ABSTRACT We investigate the influence of particle plasmons on exciton and charge generation and recombination processes in the blend of poly (9‐(1‐octylnonyl)‐9H‐carbazole‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl) (PCDTBT) and [6,6]‐phenyl‐C 70 butyric acid methyl ester (PC 70 BM). The particle plasmons are generated from gold nanoparticles, which are embedded into PCDTBT:PC 70 BM blend. For the blend with gold nanoparticles, we observe enhance light harvesting. Despite the enhanced light collection, we find that the quasi‐steady‐state charge generation has not been influenced by the particle plasmons. However, the generation and recombination of long‐lived (sub‐millisecond) polaron paris have been significantly enhanced: from untrapped state in the pristine blend to the trapped state in the gold nanoparticle‐embedded blend. This result implies that the plasmon‐influenced polarons are trapped at the broadband geminate polaron pair (GPP) state. This state acts as an intermediate state, which either leads to the formation of charge transfer excitons (CTXs) or free charge carriers. In our case, the particle plasmon‐influenced polarons are trapped in the GPP state, which leads to the formation of CTXs. For this reason, we do not observe the enhanced charge generation in PCDTBT:PC 70 BM blend with particle plasmon resonance. Finally, we revealed that the long‐lived polarons mainly resulted from the localization by particle plasmons. The macroscopic modification in the blend film made negligible contributions to this influence. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 940–947

Polymer bulk heterojunction solar cells based on low bandgap polymer:fullerene blends are promising for next generation low-cost photovoltaics. While these solution-processed solar cells are compatible with large-scale roll-to-roll processing, active layers used for typical laboratory-scale devices are too thin to ensure high manufacturing yields. Furthermore, due to the limited light absorption and optical interference within the thin active layer, the external quantum efficiencies (EQEs) of bulk heterojunction polymer solar cells are severely limited. In order to produce polymer solar cells with high yields, efficient solar cells with a thick active layer must be demonstrated. In this work, the performance of thick-film solar cells employing the low-bandgap polymer poly(dithienogermole-thienopyrrolodione) (PDTG-TPD) was demonstrated. Power conversion efficiencies over 8.0% were obtained for devices with an active layer thickness of 200 nm, illustrating the potential of this polymer for large-scale manufacturing. Although an average EQE > 65% was obtained for devices with active layer thicknesses > 200 nm, the cell performance could not be maintained due to a reduction in fill factor. By comparing our results for PDTG-TPD solar cells with similar P3HT-based devices, we investigated the loss mechanisms associated with the limited device performance observed for thick-film low-bandgap polymer solar cells.

Conventional organic light emitting devices have a bottom buffer interlayer placed underneath the hole transporting layer (HTL) to improve hole injection from the indium tin oxide (ITO) electrode. In this work, a substantial enhancement in hole injection efficiency is demonstrated when an electron accepting interlayer is evaporated on top of the HTL in an inverted device along with a top hole injection anode compared with the conventional device with a bottom hole injection anode. Currentvoltage and space-charge-limited dark injection (DI-SCLC) measurements were used to characterize the conventional and inverted N,N'-diphenyl-N,N'-bis(1-naphthyl)(1,1'biphenyl)-4,4'diamine (NPB) hole-only devices with either molybdenum trioxide (MoO3) or 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN) as the interlayer. Both normal and inverted devices with HAT-CN showed significantly higher injection efficiencies compared to similar devices with MoO3, with the inverted device with HAT-CN as the interlayer showing a hole injection efficiency close to 100%. The results from doping NPB with MoO3 or HAT-CN confirmed that the injection efficiency enhancements in the inverted devices were due to the enhanced charge transfer at the electron acceptor/NPB interface.

Inverted polymer bulk heterojunction solar cells have received a great deal of attention because of their compatibility with large-scale roll-to-roll processing. The inverted cell geometry has the following structure: substrate (rigid or flexible)/indium tin oxide/electron-transporting layer/photoactive layer/hole-transporting layer/top anode. Solution-processed metal-oxide films, based on materials such as ZnO and TiO2, are typically used as the electron-transporting layers. Here, we demonstrate enhanced charge collection in inverted polymer solar cells using a surface-modified ZnO–polymer nanocomposite electron-transporting layer. Using this approach, we demonstrate inverted polymer solar cells based on a low-bandgap polymer with an alternating dithienogermole–thienopyrrolodione repeat unit (PDTG–TPD) with certified power conversion efficiencies of 7.4%. To our knowledge, this is the highest efficiency reported to date for polymer solar cells with a device architecture compatible with the roll-to-roll process. Researchers demonstrate a high-efficiency polymer solar cell whose device architecture is compatible with a large-scale roll-to-roll process. Enhanced charge collection in the inverted polymer solar cell design and certified power conversion efficiencies of around 7.4% are reported.

