High Performance Organic Photovoltaic Cells Research Articles

High-performance organic photovoltaic cells under indoor lighting enabled by suppressing energetic disorders

High-performance organic photovoltaic cells under indoor lighting enabled by suppressing energetic disorders

Quantum mechanical modeling of fused rings-based small-donor molecules with enhanced optoelectronic attributes for high performance organic photovoltaic cells

Seven small molecule donors (S1–S7) have been theoretically formulated by the end-capped modeling of acceptors of reference SR. Through density functional and its time-dependent theory, different photo-physical, morphological, and opto-electronic aspects of the newly reported molecules were analyzed with reference to the SR molecule. Amongst the different studied features were the absorption maxima (λmax), transition density matrix, frontier molecular orbitals, reorganization energies of hole and electron, excitation energies, bandgaps, fill factor, and open circuit voltage (VOC), etc. Individually, the S4 molecule had the smallest bandgap and electron reorganization energy, the highest ionization potential and λmax, as well as the smallest excitation energy in the analyzed gas and chloroform phases. While the smallest interaction coefficient was seen to be of S1. The VOC of all the donor molecules computed with respect to PC61BM acceptor revealed the greatest VOC and fill factor of S1 and S4 molecules. So, it could be understood that these molecules, with special reference to S1 and S4, might outperform SR in a variety of ways, and hence are suggested to experimentalists for future innovations of organic photovoltaic cells.

Syntheses of Thiophene and Thiazole-Based Building Blocks and Their Utilization in the Syntheses of A-D-A Type Organic Semiconducting Materials with Dithienosilolo Central Unit.

Dithienosilole moiety is an electron donating unit, and it has been applied, for example, as a part of small molecular and polymeric electron donors in high performance organic photovoltaic cells. Herein, we report efficient synthetic routes to two symmetrical, dithienosilolo-central-unit-based A-D-A type organic semiconducting materials DTS(Th2FBTTh)2 and DTS(ThFBTTh)2. Fine-tuned conditions in Suzuki–Miyaura couplings were tested and utilized. The effect of inserting additional hexylthiophene structures symmetrically into the material backbone was investigated, and it was noted that contrary to commonly accepted fact, the distance between electron donor and acceptor seems to play a bigger role in lowering the Egap value of the molecule than just extending the length of the conjugated backbone. We searched for precedent cases from the literature, and these are compared to our findings. The optical properties of the materials were characterized with UV–vis spectroscopy. Majority of the intermediate compounds along the way to final products were produced with excellent yields. Our results offer highly efficient routes to many heterocyclic structures but also give new insights into the design of organic semiconducting materials.

Accurate photovoltaic measurement of organic cells for indoor applications

Yong Cui received his PhD in polymer chemistry and physics from University of Chinese Academy of Sciences in 2019. He then worked as a postdoctoral researcher at Institute of Chemistry, Chinese Academy of Sciences (ICCAS). His research interests include the study of materials and device engineering toward high-performance organic photovoltaic cells for indoor applications. Ling Hong has been a PhD student at University of Chinese Academy of Sciences since 2016. She received her BS in chemistry from Lanzhou University in 2016. Her research focuses on eco-compatible solvent-processed organic photovoltaic cells. Tao Zhang received her MS in materials chemical engineering from Anhui University of Science and Technology in 2020. Currently, she is a research assistant in ICCAS. Her research interest focuses on investigation and development of high-performance organic photovoltaic cells. Haifeng Meng received her PhD in physical chemistry from the National Center for Nanoscience and Technology in 2010. She then worked in National Institute of Metrology, China. Her research interests focus on photodetector- and photovoltaic-related metrology. He Yan is a professor at Hong Kong University of Science and Technology (HKUST). Prof Yan got his BS from Peking University in 2000, followed by a PhD from Northwestern University in 2004. His group focuses on the design and synthesis, device fabrication, and characterization of organic semiconductors that can be applied in organic solar cells, organic transistors, and detectors. Feng Gao is a professor and Wallenberg Academy Fellow at Linköping University in Sweden. He received his PhD from the University of Cambridge (UK) in 2011, followed by a Marie Skłodowska-Curie postdoc fellowship at Linköping University. His group currently focuses on research into solution-processed energy materials and devices, mainly based on organic semiconductors and metal halide perovskites. Jianhui Hou has been a professor at ICCAS since 2010 and an adjunct professor at USTB since 2012. He received his PhD in physical chemistry from ICCAS in 2006. Then he worked as a postdoctoral researcher in University of California, Los Angeles (UCLA) from 2006 to 2008 and then Director of Research of Solarmer Energy, Inc. from 2008 to 2010. His group focuses on the design, synthesis, and application of photoelectric materials.

