Organic Photovoltaic Cells Based on a Medium-Bandgap Phosphorescent Material and C60

Organic photovoltaic (OPV) cells using a medium-bandgap phosphorescent material of bis(1,2-dipheny1-1H-benzoimidazole) iridium (acetylacetonate) [(pbi)2Ir(acac)] as an electron-donating layer were fabricated. An S-shaped kink was observed in the current–voltage curves with the increase in (pbi)2Ir(acac) thickness. Two ways of using different hole transport layers to reduce interfacial energy step and doping to improve charge carrier mobility were used to investigate the origin of the kink. The results showed that this anomalous feature is due to the presence of large interfacial energy step between the anode/donor-interface and the low hole mobility of (pbi)2Ir(acac). An improved power conversion efficiency of 2.23% under AM 1.5 solar illumination at an intensity of 100 mW/cm2 was obtained using N,N′-bis-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine to minimize the energy barrier for charge injection.

[1]  R. Friend,et al.  The Origin of Collected Charge and Open‐Circuit Voltage in Blended Polyfluorene Photovoltaic Devices , 2004 .

[2]  Karl Leo,et al.  Influence of Hole‐Transport Layers and Donor Materials on Open‐Circuit Voltage and Shape of I–V Curves of Organic Solar Cells , 2011 .

[3]  Yuh-Sheng Wen,et al.  Highly Phosphorescent Bis-Cyclometalated Iridium Complexes Containing Benzoimidazole-Based Ligands , 2004 .

[4]  Fred Wudl,et al.  Organic Electronics: From Materials to Devices , 2009 .

[5]  N. E. Coates,et al.  Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Processing , 2007, Science.

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

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

[8]  Guillermo C Bazan,et al.  Streamlined microwave-assisted preparation of narrow-bandgap conjugated polymers for high-performance bulk heterojunction solar cells. , 2009, Nature chemistry.

[9]  Thuc‐Quyen Nguyen,et al.  A Low Band Gap, Solution Processable Oligothiophene with a Diketopyrrolopyrrole Core for Use in Organic Solar Cells , 2008 .

[10]  V. Roy,et al.  Improving efficiency of organic photovoltaic cells with pentacene-doped CuPc layer , 2007 .

[11]  Gang Li,et al.  Highly efficient solar cell polymers developed via fine-tuning of structural and electronic properties. , 2009, Journal of the American Chemical Society.

[12]  Wei You,et al.  Fluorine substituted conjugated polymer of medium band gap yields 7% efficiency in polymer-fullerene solar cells. , 2011, Journal of the American Chemical Society.

[13]  Junsheng Yu,et al.  Effect of buffer layers on the performance of organic photovoltaic cells based on copper phthalocyanine and C60 , 2010 .

[14]  Yang Yang,et al.  Dipole induced anomalous S-shape I-V curves in polymer solar cells , 2009 .

[15]  D. Rauh,et al.  S-shaped current-voltage characteristics of organic solar devices , 2010, 1005.5669.

[16]  Norbert Koch,et al.  Organic electronic devices and their functional interfaces. , 2007, Chemphyschem : a European journal of chemical physics and physical chemistry.

[17]  Chun-Sing Lee,et al.  Efficient organic photovoltaic devices using a combination of exciton blocking layer and anodic buffer layer , 2006 .

[18]  James Kirkpatrick,et al.  Factors limiting the efficiency of molecular photovoltaic devices , 2004 .

[19]  Jan Kalinowski,et al.  Mixing of Excimer and Exciplex Emission: A New Way to Improve White Light Emitting Organic Electrophosphorescent Diodes , 2007 .

[20]  Jingui Qin,et al.  Multifunctional Triphenylamine/Oxadiazole Hybrid as Host and Exciton‐Blocking Material: High Efficiency Green Phosphorescent OLEDs Using Easily Available and Common Materials , 2010 .

[21]  A J Heeger,et al.  Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols. , 2007, Nature materials.

[22]  A. Heeger,et al.  Improved high-efficiency organic solar cells via incorporation of a conjugated polyelectrolyte interlayer. , 2011, Journal of the American Chemical Society.

[23]  Srinivas Sista,et al.  Tandem polymer photovoltaic cells—current status, challenges and future outlook , 2011 .

[24]  Junsheng Yu,et al.  High performance polymer light-emitting diodes doped with a novel phosphorescent iridium complex , 2009 .

[25]  K. Leo,et al.  Imbalanced mobilities causing S-shaped IV curves in planar heterojunction organic solar cells , 2011 .