Advanced Energy MaterialsVolume 2, Issue 11 p. 1333-1337 Communication Inverted Polymer Solar Cells with Reduced Interface Recombination Song Chen, Song Chen Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorCephas E. Small, Cephas E. Small Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorChad M. Amb, Chad M. Amb The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, Center of Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJegadesan Subbiah, Jegadesan Subbiah Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorTzung-han Lai, Tzung-han Lai Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorSai-Wing Tsang, Sai-Wing Tsang Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJesse R. Manders, Jesse R. Manders Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJohn R. Reynolds, Corresponding Author John R. Reynolds reynolds@chemistry.gatech.edu School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA John R. Reynolds, School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA Franky So, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.Search for more papers by this authorFranky So, Corresponding Author Franky So fso@mse.ufl.edu Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA John R. Reynolds, School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA Franky So, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.Search for more papers by this author Song Chen, Song Chen Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorCephas E. Small, Cephas E. Small Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorChad M. Amb, Chad M. Amb The George and Josephine Butler Polymer Research Laboratory, Department of Chemistry, Center of Macromolecular Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJegadesan Subbiah, Jegadesan Subbiah Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorTzung-han Lai, Tzung-han Lai Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorSai-Wing Tsang, Sai-Wing Tsang Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJesse R. Manders, Jesse R. Manders Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USASearch for more papers by this authorJohn R. Reynolds, Corresponding Author John R. Reynolds reynolds@chemistry.gatech.edu School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA John R. Reynolds, School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA Franky So, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.Search for more papers by this authorFranky So, Corresponding Author Franky So fso@mse.ufl.edu Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA John R. Reynolds, School of Chemistry and Biochemistry, School of Materials Science and Engineering, Center for Organic Photonics and Electronics, Georgia Institute of Technology, Altanta, GA, 30332-0400, USA Franky So, Department of Materials Science and Engineering, University of Florida, Gainesville, Florida 32611, USA.Search for more papers by this author First published: 31 May 2012 https://doi.org/10.1002/aenm.201200184Citations: 191Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Interface recombination induced by the defect states in zinc-oxide-nanoparticle-based electron extraction layer is reported as a significant loss-mechanism of photocurrent collection. By choosing appropriate UV–ozone treatment conditions on the zinc oxide layer, inverted polymer solar cells show reduced interface recombination and thus improved power conversion efficiencies of up to 8.1%. Citing Literature Supporting Information Detailed facts of importance to specialist readers are published as "Supporting Information". Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Filename Description aenm_201200184_sm_suppl.pdf194.2 KB suppl Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article. Volume2, Issue11November, 2012Pages 1333-1337 RelatedInformation

Inverted bulk heterojunction polymer solar cells have become the preferred device architecture for roll-to-roll (R2R) processing, which allows large area devices to be fabricated on flexible substrates. Significant improvements in inverted solar cell performance have been made with novel photovoltaic polymers, along with optimized blend morphology and improved carrier extraction materials. For the first time, inverted polymer solar cells display their potential for low-cost R2R processing with power conversion efficiencies exceeding 8%.

We report the synthesis and bulk heterojunction photovoltaic performance of the first dithienogermole (DTG)-containing conjugated polymer. Stille polycondensation of a distannyl-DTG derivative with 1,3-dibromo-N-octyl-thienopyrrolodione (TPD) results in an alternating copolymer which displays light absorption extending to 735 nm, and a higher HOMO level than the analogous copolymer containing the commonly utilized dithienosilole (DTS) heterocycle. When polyDTG-TPD:PC(70)BM blends are utilized in inverted bulk heterojunction solar cells, the cells display average power conversion efficiencies of 7.3%, compared to 6.6% for the DTS-containing cells prepared in parallel under identical conditions. The performance enhancement is a result of a higher short-circuit current and fill factor in the DTG-containing cells, which comes at the cost of a slightly lower open circuit voltage than for the DTS-based cells.

The evolution of electronic energy levels of controlled air and oxygen exposed molybdenum trioxide (MoO3) films has been investigated with ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, and x-ray photoemission spectroscopy. We found that while most of the electronic levels of as deposited MoO3 films remained largely intact, the reduction in the work function (WF) was substantial. The gradual surface WF change from 6.8 to 5.3 eV was observed for air exposed film, while oxygen exposed film the surface WF saturated at ∼5.7 eV. Two distinct stages of exposure are observed, the first dominated by oxygen adsorption for <1013 Langmuir (L) exposure and at the final step moisture absorption >1013 L.