Wide-gap non-fullerene acceptor enabling high-performance organic photovoltaic cells for indoor applications

Organic photovoltaic cells are potential candidates to drive low power consumption off-grid electronics for indoor applications. However, their power conversion efficiency is still limited by relat ...

Surface engineering of the electron collecting layers for high performance organic photovoltaic cells

Surface engineering of the electron collecting layers (ECLs) is a straightforward and practical strategy to develop high performance inverted structure organic solar cells (OSCs). Here, we systematically investigate four different types of surface modified ECLs to implement high performance low-energy band gap poly[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-bA]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl] (PTB7) and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) based inverted OSCs: (1) single PEIE, (2) ZnO:PEIE mixture (1:1 vol ratio), (3) PEIE/ZnO bilayer, and (4) ZnO/PEIE bilayer. OSCs with the ZnO/PEIE ECL show the highest power conversion efficiency (PCE) value of 8.61% while all the other devices exhibit PCE values of less than 7.80%. The excellent surface coverage as well as proper band alignment of the ZnO/PEIE bilayer leads to the highest device performance.

Orientation and crystallization of regioregular poly(3-dodecylthiophene) in alumina nanopores.

The orientation and crystallization of regioregular poly(3-dodecylthiophene) (P3DDT) in different diameter nanopores were investigated. P3DDT nanowires were prepared by a melt-wetting nonporous alumina template with P3DDT melts. The microstructure of the nanowires was analyzed by micro-Fourier transform infrared spectroscopy, grazing incidence wide angle X-ray diffraction, and differential scanning calorimetry. Although Form I modification prevails in all the nanowires, Form I crystals decrease and Form II crystals increase as the pore diameter decreases. The crystallites developed in the nanowires preferentially aligned with π-π stacking (b-axis) along the long axis of the wire and this orientation is marked as the wire diameter decreases. These results could provide guidance on designing polymeric nanomaterials for functional nanodevices in high performance organic photovoltaic cells, sensors, and electrodes.

Effects of Backbone Planarity and Tightly Packed Alkyl Chains in the Donor–Acceptor Polymers for High Photostability

The photostability of donor–acceptor (D–A) polymers remains a critical issue despite recent improvements in the power conversion efficiencies (PCEs) of organic photovoltaic (OPV) cells. We report the synthesis of three highly photostable polymers (PDTBDT-BZ, PDTBDT-BZF, and PDTBDT-BZF2) and their suitability for use in high-performance OPV cells. Under 1 sunlight of illumination in air for 10 h, these polymer films demonstrated remarkably high photostability compared to that of PTB7, a representative polymer in the OPV field. While the PDTBDT-BZ, PDTBDT-BZF, and PDTBDT-BZF2 polymer films maintained 97, 90, and 96% photostability, respectively, a PTB7 film exhibited only 38% photostability under the same conditions. We ascribed the high photostability of the polymers to both the intrinsically photostable chemical moieties and the dense packing of alkyl side chains and planar backbone polymer chains, which prevents oxygen diffusion into the PDTBDT-BZ films. This work demonstrates the high photostability of planar PDTBDT-BZ series polymers composed of photostable DTBDT and BZ moieties and suggests a design rule to synthesize highly photostable photovoltaic materials.

