摘要
本论文的工作主要研究聚合物太阳电池的界面调控问题。在分析聚合物太阳电池电极修饰层的作用以及回顾聚合物太阳电池电极修饰材料研究进展的基础上,系统研究了不同的阴、阳极修饰层(共轭聚电解质,氧化钼MoO_3)对聚合物太阳电池性能尤其是开路电压的影响;系统分析了开路电压的影响因素,并提出了提高聚合物太阳电池开路电压的新的方法;在此基础上,将阴、阳极修饰层组成的中间电极成功地应用于叠层聚合物太阳电池,为聚合物太阳电池性能的进一步提高打下了坚实基础。
共轭聚电解质被广泛地应用于聚合物电致发光器件(polymer light emitting diodes, PLED),但其在聚合物太阳电池中的应用比较少见。我们将共轭聚电解质作为阴极修饰层,成功地应用于聚合物太阳电池。发现通过选择带合适的极性基团的共轭聚电解质,优化其厚度,能够有效地提高聚合物太阳电池的短路电流及填充因子,改善其性能。更重要的是,某些材料体系器件的开路电压(例如PFO-DBT35)由于共轭聚电解质层的引入得到了大幅提升。在分析共轭聚电解质层在聚合物太阳电池器件中的作用,并详细分析各组器件暗电流差别的基础上,我们用经典p-n结的肖克莱方程阐述了开路电压提高的原因。
MoO_3是一个良好的阳极修饰层。文献中很多关于它对聚合物太阳电池短路电流、填充因子及整体性能的影响,却很少见到关于它对提高聚合物太阳电池器件开路电压的研究。MoO_3应用于P3HT、MEH-PPV、PFO-DBT35器件,发现对于具有更低HOMO能级的PFOD-BT35器件,其开路电压大幅提升。在综合分析其他一些实验结果的基础上,我们认为PFOD-BT35器件开路电压的提升并不是来自于阳极更好的欧姆接触,而可能是因为MoO_3的引入使得PFOD-BT35器件活性层中给体与受体在垂直方向上的产生了梯度分布,从而阴极处的PCBM有效的保护了活性层,防止了Al对PFOD-BT35的破坏而引起的能带弯曲。
在上述阴、阳极修饰工作的基础上,提出了PFN/Al/MoO_3(PFN为一种共轭聚电解质)的三层结构中间电极,应用于叠层聚合物太阳电池。该中间电极加工相对简单,稳定性好,且具有良好的光、电学性能。通过选用窄带隙材料PBDT-DTNT器件作为上层子电池,得到了高达1.65V的开路电压,并成功使得叠层器件的效率超过了3%,填充因子超过了50%。我们认为,若选择更加合适的上层子电池给体材料,叠层聚合物太阳电池的效率将会有更大幅度的提升。
The thesis focuses on interface engineering between active layer and electrodes for polymer solar cells (PSCs). After a brief review of the interlayer materials and their functions, we carried a systematic study on the effects of interlayers from such as conjugated polyelectrolytes and MoO_3 on the performances of PSCs, especially on the open circuit voltage (Voc). We successfully increased the Voc via electrode modification and analyzed the origin of its enhancement. In addition, we proposed a novel intermediate layer for polymer tandem solar cells with the structure of PFN/Al/MoO_3, which provides an opportunity for further improvement of the performance of PSCs.
Conjugated polyelectrolytes have been widely used as electron injection layer in PLEDs, but not very well investigated in PSCs so far. It was first time reported by our group that polyelectrolyte as cathode interlayer could significantly enhance Voc in PSCs. In this study we found out that not only Voc, both the short circuit current (Isc) and fill factor (FF) of PSCs can be also enhanced with proper polyelectrolytes of right thickness for certain donor polymers such as PFO-DBT35 when proper polyelectrolytes were used as cathode interlayer. After a careful analysis about the function of polyelectrolytes in the device and the dark I-V curves of devices, we interpreted the origin of the Voc enhancement can be explained based on Shockley’s equation analysis.
