Small-Molecule Bulk Heterojunctions: Distinguishing Between Effects of Energy Offsets and Molecular Packing on Optoelectronic Properties

We report on the dependence of time-resolved photoluminescence (PL) and photocurrent in small-molecule bulk heterojunctions on the donor–acceptor (D/A) LUMO offset, D/A separation, and acceptor domain structure. We chose a high-performance functionalized fluorinated anthradithiophene (ADT) derivative, ADT-TES-F, as the donor and two other fluorinated ADT derivatives, ADT-R-F (where R is a variable side group), as well as two functionalized fluorinated pentacene (Pn) derivatives, Pn-R-F8, as acceptors. The choice of ADT and Pn acceptors enabled us to separate the effects of the D/A LUMO offset, which was approximately zero in the case of ADT acceptors and ∼0.55 eV in the case of Pn acceptors, from those of molecular packing on the optoelectronic properties. The acceptor side groups R were chosen based on (i) packing motifs in the solid state and (ii) size, to achieve different D/A separations at the D/A interface. Addition of an ADT-R-F acceptor to the ADT-TES-F donor introduced disorder, which resulted in...

[1]  A. J. Heeger,et al.  Temperature-Independent Photoconductivity in Thin Films of Semiconducting Polymers: Photocarrier Sweep-Out Prior to Deep Trapping , 1998 .

[2]  W E Moerner,et al.  Organic photorefractives: mechanisms, materials, and applications. , 2004, Chemical reviews.

[3]  Stephen R. Forrest,et al.  Separation of geminate charge-pairs at donor–acceptor interfaces in disordered solids , 2004 .

[4]  Christopher R. Swartz,et al.  Synthesis and characterization of electron-deficient pentacenes. , 2005, Organic letters.

[5]  John E. Anthony,et al.  Optical and transient photoconductive properties of pentacene and functionalized pentacene thin films: Dependence on film morphology , 2005 .

[6]  John E Anthony,et al.  Functionalized acenes and heteroacenes for organic electronics. , 2006, Chemical reviews.

[7]  Ifor D. W. Samuel,et al.  Organic semiconductor lasers. , 2007 .

[8]  John E. Anthony,et al.  High-mobility spin-cast organic thin film transistors , 2008 .

[9]  Weimin Zhang,et al.  Charge carrier formation in polythiophene/fullerene blend films studied by transient absorption spectroscopy. , 2008, Journal of the American Chemical Society.

[10]  Sankar Subramanian,et al.  Chromophore fluorination enhances crystallization and stability of soluble anthradithiophene semiconductors. , 2008, Journal of the American Chemical Society.

[11]  John E. Anthony,et al.  Organic Single-Crystal Field-Effect Transistors of a Soluble Anthradithiophene , 2008 .

[12]  John E. Anthony,et al.  Photoconductivity in organic thin films: From picoseconds to seconds after excitation , 2008 .

[13]  John E. Anthony,et al.  Contact-induced crystallinity for high-performance soluble acene-based transistors and circuits. , 2008, Nature materials.

[14]  John E. Anthony,et al.  Optical, Fluorescent, and (Photo)conductive Properties of High-Performance Functionalized Pentacene and Anthradithiophene Derivatives , 2009 .

[15]  Z. Bao,et al.  Correlating carrier type with frontier molecular orbital energy levels in organic thin film transistors of functionalized acene derivatives. , 2009, Journal of the American Chemical Society.

[16]  John E. Anthony,et al.  Influence of organic semiconductor-metal interfaces on the photoresponse of functionalized anthradithiophene thin films , 2009 .

[17]  John E. Anthony,et al.  Organic semiconductor composites: influence of additives on the transient photocurrent , 2009 .

[18]  John E. Anthony,et al.  Soluble n-type pentacene derivatives as novel acceptors for organic solar cells , 2009 .

[19]  Howard E. Katz,et al.  Thin-Film Organic Electronic Devices , 2009 .

[20]  A. Heeger,et al.  Semiconducting polymers: the Third Generation. , 2010, Chemical Society reviews.

[21]  Thomas Strobel,et al.  Role of the Charge Transfer State in Organic Donor–Acceptor Solar Cells , 2010, Advanced materials.

[22]  David Hofer,et al.  Aggregate formation and its effect on (opto)electronic properties of guest-host organic semiconductors , 2010 .

[23]  Tracey M. Clarke,et al.  Charge photogeneration in organic solar cells. , 2010, Chemical reviews.

[24]  J. Pflaum,et al.  Charge Separation at Molecular Donor–Acceptor Interfaces: Correlation Between Morphology and Solar Cell Performance , 2010, IEEE Journal of Selected Topics in Quantum Electronics.

[25]  J. Brédas,et al.  Steric control of the donor/acceptor interface: implications in organic photovoltaic charge generation. , 2011, Journal of the American Chemical Society.

[26]  Antonio Facchetti,et al.  π-Conjugated Polymers for Organic Electronics and Photovoltaic Cell Applications† , 2011 .

[27]  John E. Anthony,et al.  Temperature dependence of exciton and charge carrier dynamics in organic thin films , 2011 .

[28]  B. Purushothaman.  PARTIALLY HALOGENATED ACENES AND HETEROACENES FOR ORGANIC ELECTRONICS , 2011 .

