Perovskite and organic solar cells fabricated by inkjet printing: progress and prospects

Inkjet printing (IJP) technology, adapted from home and office printing, has proven to be an essential research tool and industrial manufacturing technique in a wide range of printed electronic technologies, including optoelectronics. Its primary advantage over other deposition methods is the low-cost and maskless on-demand patterning, which offers unmatched freedom-of-design. Additional benefits include the efficient use of materials, contactless high-resolution deposition, and scalability, enabling rapid translation of learning from small-scale, laboratory-based research into large-scale industrial roll-to-roll manufacturing. In the development of organic solar cells (OSCs), IJP has enabled the printing of many of the multiple functional layers which comprise the complete cell as part of an additive printing scheme. Although IJP is only recently employed in perovskite solar cell (PeSC) fabrication, it is already showing great promise and is anticipated to find broader application with this class of materials. As OSCs and PeSCs share many common functional materials and device architectures, this review presents a progress report on the IJP of OSCs and PeSCs in order to facilitate knowledge transfer between the two technologies, with critical analyses of the challenges and opportunities also presented

Nanogenerators in Korea

Fossil fuels leaded the 21st century industrial revolution but caused some critical problems such as exhaustion of resources and global warming. Also, current power plants require too much high cost and long time for establishment and facilities to provide electricity. Thus, developing new power production systems with environmental friendliness and low-cost is critical global needs. There are some emerging energy harvesting technologies such as thermoelectric, piezoelectric, and triboelectric nanogenerators, which have great advantages on eco-friendly low-cost materials, simple fabrication, and various operating sources. Since the introduction of various energy harvesting technologies, many novel designs and applications as power suppliers and physical sensors in the world have been demonstrated based on their unique advantages. In this Special Issue, we would like to address and share basic approaches, new designs, and industrial applications related to thermoelectric, piezoelectric, and triboelectric devices which are on-going in Korea. With this Special Issue, we aim to promote fundamental understanding and to find novel ways to achieve industrial product manufacturing for energy harvesters

Multi-Layered Flexible Pressure Sensors with Tunable Sensitivity and Linearity

Department of Chemical EngineeringTunable sensitivity and linearity of flexible pressure sensors are the critical requirements for various user-friendly customized application such as wearable devices, prosthesis and smart robotics. However, flexible pressure sensors with both high sensitivity and linearity over broad pressure range have been rarely demonstrated. Here, we demonstrate a highly-sensitive and linearly-responsive flexible pressure sensor, which is achieved by multi-layering of PEDOT:PSS/PUD composites with interlocked structures. The multi-layer with different conductivity enables easy regulation of the change of composite resistance in response to the applied pressure. Multi-layered pressure sensors could linearly perceive the pressure over broad working pressure range of 100 kPa with the sensitivity of 3.1 x105 kPa-1, which is the highest one among the pressure sensors reported so far. In addition, it shows a rapid response time of 130 ms and relaxation time of 13 ms and high durability over 5000 repetitive cycles under the pressure of 20 kPa. Owing to the high sensitivity, it can discriminate weak gas flow with different air density, delicate hand manipulation of objects and different pulse rate of carotid artery and internal jugular vein.clos

Experimental study of the physics of nanostructured organic photovoltaic devices.