MoO_3 is an excellent anode interlayer. There are plenty of reports about using MoO_3 to increase the efficiency of PSCs, but much less investigated its effect on Voc enhancement. We replaced PEDOT:PSS with MoO_3 in devices of P3HT, MEH-PPV and PFO-DBT35. We found an increase in Voc of PFO-DBT35 (with a deeper HOMO) devices. With all the data considered, we attributed the increase in Voc of PFO-DBT35 devices not to a better ohmic contact between anode and active layer, but to a vertical phase separation caused by MoO_3.
Finally, we proposed a new intermediate layer for polymer tandem solar cells with the structure of PFN/Al/MoO_3. This novel intermediate layer for tandem cell is chemically stable in air and can be easily processed. The intermediate layer shows good optical and electrical properties. With devices of a novel low band-gap conjugated polymer PBDT-DTNT as top cells, we gained a Voc as high as 1.65V, ECE exceeding 3%, and FF exceeding 50%. We believe that the performance of polymer tandem solar cells with PFN/Al/MoO_3 as intermediate layer will be enormously improved once a more suitable top cell is introduced.
引文
[1]. Shirakawa H., MacDiarmid A.G., Heeger A.J., et al. Synthesis of electrically conducting organic polymers:halogen derivatives of polyacetylene. Journal of the Chemical Society,Chemical Communication,1977,578-580
[2]. Chen H.Y., Yang Y., Li G., et al. Polymer solar cells with enhanced open-circuit voltage and efficiency. Nat. Photonics,2009,3:649
[3]. Park S.H., Leclerc M., Heeger A.J., et al. Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nat. Photonics,2009,3:297
[4]. Liang Y.Y., Li G., Y L.P., et al. For the Bright Future—Bulk Heterojunction Polymer Solar Cells with Power Conversion Efficiency of 7.4%. Adv. Mater., 2010,22,:E135–E138
[5]. Solarmer homepage, http://www.solarmer.com
[6]. Chu T.Y., Lu J.P., Tao Y., et al. Bulk Heterojunction Solar Cells Using Thieno[3,4-c]pyrrole-4,6-dioneand Dithieno[3,2-b:20,30-d]silole Copolymer with a Power Conversion Efficiency of 7.3%. J. Am. Chem. Soc.,2011,133:4250–4253
[7]. Son H.J, Wang W., Yu L.P., et al. Synthesis of Fluorinated Polythienothiophene-co-benzodithiophenes and Effect of Fluorination on the Photovoltaic Properties. J. Am. Chem. Soc.,2011, 133:1885–1894
[8]. Hoppe H., Sariciftci N.S. Morphology of polymer/fullerene bulk heterojunction solar cells. J.Mater.Chem.,2006,16:45-61
[9]. Thompson B.C., Frechet J.M.J., Polymer–Fullerene Composite Solar Cells. Angew. Chem. Int. Ed.,2008,47:58–77
[10]. Bulliard X., Soo G.I., Cho K., et al., Enhanced Performance in Polymer Solar Cells by Surface Energy Control. Adv. Funct. Mater.,2010,20:4381–4387
[11]. Yip H.L., Hau S.K., Jen A.K.Y., et al. Polymer Solar Cells That Use Self-Assembled-Monolayer-Modified ZnO/Metals as Cathode. Adv. Mater., 2008, 20: 2376–2382
[12]. Tengstedt C., Unge M., Fahlman M., et al. Coulomb interactions in rubidium-doped tetracyanoethylene: A model system for organometallic magnets. Phys. Rev. B 2004,69:165208
[13]. Johansson M., Osada T., Bredas J.L., et al. Electronic structure of tris(8-hydroxyquinoline) aluminum thin films in the pristine and reduced states. J. Chem. Phys. 1999,111:2157
[14]. Braun S., Salaneck W.R., Fahlman M. Energy-Level Alignment at Organic/Metal and Organic/Organic Interfaces. Adv. Mater. 2009, 21, 1450–1472
[15]. Crispin A., Crispin X., Salaneck W.R., et al. Transition between energy level alignment regimes at a low band gap polymer-electrode interfaces. APPLIED PHYSICS LETTERS,2006,89, 213503
