cells from a polyfluorene derivative
de Boer, B.
TNO Industrie en Techniek
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. © 2009 Elsevier B.V. All rights reserved.
High Tech Systems & Materials
To reference this document use:
Bulk heterojunction solar cells
Charge carrier dissociation
Low molecular weight
Numerical device simulation
Orders of magnitude
Space charge effects
Solar power generation
Organic Electronics: physics, materials, applications, 10 (7), 1275-1281