Measuring the exciton diffusion length of C60 in organic planar heterojunction solar cells

Planar copper phthalocyanine (CuPc)/C60 heterojunction solar cells with a 2 nm layer of bathocuproine (BCP) inserted into the C60 layer were fabricated and characterized. The 2 nm BCP layer in the devices was used as an electronically selective sieve allowing the electron current through but blocking the excitons in the C60 layer. By combining the experimental results with the optical modeling, the effective triplet exciton diffusion length in C60 was confirmed to be 30–35 nm under the device working condition. We demonstrate a simple, useful method to determine the exciton diffusion lengths of organic electron acceptors.

[1]  Barry P Rand,et al.  4.2% efficient organic photovoltaic cells with low series resistances , 2004 .

[2]  Stephen R. Forrest,et al.  Mixed donor-acceptor molecular heterojunctions for photovoltaic applications. I. Material properties , 2005 .

[3]  Jeremy J. Baumberg,et al.  Polariton lasing by exciton-electron scattering in semiconductor microcavities , 2002 .

[4]  Robert L. Whetten,et al.  Photophysical properties of C60 , 1991 .

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

[6]  Yang Yang,et al.  Efficient Organic Heterojunction Photovoltaic Cells Based on Triplet Materials , 2005 .

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

[8]  Method of determining the exciton diffusion length using optical interference effect in Schottky diode , 2009 .

[9]  R. J. Bell,et al.  Optical properties of the metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the infrared and far infrared. , 1983, Applied optics.

[10]  L. Pfeiffer,et al.  Electron-polariton scattering, beneficial and detrimental effects , 2004 .

[11]  S. Forrest,et al.  Mixed donor-acceptor molecular heterojunctions for photovoltaic applications. II. Device performance , 2005 .

[12]  Stephen R. Forrest,et al.  Very-high-efficiency double-heterostructure copper phthalocyanine/C60 photovoltaic cells , 2001 .

[13]  C. S. Menon,et al.  Electrical conductivity studies and optical absorption studies in copper phthalocyanine thin films , 1995 .

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

[15]  A. M. Rao,et al.  Ellipsometric determination of the optical constants of C60 (Buckminsterfullerene) films , 1991 .

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

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

[18]  R. D. Gould,et al.  Dependence of the mobility and trap concentration in evaporated copper phthalocyanine thin films on background pressure and evaporation rate , 1986 .

[19]  Ching Wan Tang,et al.  Organic Schottky barrier photovoltaic cells based on MoOx/C60 , 2010 .

[20]  M. Dresselhaus,et al.  Role of molecular oxygen and other impurities in the electrical transport and dielectric properties of C{sub 60} films , 1997 .

[21]  D. L. Dexter.  A Theory of Sensitized Luminescence in Solids , 1953 .

[22]  Stephen R. Forrest,et al.  Transient analysis of organic electrophosphorescence: I. Transient analysis of triplet energy transfer , 2000 .

[23]  N. Yokoyama,et al.  DIELECTRIC-BASE TRANSISTORS WITH DOPED CHANNEL , 1997 .

[24]  Xudong Chen,et al.  Nondestructive evaluation of nanoscale structures: inverse scattering approach , 2010 .

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

[26]  M. Baldo,et al.  Simplified calculation of dipole energy transport in a multilayer stack using dyadic Green's functions. , 2007, Optics express.

[27]  Alan Sussman,et al.  Space‐Charge‐Limited Currents in Copper Phthalocyanine Thin Films , 1967 .