[16]. Mihailetchi V.D., Blom P.W.M., Hummelen J.C., et al. Cathode dependence of the open-circuit voltage of polymer:fullerenebulk heterojunction solar cells. J. Appl. Lett.,2003,94: 6849
[17]. Scharber M.C., Mühlbacher D., Brabec C.J., et al. Design Rules for Donors in Bulk-Heterojunction Solar Cells—Towards 10% Energy-Conversion Efficiency. Adv. Mater.,2006,18:789–794
[18]. Smith J.J. B., Goris L., Nelson J., et al. Formation of a Ground-State Charge-Transfer Complex in Polyfluorene/[6,6]-Phenyl-C61 Butyric Acid Methyl Ester (PCBM)Blend Films and Its Role in the Function of Polymer/PCBM Solar Cells. Adv.Funct.Mater.,2007,17:451-457
[19]. Loi M.A., Toffanin S., Scharber M., et al. Charge Transfer Excitons in Bulk Heterojunctions of a Polyfluorene Copolymer and a Fullerene Derivative. Adv. Funct. Mater.,2007,17:2111-2116
[20]. Vandewal K., Gadisa A., Manca J.V., et al. The Relation Between Open-Circuit Voltage and the Onset of Photocurrent Generation by Charge-Transfer Absorption in Polymer : Fullerene Bulk Heterojunction Solar Cells. Adv. Funct. Mater., 2008,18:2064
[21]. Kumar A., Sista S., Yang Y. Dipole induced anomalous S-shape I-V curves in polymer solar cells. J.Appl.Phys.,2009,105: 094512
[22]. Lee K., Kim J.Y., Heeger A.J., et al. Air-Stable Polymer Electronic Devices. Adv. Mater.,2007,19: 2445
[23]. Walzer K., Maennig B., Leo K., et al. Highly Efficient Organic Devices Based onElectrically Doped Transport Layers. Chem. Rev., 2007,107, 1233
[24]. Ma W.L., Iyer P.K., Gong X., et al. Water/Methanol-Soluble Conjugated Conjugated Copolymer as an Electron-Transport Layer in Polymer Light-Emitting Diodes. Adv. Mater. 2005, 17: 274
[25]. Yang R.Q., Wu H.B., Cao Y., et al. Control of Cationic Conjugated Polymer Performance in Light Emitting Diodes by Choice of Counterion. J. Am. Chem. Soc. 2006, 128: 14422-14423
[26]. Waldauf C., Morana M., Brabec C.J.,et al. Highly efficient inverted organic photovoltaics using solution based titanium oxide as electron selective contact. Appl.Phys.Lett.,2006,89:233517
[27]. Hayakawa A., Yoshikawa O., Yoshikawa S.,et al. High performance polythiophene/fullerene bulk-heterojunction solar cell with a TiOx hole blocking layer. Appl.Phys.Lett., 2007, 90, 163517
[28]. Steim R., Kogler F.R., Brabec C.B. Interface materials for organic solarcells. J.Mater.Chem.,2010,20:2499–2512
[29]. Kim J.Y., Kim S. H., Heeger A. J., et al. New architecture for high-efficiency polymer photovoltaic cells using solution-based titanium oxide as an optical spacer. Advanced Materials,2006,18: 572-576
[30]. Zhang C.F., Tong S.W., Zhu C.X., et al. Efficient multilayer organic solar cells using the optical interference peak. Appl.Phys.Lett.,2008,93:043307
[31]. Zhang F.L., Svensson M., Andersson M.R., et al. Influence of buffer layers on the performance of polymer solar cells. Appl.Phys.Lett.,2004,84:3906-3908
[32]. Brabec C.J., Cravino A., Hummelen J.C., Origin of the Open Circuit Voltage of Plastic Solar Cells. Adv. Funct. Mater.,2001,11: 374
[33]. Gupta D., Bag M., Narayan K. S. Correlating reduced fill factor in polymer solar cells to contact effects. Appl. Phys. Lett., 2008, 92:093301
[34]. Reese M.O., White M.S., Shaheen S.E. Optimal negative electrodes for poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester bulk heterojunction photovoltaic devices. Appl. Phys. Lett.,2008, 92,:053307
[35]. Shaheen S.E., Brabec C.J., Hummelen J.C.,et al. 2.5% efficient organic plastic solarcells. Appl. Phys. Lett.,2001,78:841
