The effect of active layer thickness and composition on the performance of bulk-heterojunction solar cells

At present, bulk heterojunction polymer solar cells are typically fabricated with an active layer thickness of between 80 and 100nm. This active layer thickness has traditionally been chosen based on convenience and empirical results. However, a detailed study of the effects that active layer thickness has on the short circuit current and efficiency has not been performed for bulk heterojunction polymer solar cells so far. We demonstrate that the performance of these devices is highly dependent on the active layer thickness and, using a well established model for optical interference, we show that such effects are responsible for the variations in performance as a function of active layer thickness. We show that the ideal composition ratio of the donor and acceptor materials is not static, but depends on the active layer thickness in a predictable manner. A comparison is made between solar cells comprised of the donor materials regioregular poly(3-hexylthiophene) and poly(2-methoxy-5-(3′,7′-dimethyloctylo...

[1]  Vladimir Dyakonov,et al.  Influence of nanomorphology on the photovoltaic action of polymer–fullerene composites , 2004 .

[2]  C. Tang.  Two‐layer organic photovoltaic cell , 1986 .

[3]  David L. Carroll,et al.  High-efficiency photovoltaic devices based on annealed poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1- phenyl-(6,6)C61 blends , 2005 .

[4]  Christoph J. Brabec,et al.  Simulation of light intensity dependent current characteristics of polymer solar cells , 2004 .

[5]  Neil C. Greenham,et al.  PHOTOINDUCED ELECTRON TRANSFER FROM CONJUGATED POLYMERS TO CDSE NANOCRYSTALS , 1999 .

[6]  Stephen R. Forrest,et al.  Asymmetric tandem organic photovoltaic cells with hybrid planar-mixed molecular heterojunctions , 2004 .

[7]  C. Brabec,et al.  Effect of LiF/metal electrodes on the performance of plastic solar cells , 2002 .

[8]  A. Alivisatos,et al.  Hybrid Nanorod-Polymer Solar Cells , 2002, Science.

[9]  Sven Laux,et al.  Room-temperature deposition of indium tin oxide thin films with plasma ion-assisted evaporation , 1998 .

[10]  Christoph J. Brabec,et al.  Recombination and loss analysis in polythiophene based bulk heterojunction photodetectors , 2002 .

[11]  Niyazi Serdar Sariciftci,et al.  Effects of Postproduction Treatment on Plastic Solar Cells , 2003 .

[12]  Stephen R. Forrest,et al.  Small molecular weight organic thin-film photodetectors and solar cells , 2003 .

[13]  P. Blom,et al.  Unification of the hole transport in polymeric field-effect transistors and light-emitting diodes. , 2003, Physical review letters.

[14]  Xiong Gong,et al.  Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology , 2005 .

[15]  Valentin D. Mihailetchi,et al.  Device model for the operation of polymer/fullerene bulk heterojunction solar cells , 2005 .

[16]  N. Arnold,et al.  Modeling the optical absorption within conjugated polymer/fullerene-based bulk-heterojunction organic solar cells , 2003 .

[17]  Dieter Meissner,et al.  Nanoscale Morphology of Conjugated Polymer/Fullerene‐Based Bulk‐ Heterojunction Solar Cells , 2004 .

[18]  Richard H. Friend,et al.  General observation of n-type field-effect behaviour in organic semiconductors , 2005, Nature.

[19]  C. Brabec,et al.  Organic photovoltaic devices produced from conjugated polymer/methanofullerene bulk heterojunctions , 2001 .

[20]  V. Mihailetchi,et al.  Photocurrent generation in polymer-fullerene bulk heterojunctions. , 2004, Physical review letters.

[21]  Jenny Nelson,et al.  Diffusion-limited recombination in polymer-fullerene blends and its influence on photocurrent collection , 2003 .

[22]  C. Brabec,et al.  2.5% efficient organic plastic solar cells , 2001 .

[23]  Oliver Ambacher,et al.  Effects of solvent and annealing on the improved performance of solar cells based on poly(3-hexylthiophene): Fullerene , 2005 .

[24]  B. Kippelen.  Organic Photovoltaics , 2007, 2007 Conference on Lasers and Electro-Optics (CLEO).

[25]  Christoph J. Brabec,et al.  Charge recombination in conjugated polymer/fullerene blended films studied by transient absorption spectroscopy , 2003 .

[26]  Valentin D. Mihailetchi,et al.  Hole Transport in Poly(phenylene vinylene)/Methanofullerene Bulk‐Heterojunction Solar Cells , 2004 .

[27]  Michael D. McGehee,et al.  Conjugated Polymer Photovoltaic Cells , 2004 .

[28]  L. S. Roman,et al.  Modeling photocurrent action spectra of photovoltaic devices based on organic thin films , 1999 .

[29]  J. Hummelen,et al.  Polymer Photovoltaic Cells: Enhanced Efficiencies via a Network of Internal Donor-Acceptor Heterojunctions , 1995, Science.

[30]  Yang Yang,et al.  High-efficiency solution processable polymer photovoltaic cells by self-organization of polymer blends , 2005 .