[雙語翻譯]--外文翻譯--低價(jià)帶半導(dǎo)體雙富勒烯異質(zhì)結(jié)中區(qū)分富勒烯相分離（英文）

1、FULL PAPER© 2014 WILEY-VCH Verlag GmbH while replacing PCBM with ICBA in these devices results in a PCE of 2.7%. [ 10 ] This poor performance is associated with either poor morphology or hindered charge tran

2、sport in the active layer. [ 8–13 ] However, these reported values are only based on the as-cast low band-gap polymer (LBP):ICBA device, where there is very little control of the morphology. [ 8–13 ] As J sc

3、and PCE strongly depend on the morphology, the high V oc might translate into dramatic improvements in power conversion efficiencies if the morphology of the LBP:ICBA mixture can be rationally controlled. Unfortunat

4、ely, little work has been done to optimize the morphology of these systems after film deposition. Distinguishing the Importance of Fullerene Phase Separation from Polymer Ordering in the Performance of Low Band Gap Po

5、lymer:Bis-Fullerene Heterojunctions Huipeng Chen , Yu-Che Hsiao , Jihua Chen , Bin Hu , and Mark Dadmun * One way to improve power conversion efficiency (PCE) of polymer based bulk-heterojunction

6、(BHJ) photovoltaic cells is to increase the open cir-cuit voltage ( V oc ). Replacing PCBM with bis-adduct fullerenes significantly improves V oc and the PCE in devices based on the conjugated polymer poly(3-hexyl

7、thiophene) (P3HT). However, for the most promising low band-gap polymer (LBP) system, replacing PCBM with ICBA results in poor short-circuit current ( J sc ) and PCE although V oc is significantly improved. The opt

8、imiza-tion of the morphology of as-cast LBP/bis-fullerene BHJ photovoltaics is attempted by adding a co-solvent to the polymer/fullerene solution prior to film deposition. Varying the solubility of polymer and fullerene

9、in the co-sol-vent, bulk heterojunctions are fabricated with no change of polymer ordering, but with changes in fullerene phase separation. The morphologies of the as-cast samples are characterized by small angle neutron

10、 scattering and neu-tron reflectometry. A homogenous dispersion of ICBA in LBP is found in the samples where the co-solvent is selective to the polymer, giving poor device performance. Aggregates of ICBA are formed in sa

11、mples where the co-solvent is selective to ICBA. The resultant morphology improves PCE by up to 246%. A quantitative analysis of the neutron data shows that the interfacial area between ICBA aggregates and its surroundin

12、g matrix is improved, facilitating charge transport and improving the PCE. 1. Introduction Organic photovoltaic (OPV) devices based on the bulk hetero- junction (BHJ) concept of blends of conjugated polymers and fulle

13、renes have attracted significant interest for sustainable solar energy conversion due to their low-cost, light-weight, flex- ible and ease of processing. [ 1–5 ] The power conversion efficiency (PCE) of these device

14、s has increased rapidly in recent years, which has been primarily due to the development of novel donor DOI: 10.1002/adfm.201401419Dr. H. P. Chen, Prof. M. Dadmun Department of Chemistry University of Tennessee Knoxvill

15、e , TN 37996 , USA E-mail: Dad@utk.edu Dr. Y.-C. Hsiao, Prof. B. Hu Department of Materials Science and Engineering University of Tennessee Knoxville , TN 37996 , USA Dr. J. H. Chen Center for Nanophas

16、e Materials Sciences Oak Ridge National Lab Oak Ridge , TN 37831 , USA Prof. M. Dadmun Chemical Sciences Division Oak Ridge National Lab Oak Ridge , TN 37831 , USA Adv. Funct. Mater. 2014, 24, 7284–7290ww

17、w.afm-journal.de www.MaterialsViews.comFULL PAPER7286 wileyonlinelibrary.com © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheimthat is cast from 100% ODCB (AC), so the resultant depth pro- files are normalized to