[36]. Brabec C.J., Shaheen S.E., Denk P., et al. Effect of LiF/metal electrodes on the performance of plastic solar cells. Appl. Phys. Lett.,2002,80:1288
[37]. Limketkai B.N., Baldo M.A. Charge injection into cathode-doped amorphous organic semiconductors. Phys. Rev. B: Condens. Matter Mater. Phys., 2005,71:085207
[38]. Jabbour G.E., Kippelen B., Peyghambarian N., et al. Aluminum based cathode structure for enhanced electron injection in electroluminescent organic devices. Appl. Phys. Lett.,1998,73: 1185
[39]. Lee J., Park Y., Zyung T.,et al. Tris-(8-hydroxyquinoline)aluminum-based organic light-emitting devices with Al/CaF2 cathode: Performance enhancement and interface electronic structures. Appl. Phys. Lett., 2002,80:3123
[40]. Lee J., Park Y., Do L.M.,et al. High efficiency organic light-emitting devices with Al/NaF cathode. Appl.Phys. Lett.,2003, 82:173
[41]. Huang J., Xu Z., Yang Y., Low-Work-Function Surface Formed by Solution-Processed and Thermally Deposited Nanoscale Layers of Cesium Carbonate. Adv. Funct. Mater., 2007, 17:1966
[42]. Li G., Chu C.W., Yang Y.,et al. Efficient inverted polymer solar cells. Appl. Phys.Lett.,2006, 88:253503
[43]. Chen F.C., Wu J.L.,Chen W.C., et al. Cesium carbonate as a functional interlayer for polymer photovoltaic devices. J. Appl. Phys.,2008,103:103721
[44]. Kim J.Y., Kim S.H., Heeger A.J., et al. New Architecture for High-Efficiency Polymer Photovoltaic Cells. Adv. Mater.,2006,18:572
[45]. Park S.H., Roy A., Heeger A.J., et al. Bulk heterojunction solar cells with internal quantum efficiency approaching 100%. Nat. Photonics,2009, 3, 297
[46]. Hayakawa A., Yoshikawa O., Yoshikawa S.,et al High performance polythiophene fullerene bulk heterojunction solar cell with a TiOx hole blocking layer. Appl. Phys. Lett.,2007,90:163517
[47]. Roest A.L., Kelly J.J., Meulenkamp E.A.,et al. Staircase in the Electron Mobility of a ZnO Quantum Dot Assembly due to Shell Filling. Phys. Rev. Lett.,2002,89:036801
[48]. Gilot J., Barbu I., Janssen R.A.J.,et al. The use of ZnO as optical spacer in polymersolar cells: Theoretical and experimental study. Appl. Phys.Lett.,2007,91:113520
[49]. Andersson B.V., Huang D.M., Inganas O.,et al. An optical spacer is no panacea for light collection in organic solar cells. Appl.Phys. Lett.,2009,94:043302
[50]. Sista S., Park M.H., Yang Y., et al. Highly Efficient Tandem Polymer Photovoltaic Cells. Adv. Mater.,2010,22: 380
[51]. Chou C.H. , Kwan W.L., Yang Y.,et al. Metal-Oxide Interconnection Layer for Polymer Tandem Solar Cells with an Inverted Architecture. Adv.Mater.,2011, 23:1282–1286
[52]. Kim J.Y., Lee K.H., Heeger A.J, et al. Efficient Tandem Polymer Solar Cells Fabricated by All-Solution Process. Science,2007,317: 222
[53]. Kim J.H., Sung Y.H., Lee H.H., et al. Thin pentacene interlayer for polymer bulk-heterojunction solar cell. Appl. Phys.Lett.,2008,93:143305
[54]. Gommans H.,Verreet B., Genoe J., et al. On the Role of Bathocuproine in Organic Photovoltaic Cells. Adv.Funct.Mater.,2008,18:3686–3691
[55]. Chang C.C., Lin C.F., Chen K.H., et al. Effects of cathode buffer layers on the efficiency of bulk-heterojunction solar cells. Appl. Phys.Lett.,2010,96:263506
[56]. Yu H.Z., Peng J.B. Performance and lifetime improvement of polymer/fullerene blend photovoltaic cells with a C60 interlayer. Organic Electronics, 2008,9:1022–1025