Controlling the Morphology of BDTT-DPP-Based Small Molecules via End-Group Functionalization for Highly Efficient Single and Tandem Organic Photovoltaic Cells.

A series of narrow-band gap, π-conjugated small molecules based on diketopyrrolopyrrole (DPP) electron acceptor units coupled with alkylthienyl-substituted-benzodithiophene (BDTT) electron donors were designed and synthesized for use as donor materials in solution-processed organic photovoltaic cells. In particular, by end-group functionalization of the small molecules with fluorine derivatives, the nanoscale morphologies of the photoactive layers of the photovoltaic cells were successfully controlled. The influences of different fluorine-based end-groups on the optoelectronic and morphological properties, carrier mobilities, and the photovoltaic performances of these materials were investigated. A high power conversion efficiency (PCE) of 6.00% under simulated solar light (AM 1.5G) illumination has been achieved for organic photovoltaic cells based on a small-molecule bulk heterojunction system consisting of a trifluoromethylbenzene (CF3) end-group-containing oligomer (BDTT-(DPP)2-CF3) as the donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the acceptor. As a result, the introduction of CF3 end-groups has been found to enhance both the short circuit current density (JSC) and fill factor (FF). A tandem photovoltaic device comprising an inverted BDTT-(DPP)2-CF3:PC71BM cell and a poly(3-hexylthiophene) (P3HT):indene-C60-bisadduct (IC60BA)-based cell as the top and bottom cell components, respectively, showed a maximum PCE of 8.30%. These results provide valuable guidelines for the rational design of conjugated small molecules for applications in high-performance organic photovoltaic cells. Furthermore, to the best of our knowledge, this is the first report on the design of fluorine-functionalized BDTT-DPP-based small molecules, which have been shown to be a viable candidate for use in inverted tandem cells.

Well-controlled thieno[3,4-c]pyrrole-4,6-(5H)-dione based conjugated polymers for high performance organic photovoltaic cells with the power conversion efficiency exceeding 9%

A series of conjugated copolymers based on a TPD moiety was synthesized as donor materials for OPVs.

Electrospun nanofibers with dual plasmonic-enhanced luminescent solar concentrator effects for high-performance organic photovoltaic cells

Dual functional electrospun nanofibers were successfully fabricated. When the plasmonic-enhanced LSC electrospun nanofibers with a crossed pattern were employed into P3HT : PC61BM and PTB7 : PC71BM, the power conversion efficiencies showed a remarkable 18% enhancement.

Towards High Performance Organic Photovoltaic Cells: A Review of Recent Development in Organic Photovoltaics

Organic photovoltaic cells (OPVs) have been a hot topic for research during the last decade due to their promising application in relieving energy pressure and environmental problems caused by the increasing combustion of fossil fuels. Much effort has been made toward understanding the photovoltaic mechanism, including evolving chemical structural motifs and designing device structures, leading to a remarkable enhancement of the power conversion efficiency of OPVs from 3% to over 15%. In this brief review, the advanced progress and the state-of-the-art performance of OPVs in very recent years are summarized. Based on several of the latest developed approaches to accurately detect the separation of electron-hole pairs in the femtosecond regime, the theoretical interpretation to exploit the comprehensive mechanistic picture of energy harvesting and charge carrier generation are discussed, especially for OPVs with bulk and multiple heterojunctions. Subsequently, the novel structural designs of the device architecture of OPVs embracing external geometry modification and intrinsic structure decoration are presented. Additionally, some approaches to further increase the efficiency of OPVs are described, including thermotics and dynamics modification methods. Finally, this review highlights the challenges and prospects with the aim of providing a better understanding towards highly efficient OPVs.