18、 its thickness and are shown in Figure 3 . The thicknesses of the samples are 400 Å, 390 Å, and 380 Å for the AC, 4% BB, and 4% CP samples, respectively. In this figure, z = 0 corresponds to the air

19、-film interface while z = 1 corre- sponds to the film-silicon interface. Inspection of this depth profile shows that a plateau region with constant ICBA concen- tration exists at z ≈ 0.4-0.7 in the sample that is ca

20、st from 100% ODCB (AC). This portion of the film is not impacted by the air interface or silicon surface. Selective segregation of ICBA to the silicon surfaces is observed in this AC thin film. Enhanced segregation o

21、f ICBA to the silicon surface and a depletion of ICBA at the air surface are observed when 4% BB, in which PCPDTBT is selective soluble, is added to ODCB. An oppo- site modification is observed when 4% CP, in which ICB

22、A is selective soluble, is added to ODCB. In this sample (4% CP), a depletion of ICBA at the silicon surface and enhanced segrega- tion of ICBA to the air surface are observed. Reflectometry, however, only provides inf

23、ormation on the vertical morphology of these samples, but does not provide information on the in-plane morphology that is formed when a second solvent is added to the depositing solution. Thus, small angle neutron sca

24、ttering (SANS) was employed to pro- vide information on the alteration of the in-plane morphologies of the samples with the addition of the second solvent to the depositing solution. The SANS curves of all of the sampl

25、es are presented in Figure 4 . The scattering intensity in these curves is proportional to the square of the difference of the scattering length density of the scattering object and its surroundings. Thus, the s

26、cattering is very weak if there is no or very little phase separation. The scattering of the sample that is cast from 100% ODCB (AC) sample is very weak, which is consistent with previous reports that the as-cast PCPD

27、TBT/PCBM films from 100% ODCB consist of a fairly homogeneous distribution of the fullerene and polymer in this film. [ 14 ] An even weaker scattering is observed when the solvent contains 4% BB, which indicates a

28、 better dispersion of the ICBA and PCPDTBT in this sample (4% BB), where almost all the ICBA appears to be fairly homogeneously dispersed in PCPDTBT. A significant change of scattering intensity is observed when the d

29、epositing solution contains CP, which is selectively soluble to ICBA, as the scat- tering intensity increases with an increase of CP concentration. This increase in scattering intensity qualitatively indicates that on

30、e component is phase separating during deposition, where the Supporting Information describes the analysis which veri- fies that the phase separated domains are ICBA. To more quantitatively analyze the scattering patter

31、ns to obtain structural information from the SANS curves, a detailed analysis of SANS curves is needed. In neutron scatting, the scatting intensity is proportional to ( b 1 – b 2 ) 2 and the form factor ( P

32、( Q )) of the scattering object, I ( Q ) ～ ( b 1 – b 2 ) 2 P ( Q ). P ( Q ) defines the shape of the scattering curve and is associated with the shape and size of domains. The scattering curves

33、of the samples in which CP is used were fit with the assumption that the form factor is modeled by the Schulz sphere model, shown in Figure 5 , which describes a two-phase system that consists of spherical domai

34、ns with a Schulz size distribution dispersed in a surrounding matrix. [ 28 ] The Schulz sphere model has been suc- cessfully used to describe the dispersion of PCBM aggregates in the P3HT rich phase of P3HT/PCBM sam

35、ples and also in the PCPDTBT rich phase of PCPDTBT/PCBM samples. [ 22,29,34 ] Using a similar analysis to that of our previous work, [ 34 ] the detailed structure of the samples is obtained. This detailed Adv. Fu

36、nct. Mater. 2014, 24, 7284–7290www.afm-journal.de www.MaterialsViews.comFigure 2. Reflectivity curves of the samples that are cast from 100% ODCB, 4%BB or 4% CP. The lines are fits to model scattering density profiles.

37、Figure 3. ICBA depth profile of AC, 4% CP and 4% BB samples as deter- mined from the reflectivity curves shown in Figure 2 and then normalized with the actual thickness of each sample.Figure 4. The absolute small angl