[57]. Khodabakhsh S., Nelson J., Jones T.S. Use self-assambling dipole molecules to improve hole-injection in polymer materials. Adv.Funct. Mater.,2004,14:1205–1210
[58]. Khodabakhsh S., Sanderson B.M., Jones T.S.,et al Using self-assembling dipole molecules to improve charge collection in molecular solar cells,Adv.Funct. Mater.,2006,16:95–100
[59]. Kim J.S., Park J.H., Cho K., et al. Control of the electrode work function and active layer morphology via surface modification of indium tin oxide for high efficiency organic photovoltaics. Appl.Phys. Lett.,2007, 91:112111
[60]. Yip H.L., Hau S.K., Jen A.K.Y.,et al. High performance ambient processed inverted polymer solar cells through interfacial modification with a fullerene self-assembled monolayer. Appl.Phys. Lett.,2008, 92:193313
[61]. Yip H.L., Hau S.K., Jen A.K.Y., et al. Polymer Solar Cells That UseSelf-Assembled-Monolayer-Modified ZnO/Metals as Cathode. Adv. Mater.,2008,20:2376–2382
[62]. Zhang F.L., Ceder M., Inganas O., Enhancing the photovoltage of polymer solar cells by using a modified cathode. Adv. Mater.,2007,19:1835
[63]. Luo J., Wu H.B., Cao Y., et al. Enhanced open-circuit voltage in polymer solar cells. Appl.Phys. Lett.,2009,95: 043301
[64]. Oh S.H., Na S.I., Kim D.Y., et al. Water-Soluble Polyfluorenes as an Interfacial LayerLeading to Cathode-Independent High Performance of Organic Solar Cells. Adv. Funct. Mater. 2010,20:1977–1983
[65]. Zhang F.L., Johansson M, Inganas O., et al. Polymer Photovoltaic Cells with Conducting Polymer Anodes. Adv. Mater.,2002,14:662
[66]. Zhang F.L., Inganas O., Andersson M.R., et al. Influence of buffer layers on the performance of polymer solar cells. Appl.Phys. Lett.,2004,84: 3096
[67]. Jong M.P., IJzendoorn L.J., Voigt M.J.A. Stability of the interface between indium-tin-oxide and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) in polymer light-emitting diodes. Appl.Phys. Lett.,2000,77: 2255
[68]. Kim Y.H., Lee S.H., Han S.H., et al. Performance and stability of electroluminescent device with self-assembled layers of poly (3, 4-ethylenedioxythiophene)-poly (styrenesulfonate) and polyelectrolytes. Thin Solid Films,2006,510:305
[69]. Wong K.W., Yip H.L., Chang C.C., et al. Blocking reactions between indium-tin oxide and poly (3,4-ethylene dioxythiophene):poly(styrene sulphonate) with a self-assembly monolayer. Appl. Phys. Lett.,2002,80:2788
[70]. Shrotriya V., Li G., Yang Y., et al Transition metal oxides as the buffer layer for polymer photovoltaic cells. Appl. Phys. Lett.,2006,88:073508
[71]. Kinoshita Y., Takenaka R., Murat H. Independent control of open-circuit voltage of organic solar cells by changing film thickness of MoO3 buffer layer. Appl. Phys. Lett.,2008,92:243309
[72]. Zhao D.W., Sun X.W., Kwong D.L., et al. Efficient tandem organic solar cells with an Al/MoO3 intermediate layer. Appl. Phys. Lett.,2008,93:083305
[73]. Irwin M.D., Buchholz D.B.,Marks T.J., et al. p-Type semiconducting nickel oxide asan efficiency-enhancing anode interfacial layer in polymer bulk-heterojunction solar cells. Proc. Natl. Acad. Sci. U. S. A.,2008,105:2783
[74]. Park S.Y., Kim H.R., Kang J.W., et al. Organic solar cells employing magnetron s puttered p-type nickel oxide thin film astheanodebufferlayer. Solar EnergyMaterials&SolarCells,2010,9:42332–2336
[75]. Gustafsson G., Cao Y., Heeger A.J., et al. Flexible light-emitting diodes made from soluble conducting polymers,Nature,1992,357:477
[76]. Yang Y., Heeger A.J. A new architecture for polymer transistors. Appl. Phys. Lett.,1994,64:1245.)