Roles of solvent additive in organic photovoltaic cells through intensity dependence of current-voltage characteristics and charge recombination

In this research, the enhanced power conversion efficiency of PBnDT-FTAZ:PC70BM bulk-heterojunction (BHJ) solar cells (over 7%), fabricated with a solvent additive (1,8-diiodooctane, 3%), was demonstrated. The appropriate ratio of solvent additive leads to a device with increased JSC, fill factor, and favorably controlled nanomorphology phase separation. Furthermore, the device with BHJ film fabricated with the solvent additive exhibited improved charge collection and simultaneously reduced charge recombination from a systematic light intensity analysis. The lack of Shockley-Read-Hall recombination at open circuit, the dominance of bimolecular recombination only when approaching open circuit, and an improved charge collection probability (95.5%) at short circuit contribute to high performance organic photovoltaic cells.

A high molecular weight triisopropylsilylethynyl (TIPS)-benzodithiophene and diketopyrrolopyrrole-based copolymer for high performance organic photovoltaic cells

A high-molecular-weight conjugated polymer consisting of alternating TIPS-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT) and diketopyrrolo[3,4-c]pyrrole (DPP) was synthesized by Suzuki cross-coupling and characterized for use in high performance OPVs. Good structural order, self-assembly in spun-cast films, and carrier mobility were observed. PTIPSBDT–DPP showed an OFET hole mobility of up to 0.12 cm2 V−1 s−1. Power conversion efficiencies of up to 8.0% were demonstrated for OPV devices.

High performance organic photovoltaic cells with blade-coated active layers

High performance bulk heterojunction organic photovoltaic (OPV) cells with blade-coated active layers of POD2T-DTBT blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) are demonstrated in this work. The blade-coated cells exhibit power conversion efficiencies of up to 6.74%, which is comparable to those of conventional spincoated cells but obtained with just a fraction of the material amount used for spincoating. The choice of solvent and the process conditions are manipulated to achieve dense, well-separated morphology which increases the interfacial area for charge dissociation in the blend film. The blade coating technique can be applied in the fabrication of large area, high performance OPV cells with highly efficient materials usage.

Self-assembled plasmonic electrodes for high-performance organic photovoltaic cells

We investigate thin Ag films incorporating plasmonic nanohole arrays as transparent conducting electrodes for organic photovoltaic cells. Plasmonic electrodes are fabricated using nanosphere lithography to create hexagonal nanohole arrays over centimeter-sized areas. Devices constructed using a nanopatterned Ag anode show power conversion efficiencies that exceed those of devices constructed on conventional indium-tin-oxide, independent of light polarization. In comparison to cells constructed on unpatterned Ag, the power conversion efficiency is noted to double with patterning.

High Performance Organic Photovoltaic Cells Using Polymer‐Hybridized ZnO Nanocrystals as a Cathode Interlayer

AbstractSolution‐processed zinc oxide nanocrystals (ZnO NCs) hybridized with insulating poly(ethylene glycol) (PEG) are introduced as a cathode interlayer in bulk heterojunction organic photovoltaic cells based on poly(3‐hexylthiophene) (P3HT):(6,6)‐phenyl‐C61 butyric acid methyl ester (PC61BM) blends. The performance of devices with ZnO‐PEG interlayers exhibit an excellent maximum power conversion efficiency (PCE) of 4.4% with a fill factor (FF) of 0.69 under optimized conditions. This enhanced device performance is attributed to decreased series resistance from the hole blocking properties of ZnO, as well as the facilitated electron transport due to the reduced area of ZnO domain boundaries upon addition of PEG. The addition of PEG also lowers the electron affinity of ZnO, which leads to a nearly Ohmic contact at the polymer/metal interface. Moreover, the ZnO‐PEG interlayer serves as an optical spacer that enhances light absorption and thereby increases the photocurrent. The addition of PEG permits control over layer thickness and refractive indices. Improved photon energy absorption is supported by optical simulations. Devices with highly stable metals such as Ag and Au also show dramatically enhanced performance comparable to conventional devices with Al cathode. Due to its simplicity and excellent characteristics, this multifunctional interlayer is suitable for high performance printed photovoltaic cells.