2012/2013Organic photovoltaic (OPV) cells based on Bulk Heterojunction (BHJ) architecture, have reached a record efficiency of 8.3% approaching the value of 10% which is considered the threshold for commercial exploitation of this technology. However, BHJ OPV cells suffer from charge collection issues, which hinder significant further increase of efficiency. A few theoretical studies have given clear indications that the most efficient nanoscale architecture consists of nano interdigitated structure of donor (D) and acceptor (A), the materials composing the active layer of OPV cells. The width of these interdigitated structures needs to be comparable to the exciton diffusion length in the two phases (10-20 nm) while their height has to be of the order of the attenuation length of the light (over 100 nm). However, obtaining this structure is challenging and in spite of the several attempts reported, the results up to date were unsuccessful. In this work an indirect approach is proposed to circumvent problems of direct top-down nanostructuring of the active layer. The idea is to nanostructure by nano imprinting lithography (NIL) an electron-blocking, hole-transporting poly(3,4-ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS) layer, a very common anode buffer layer in OPV. The reason for patterning a PEDOT:PSS layer is that it would act as: A nano interdigitated electrode with increased interface area with the donor material, for enhanced positive charges collection. A framework to guide the nanostructuring of the active layer. A diffraction grating for incident light to increase cells absorbance. However, PEDOT:PSS don't have a clear glass transition temperature and in standard lab condition the obtained structures suffer of deformation problems during stamp separation phase. For these reasons various attempts reported in literature to carry out standard thermal NIL process have led to very modest results in terms of aspect ratio and structure quality. Therefore, we investigated a modified NIL process, Water Vapour Assisted NIL (WVA-NIL), based on the accurate control of the environmental relative humidity to influence mechanical properties of PEDOT:PSS. After process optimization, we were able to fabricate sub-100 nm features in PEDOT:PSS with high aspect ratios (up to 6). WVA-NIL process resulted also to be able to modify, in a controlled and reproducible way, the electronic properties of the material, leading to a conductivity increase up to 5 orders of magnitude and a decrease in work function (Ф) up to 1.5 eV. This open new opportunities to tune PEDOT:PSS properties for specific application, and even for use as cathode instead of anode in OPV. We have investigated the possibility to fabricate nanostructured OPV cells by conformal coating and/or infiltration of PEDOT:PSS nanostructures with different organic semiconductors, either by thermal vacuum evaporation or solution processing, with the purpose of implementing two main architectures consisting of: 1. A nano interdigitated A/D structure, obtained by conformal deposition of the donor material on PEDOT:PSS structures, followed by infiltration with the acceptor material. 2. A BHJ cell with an interdigitated electrode, obtained infiltrating the PEDOT:PSS structures with a blend of the two active materials. As donor materials we tested Poly[2,7-(9,9-dioctyl-dibenzosilole)-alt-4,7-bis(thiophen-2- yl)benzo-2,1,3-thiadiazole] (PSiF-DBT), poly(3-hexylthiophene) (P3HT), pentacene, copper phthalocyanine (CuPc). As acceptor materials were tested: C60; phenyl-C61-butyric acid methyl ester (PCBM); indene-C60 bisadduct (ICBA). Nano interdigitated structures of aspect ratios up to 2 were successfully implemented according to architecture 1, using the combination of Pentacene and PCBM, while the main issues and limitations using the other materials were identified. The architecture 2 was successfully implemented with P3HT-ICBA and P3HT-PCBM BHJ on PEDOT:PSS gratings of lines. From the testing of the obtained cells, the most promising system resulted to be the architecture 2. Nanopatterned P3HT-ICBA BHJ cells have shown a 60% relative increase of efficiency compared to flat BHJ reference cells (in absolute values 1.3% vs 0.8% efficiency). Additional experiments were performed on the hybrid system PSiF-DBT/CuInS2, with a nano interdigitated structure of the two materials. This structure was implemented by NIL processing of PSiF-DBT, followed by an infiltration of the obtained structures with copper and indium xanthates, precursor materials that can be thermally converted into CuInS2. The nano interdigitated structure was successfully obtained, and a first series of cell was produced, showing a more than doubled efficiency, starting from 0.13% of a flat bi-layer cell to 0.30% of the nanostructured one, for thermal conversion performed at 160°C.