[77]. Li C.Y., Wen T.C., Hou S.S., et al. A facile synthesis of sulfonated poly (diphenylamine) and the application as a novel hole injection layer in polymer light emitting diodes. Polymer,2008,49:957
[78]. Li C.Y., Wen T.C., Hsu Y.J., et al. An inverted polymer photovoltaic cell with increased air stability obtained by employing novel hole/electron collecting layers. J. Mater. Chem.,2009,19:1643
[79]. Jang J., Ha J., Kim K. Organic light-emitting diode with polyaniline-poly (styrene sulfonate) as a hole injection layer. Thin Solid Films,2008,516:3152
[80]. Li S.S., Tu K.H., Chhowalla M., et al. Solution-Processable Graphene Oxide as an Efficient Hole Transport Layer in Polymer Solar Cells. ACSNANO,2010,4:3169–3174
[81]. Ko C.J., Lin Y.K., Chu C.W., et al. Modified buffer layers for polymer photovoltaic devices, Appl.Phys.Lett.,2007,90:063509
[82].邓先宇,俞钢,曹镛.聚合物光诱导电荷转移光电池的研究进展.固体电子学研究与进展,2002,22:249-254
[83]. Knupfer M. Exciton binding energies in organic semiconductors. Applied Physics A: Materials Science & Processing,2003,77:623-626
[84]. Chandross M., Mazumdar S., Miller T.M., et al. Excitons in poly(para-phenylenevinylene). Physical Review B,1994,50:14702-5
[85]. Halls J.J.M., Pichler K., Holmes A.B., et al. Exciton diffusion and dissociation in a poly (p-phenylenevinylene)/C60 heterojunction photovoltaic cell. Appl.Phys.Lett.,1996,68:3120-3122
[86]. Haugeneder A., Neges M., Müllen K., et al. Exciton diffusion and dissociation in conjugated polymer/fullerene blends and heterostructures. Physical Review B,1999,59,:15346-15351
[87]. Sariciftci N.S., Heeger A.J., Wudl F. Photoinduced electron transfer from a conducting polymer to buckminsterfullerene. Science,1992,258:1474
[88]. Blom P.W.M., Mihailetchi V.D., Markov D.E., et al. Device Physics of Polymer:Fullerene Bulk Heterojunction Solar Cells
[89]. Petritsch D.I.K. Organic solar cell architectures. PhD thesis of Technisch- Naturwissenschaftliche Fakult?t der Technischen Universit?t Graz (Austria),2000
[90]. Riedel I., Dyakonov V., Hummelen J.C., et al. Effect of Temperature and Illumination on the Electrical Characteristics of Polymer-Fullerene Bulk-Heterojunction Solar Cells. Adv. Funct. Mater.,2004,14,NO.1,January
[91]. Katz E.A., Faiman D., Sariciftci N.S., et al. Temperature dependence for the photovoltaic device parameters of polymer-fullerene solar cells under operating conditions. JOURNAL OF APPLIED PHYSICS,2001,90,5343
[92]. Brabec C.J., Sariciftci N.S., Hummelen J.C. Plastic solar cells. Adv. Funct. Mater.,2001,11:15-26
[93]. Frohne H., Shaheen S.E., Brabec C.J. Influence of the anodic work function on the performance of organic solar cells. Chemphyschem: a European journal of chemical physics and physical chemistry,2002,3:795
[94]. Ma W.L., Yang C.Y., Heeger A.J., et al. Thermally Stable, Efficient Polymer Solar Cells with Nanoscale Control of the Interpenetrating Network Morphology. Adv. Funct. Mater.,2005,15:1617-1622
[95]. Chirvase D., Chiguvare Z., Knipper A. Temperature dependent characteristics of poly(3- hexylthiophene)-fullerene based heterojunction organic solar cells. Journal of Applied Physics,2003,93:3376-3383
[96]. Cao Y., Yu G., Heeger A.J., et al. Polymer light-emitting diodes with polyethylene dioxythiophene-polystyrene sulfonate as the transparent anode. Synthetic Metals,1997,87:171-174
[97].王藜博士毕业论文提高聚合物异质结太阳电池性能研究:CdS纳米晶及新型窄带隙共聚物的应用,[D]华南理工大学2008
[98]. (NREL),http://www.udel.edu/igert/pvcdrom/APPEND/AM1_5.HTML
