Polyfluorene copolymer based bulk heterojunction solar cells

Yohannes, Teketel; Zhang, Fengling; Svensson, Mattias; Hummelen, Jan C.; Andersson, Mats R.; Inganäs, Olle

doi:10.1016/s0040-6090(03)01348-8

Cited by 53 publications

(34 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Polyfluorene copolymers have shown to be suitable candidates for efficient solar cells [3][4][5]. A promising power conversion efficiency of 4.2% has been reported for a system of poly[9,9-didecanefluorene-alt-(bis-thienylene) benzothiadiazole] (PF10TBT) and [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM) [6].…”

Section: Introductionmentioning

confidence: 99%

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

Moet

Lenes

Kotlarski

et al. 2009

Organic Electronics

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

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

Moet

Lenes

Kotlarski

et al. 2009

Organic Electronics

View full text Add to dashboard Cite

show abstract

“…This particular blend and similar materials have been used in prototype devices yielding power conversion efficiencies of more than 2% under AM 1.5 illumination. 8,19) In the prototype photovoltaic cells, the simplest device structure consisting of Al/blend/ITO, is improved by insertion of a thin LiF layer between Al and the blend and a PEDOT-PSS layer between the blend and the ITO resulting in Al/LiF/active layer/PEDOT-PSS/ITO. 8,19) The use of both LiF and PEDOT-PSS in this way has proven effective in photovoltaic cells 20) and polymer light emitting diodes.…”

Section: Introductionmentioning

confidence: 99%

Photoelectron Spectroscopy of the Contact between the Cathode and the Active Layers in Plastic Solar Cells: The Role of LiF

Jönsson

Carlegrim

Zhang

et al. 2005

Jpn. J. Appl. Phys.

109

View full text Add to dashboard Cite

The surfaces and electrode interfaces of a polymer blend used in prototype solar cells have been characterized with photoelectron spectroscopy. The polymer blend in question is a 1 : 4 mixture of APFO-3 : PCBM. Based on surface analysis of the pristine film we can conclude that the surface of the blend is a 1 : 1 mixture of APFO-3 and PCBM. The electrode systems studied are the widely used Al and Al/LiF contacts. LiF prevents formation at the Al/organic interface of Al-organic complexes that destroy the -conjugation. In addition to this, there are two other beneficial, thickness dependent, effects. Decomposition of LiF occurs for thin enough layers in which the LiF species are in contact with both the organic film and the Al atoms, which creates a low workfunction contact. For thicker (multi)layers, the dipole formed at the LiF/organic interface is retained as no decomposition of the LiF occurs upon Al deposition.

show abstract

“…In all diodes, indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene) (PEDOT)-poly(styrenesulfonate) (PSS) are used as the bottom electrodes, and PEO/Al or Al are used as the top electrodes. The active layer is the mixing poly((2,7-(9-(2′-ethylhexyl)-9-hexyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole))-co-(2,7-(9-(2′-ethylhexyl)-9-hexyl-fluorene)-alt-2,5-thiophene)) APFO-5(LBPF3), [22][23][24] and [6,6]-phenyl-C 61 -butyric acid methylester (PCBM) in a stoichiometry of 1:4 (by weight). For comparison, all diodes were prepared and analyzed under the same conditions.…”

mentioning

confidence: 99%

Enhancing the Photovoltage of Polymer Solar Cells by Using a Modified Cathode

2007

View full text Add to dashboard Cite

Inexpensive solar cells with a low energy budget are interesting due to the need for alternative energy sources in the future.[1] Organic solar cells may become a low-cost alternative to Si-based solar cells because they are low weight, flexible, and could be produced by roll-to-roll printing techniques for large-area deposition. [2][3][4] Polymer solar cells are still hindered by their low efficiency, measured by the multiplication of short-circuit current (J sc ), open-circuit voltage (V oc ), and fill factor (FF) under solar illumination. J sc depends on the optical and electrical properties of the active layer, such as, absorption spectrum and charge mobility. V oc is proportional to the energy gap between the highest occupied molecular orbital (HOMO) of the donor and the lowest unoccupied molecular orbital (LUMO) of the acceptor, but also influenced by the work function difference between electrodes as well as the thickness of the active layers. It is hard to increase V oc and J sc simultaneously in polymer solar cells, because larger photocurrents require a low bandgap absorber for maximum overlap with the solar spectrum, but to enhance V oc a high bandgap absorber is needed. It is common to use a thin layer of LiF between the active layer and the cathode to improve the V oc in polymer solar cells. [5][6][7][8] The role of the submonolayer of LiF has been suggested to be that of protecting the organic layer during metal deposition, modifying the work function of the cathode, and/ or introducing a dipole at the cathode interface, affecting charge injection. [9][10][11][12][13] The possibility to use roll-to-roll printing techniques is the biggest advantage of polymer electronic devices compared with their inorganic counterparts. However, LiF is vapor deposited in vacuum and is impossible to use in printing techniques.In order to increase V oc recently many efforts have been made to build tandem cells. The V oc is increased by stacking two cells on top of each other. [14][15][16][17][18][19] However, the significant loss of J sc makes the overall performance lower than that of a single cell. [19] So far few polymer tandem cells give higher efficiency than single cells. [18] In addition, the procedure to build tandem cells is very complicated involving multilayer deposition both via a solution process and a vapor process in vacuum, [18,19] which is not easy in printing methods.Here, we report a simple method to increase the V oc up to 200 mV and the power conversion efficiency (PCE) by 50 %, by using a thin layer of poly(ethylene oxide) (PEO) to modify the cathode in polymer solar cells. It was reported that a thin layer of PEO between the active layer and the Al or LiF/Al cathode improves the performance of polymer light-emitting diodes (PLED).[20] An enhanced photocurrent of solar cells based on poly[2-methoxy-5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene] by blending a small amount of PEO and LiCF 3 SO 3 into the active layer was also demonstrated. [21] In this Communication, we demonstrate that a thin layer o...

show abstract

Polyfluorene copolymer based bulk heterojunction solar cells

Cited by 53 publications

References 9 publications

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

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

Photoelectron Spectroscopy of the Contact between the Cathode and the Active Layers in Plastic Solar Cells: The Role of LiF

Enhancing the Photovoltage of Polymer Solar Cells by Using a Modified Cathode

Contact Info

Product

Resources

About