[29]  Frédéric Laquai,et al.  Ultrafast exciton dissociation followed by nongeminate charge recombination in PCDTBT:PCBM photovoltaic blends. , 2011, Journal of the American Chemical Society.

[30]  Andrew J. Moad,et al.  Controlling the Microstructure of Solution-Processable Small Molecules in Thin-Film Transistors through Substrate Chemistry , 2011 .

[31]  A. Salleo,et al.  Effect of Acene Length on Electronic Properties in 5‐, 6‐, and 7‐Ringed Heteroacenes , 2011, Advanced materials.

[32]  Thuc-Quyen Nguyen,et al.  Small Molecule Solution-Processed Bulk Heterojunction Solar Cells† , 2011 .

[33]  John E. Anthony,et al.  Energy Transfer and Exciplex Formation and Their Impact on Exciton and Charge Carrier Dynamics in Organic Films , 2011 .

[34]  David Beljonne,et al.  Electronic Processes at Organic−Organic Interfaces: Insight from Modeling and Implications for Opto-electronic Devices† , 2011 .

[35]  Wei Lin Leong,et al.  Solution-processed small-molecule solar cells with 6.7% efficiency. , 2011, Nature materials.

[36]  Matthias Weil,et al.  Interrelation between Crystal Packing and Small‐Molecule Organic Solar Cell Performance , 2012, Advanced materials.

[37]  F. Wudl,et al.  Top-down meets bottom-up: organized donor–acceptor heterojunctions for organic solar cells , 2012 .

[38]  C. Deibel,et al.  Direct and charge transfer state mediated photogeneration in polymer–fullerene bulk heterojunction solar cells , 2012, 1204.4788.

[39]  Thuc‐Quyen Nguyen,et al.  Quantification of Geminate and Non‐Geminate Recombination Losses within a Solution‐Processed Small‐Molecule Bulk Heterojunction Solar Cell , 2012, Advanced materials.

[40]  John E. Anthony,et al.  Formation of the Donor–Acceptor Charge-Transfer Exciton and Its Contribution to Charge Photogeneration and Recombination in Small-Molecule Bulk Heterojunctions , 2012 .

[41]  K. Arlauskas,et al.  Photogeneration and recombination of charge carrier pairs and free charge carriers in polymer/fullerene bulk heterojunction films , 2012 .

[42]  D. Laird,et al.  Two-step charge photogeneration dynamics in polymer/fullerene blends for photovoltaic applications , 2012 .

[43]  T. Savenije,et al.  Mechanism of Mobile Charge Carrier Generation in Blends of Conjugated Polymers and Fullerenes: Significance of Charge Delocalization and Excess Free Energy , 2012 .

[44]  Gregory C. Welch,et al.  Photoinduced charge generation in a molecular bulk heterojunction material. , 2012, Journal of the American Chemical Society.

[45]  Paul L. Burn,et al.  Kinetics of charge transfer processes in organic solar cells: Implications for the design of acceptor molecules , 2012 .

[46]  Thomas Kirchartz,et al.  Competition between the charge transfer state and the singlet states of donor or acceptor limiting the efficiency in polymer:fullerene solar cells. , 2012, Journal of the American Chemical Society.

[47]  Chris Groves,et al.  The relative importance of domain size, domain purity and domain interfaces to the performance of bulk-heterojunction organic photovoltaics , 2012 .

[48]  Yongfang Li,et al.  Small molecule semiconductors for high-efficiency organic photovoltaics. , 2012, Chemical Society reviews.

[49]  Junping Du,et al.  On the energetic dependence of charge separation in low-band-gap polymer/fullerene blends. , 2012, Journal of the American Chemical Society.

[50]  G. Cerullo,et al.  Hot exciton dissociation in polymer solar cells. , 2013, Nature materials.

[51]  Fangli Zhao,et al.  Manipulating open-circuit voltage in an organic photovoltaic device via a phenylalkyl side chain. , 2013, Chemical communications.

[52]  D. Ginger,et al.  Photoinduced Hole Transfer Becomes Suppressed with Diminished Driving Force in Polymer‐Fullerene Solar Cells While Electron Transfer Remains Active , 2013 .

[53]  Iain McCulloch,et al.  Charge-Transfer State Dynamics Following Hole and Electron Transfer in Organic Photovoltaic Devices. , 2013, The journal of physical chemistry letters.

[54]  Adam P. Willard,et al.  Hot charge-transfer excitons set the time limit for charge separation at donor/acceptor interfaces in organic photovoltaics. , 2013, Nature materials.

[55]  Wei Zhang,et al.  Mechanism of Primary Charge Photogeneration in Polyfluorene Copolymer/Fullerene Blends and Influence of the Donor/Acceptor Lowest Unoccupied Molecular Orbital Level Offset , 2013 .

[56]  Brian F. G. Johnson,et al.  Charge carrier dynamics in organic semiconductors and their donor-acceptor composites: Numerical modeling of time-resolved photocurrent , 2013 .

[57]  Gilles Horowitz,et al.  Templating and charge injection from copper electrodes into solution-processed organic field-effect transistors. , 2013, ACS applied materials & interfaces.

[58]  Naichia Yeh,et al.  Organic solar cells: Their developments and potentials , 2013 .

[59]  Oksana Ostroverkhova,et al.  Handbook of organic materials for optical and (opto)electronic devices , 2013 .