[99]. Hirose Y., Kahn A., Soukiassian P., et al. Chemistry, diffusion, and electronic properties of a metal/organic semiconductor contact: In/perylenetetracarboxylic dianhydrid. Appl. Phys.Lett.,1996,68:217
[100]. Fou A. C., Onitsuka O., Hsieh B.R., et al. Fabrication and properties of light-emitting diodes based on self-assembled multilayers of poly(phenylene vinylene). Journal of Applied Physics,1996,79:7501-7509
[101]. Wu H.B., Huang F., Cao Y., et al. Efficient electron injection from a bilayer cathode consisting of aluminum and alcohol-/water-soluble conjugated polymers. Adv. Mater.,2004,16:1826
[102]. Huang F., Wu H.B., Cao Y., et al. Novel electroluminescent conjugated polyelectrolytes based on polyfluorene. Chem. Mater.,2004,16:708-716
[103]. Huang F., Hou L.T., Cao Y., et al. High-efficiency, environment-friendly electroluminescent polymers with stable high work function metal as a cathode: Green- and yellow-emitting conjugated polyfluorene polyelectrolytes and their neutral precursors. J. Am. Chem. Soc.,2004,126: 9845-9853
[104]. Zeng W.J., Wu H.B., Cao Y., et al. Polymer light-emitting diodes with cathodes printed from conducting Ag paste. Adv. Mater.,2007,19:810
[105]. Yang R.Q., Garcia A., Nguyen T.Q.,et al. Control of Interchain Contacts, Solid-State Fluorescence Quantum Yield, and Charge Transport of Cationic Conjugated Polyelectrolytes by Choice of Anion. J. AM. CHEM. SOC.,2006,128:16532-16539
[106]. Reese M.O., White M.S., Shaheen S.E., et al. Optimal negative electrodes for poly(3-hexylthiophene): [6,6]-phenyl C61-butyric acid methyl ester bulk heterojunction photovoltaic devices, Appl. Phys. Lett.,2008,92:053307
[107]. Wu H.B., Huang F., Cao Y., et al. High-efficiency electron injection cathode of Au for polymer light-emitting devices. Organic Electronics,2005,6:118–128
[108]. Maher Al-Ibrahim and Oliver Ambacher ,Effects of solvent and annealing on the improved performance of solar cells based on poly
[109]. Johnev B., Vogel M., Weidinger A., et al. Monolayer passivation of the transparent electrode in organic solar cells. Thin Solid Films,2005,488:270
[110]. Takahashi K., Suzaka S., Murata K., et al. Efficiency increase by insertion of electrodeposited CuSCN into ITO/organic solid interface in bulk hetero-junction solar cells consisting of polythiopheneand fullerene. Chem. Lett.,2007,36:762–763
[111]. White M.S., Olson D.C., Ginley D.S., et al. Inverted bulkheterojunction organic photovoltaic device using a solution-derived ZnO underlayer. Appl. Phys. Lett.,2006,89:143517
[112]. You H., Dai Y.F., Ma D.G., et al. JOURNAL OF APPLIED PHYSICS,2007,101:026105
[113]. Bolink H.J., Coronado E., Sessolo M., et alEfficient Polymer Light-Emitting Diode Using Air-Stable Metal Oxides as Electrodes
[114]. Morii K., Ishida M., Gr?tzel M., et al. Encapsulation-free hybrid organic-inorganic light-emitting diodes. APPLIED PHYSICS LETTERS,2006,89:183510
[115]. Tao C., Ruan S.P., Chen W.Y., et al. Performance improvement of inverted polymer solar cells with different top electrodes by introducing a MoO3 buffer layer. APPLIED PHYSICS LETTERS,2008,93:193307
[116]. Cattin L., Dahou F., Bernède J.C., et al. MoO3 surface passivation of the transparent anode in organic solar cellsusing ultrathin films. Appl. Phys. Lett.,2009,105:034507
[117]. Jens Meyer J., Khalandovsky R., Kahn A., et al.MoO3 Films Spin-Coated from a Nanoparticle Suspension for Effi cient Hole-Injection in Organic Electronics. Adv. Mater. 2011, 23:70–73
[118]. Hong Z.R., Liang C.J., Zeng X.T., et al. Characterization of organic photovoltaic devices with indium-tin-oxide anode treated by plasma in various gases. J. Appl. Phys. 2006,100:093711
[119]. Helander M.G., Wang Z.B., Lub Z.H., et al. The effect of UV ozone treatment on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). Appl. Phys. Lett.,2009,95:173302)
[120]. Lee H.K, Kim J.K., Park O.O. Effects of UV light-irradiated buffer layer on the performance of polymer solar cells. Organic Electron,2009,10:1641
[121]. Xu Z., Chen L.M.,Yang Y., et al. Vertical Phase Separation in Poly(3-hexylthiophene):Fullerene Derivative Blends and its Advantage for Inverted Structure Solar Cells. Adv. Funct. Mater. 2009, 19:1227–1234
[122]. Svanstrom C.M.B., Rysz J., Moons E., et al. Device Performance of APFO-3/PCBM Solar Cells with Controlled Morphology. Adv. Mater.,2009, 21:4398-4403
[123]. Snaith H.J., Greenham N.C., Friend R.H. The origin of collected charge and open circuit voltage of blended polyfluorene photovoltaic cells. Adv. Mater.,2004,16:1640
[124]. Bjorstrom C.M., Bernasik A., Moons E., et al. Multilayer formation in spin-coated thin films oflow-bandgap polyfluorene:PCBM blends. J. Phys.: Condens. Matter,2005,17:L529–L534
[125]. Svanstrom C.M.B., Rysz J., Moons E., et al. Device Performance of APFO-3/PCBM Solar Cells with Controlled Morphology. Adv. Mater.,2009, 21:4398-4403
[126]. Hadipour A., Boer B., Blom P.W.M., et al. Solution-Processed Organic Tandem Solar Cells. Adv. Funct. Mater.,2006,16:1897–1903
[127]. Hadipour A., Boer B., Blom P.W.M. Device operation of organic tandem solar cells. Organic Electronics,2008,9:617–624
[128]. Ameri T., Dennler G., Brabec C.J., et al. Organic tandem solar cells: A review. Energy Environ. Sci., 2009, 2, 347–363
[129]. Zhao D.W., Sun X.W., Kwong D.L., et al. Efficient tandem organic solar cells with an Al/MoO3 intermediate layer. Appl. Phys. Lett.,2008,93:083305
[130]. Hadipour A., Boer B., Blom P.W.M., et al. Solution-Processed Organic Tandem Solar Cells. Adv. Funct. Mater.,2006,16:1897–1903
[131]. Shrotriya V., Wu E.H.E., Yang Y., et al. Efficient light harvesting in multiple-device stacked structure for polymer solar cells. Appl. Phys. Lett.,2006,88:064104
[132]. Zhao D.W., Sun X.W., Kwong D.L., et al. Efficient tandem organic solar cells with an Al/MoO3 intermediate layer. Appl. Phys. Lett.,2008,93:083305
[133]. Gilot J., Wienk M.M., Janssen R.A.J. Double and triple junction polymer solar cells processed from solution, Appl. Phys. Lett.,2007,90,143512
[134]. Gilot J., Wienk M.M., Janssen R.A.J. Optimizing Polymer Tandem Solar Cells, Adv. Mater.,2010,22: E67–E71
[135]. Boland P., Lee K.J., Gon N.K., et al. Design of organic tandem solar cells using low-and high-bandgap polymer:fullerene composites, Solar Energy Materials&Solar Cells,2010,94:2170–2175
[136]. Moet D.J.D., Bruyn P., Blom P.W.M. High work function transparent middle electrode for organic tandem solar cells,Appl.Phys. Lett.,2010,96:153504
[137]. Gilot J., Wienk M.M., Janssen R.A.J. Measuring the External Quantum Efficiency of Two-Terminal Polymer Tandem Solar Cells, Adv. Funct. Mater.,2010,20:39
[138]. Wang M., Hu X.W., Cao Y., et al. A Donor-Acceptor Conjugated Polymer Based on Naphtho[1,2-c:5,6-c]bis[1,2,5]thiadiazole for High Performance Polymer Solar cells. J. Am. Chem. Soc.,2011,XXX