---------------------RIASSUNTO IN ITALIANO------------------------------ Le celle fotovoltaiche organiche (OPV) basate sull’architettura “Bulk Heterojunction” (BHJ) hanno raggiunto un record di efficienza del 8,3%, avvicinandosi al 10%, considerato soglia da superare per lo sfruttamento commerciale di questa tecnologia. Tuttavia, le celle fotovoltaiche organiche BHJ soffrono di problemi di raccolta di carica, che impediscono di ottenere ulteriori significativi incrementi di efficienza. Alcuni studi teorici hanno dato chiare indicazioni sul fatto che, la più efficiente nano architettura per le celle fotovoltaiche organiche, consiste in una struttura interdigitata di donore (D) ed accettore (A), i due materiali che compongono lo strato attivo delle celle fotovoltaiche organiche. La larghezza di queste strutture interdigitate deve essere comparabile alla distanza di diffusione degli eccitoni nelle due fasi (10-20 nm), mentre la loro altezza deve essere dell’ordine della lunghezza di attenuazione della luce nel materiale (più di 100 nm). Tuttavia ottenere queste strutture è complesso e nonostante diversi tentativi riportati in letteratura, fino ad ora non si sono ottenuti risultati soddisfacenti. In questo lavoro viene proposto un approccio indiretto che aggira i problemi della nano strutturazione “top-down” dello strato attivo. L’idea è di nano strutturare mediante ”nano imprinting lithography“ (NIL) un film di poly(3,4- ethylenedioxythiophene): poly(4-styrenesulfonate) (PEDOT:PSS), comune strato intermedio anodico delle celle fotovoltaiche organiche. La nano struttura di PEDOT:PSS così ottenuta agirà da: Elettrodo nano interdigitato ad elevata interfaccia di contatto con il materiale donore, per facilitare la raccolta di cariche positive. Da ossatura per guidare la nano strutturazione dello strato attivo. Da reticolo di diffrazione per la luce in modo da incrementare l’assorbimento della cella. Tuttavia il PEDOT:PSS non ha una chiara temperatura di transizione vetrosa, ed in condizioni di laboratorio standard, le strutture soffrono di problemi di deformazione durante la fase di separazione dello stampo. Per questo motivo vari tentativi riportati in letteratura di utilizzare il processo NIL termico standard, hanno portato a risultati modesti in termini di rapporto di forma e qualità delle strutture. Abbiamo quindi studiato un processo NIL modificato, Water Vapour Assisted NIL (WVA-NIL), basato su un'accurato controllo dell’umidità relativa ambientale al fine di influire sulle proprietà meccaniche del PEDOT:PPS. A seguito dell’ottimizzazione del processo siamo stati in grado di fabbricare strutture con dettagli sub-100 nm e con elevato rapporto di forma (fino a 6). Il processo WVA-NIL è inoltre risultato in grado di modificare in modo controllato e riproducibile le proprietà elettroniche del materiale, portando ad un incremento di conducibilità fino a 5 ordini di grandezza ed una riduzione di funzione lavoro (Ф) fino a 1.5 eV. Questo apre la possibilità di regolare le proprietà elettroniche del PEDOT:PSS per applicazioni specifiche, ed addirittura usarlo come catodo anziché come anodo nelle celle OPV. Abbiamo studiato la possibilità di ottenere celle OPV nano strutturate con una deposizione conformale ed/o infiltrazione delle strutture di PEDOT:SS con diversi semiconduttori organici, depositati per evaporazione termica a vuoto o per deposizione da soluzione. Lo scopo di ciò è di ottenere due principali architetture: 1. Una struttura nano interdigitata A/D ottenuta per deposizione conformale del materiale donore sulle strutture di PEDOT:PSS, seguita da infiltrazione con materiale accettore. 2. Una cella BHJ, con un elettrodo interdigitato, ottenuta infiltrando le strutture in PEDOT:PSS con una mistura dei due materiali attivi. Come materiali donori abbiamo testato: Poly[2,7-(9,9-dioctyl-dibenzosilole)-alt-4,7- bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT); poly(3-hexylthiophene) (P3HT); pentacene; ftalocianine di rame (CuPc). Come materiali accettori: C60; phenyl-C61-butyric acid methyl ester (PCBM); indene-C60 bisadduct (ICBA). Strutture nano interdigitate con aspetto di forma fino a 2 sono state ottenute con successo, secondo l’architettura 1, usando la combinazione di materiali Pentacene-PCBM mentre i principali problemi e limitazioni nell’utilizzo degli altri materiali sono stati identificati. La seconda architettura è stata implementata con successo con celle BHJ in P3HT-ICBA e P3HT PCBM, usando reticoli di linee di PEDOT:PSS. Dai test di caratterizzazione delle celle è emerso che il sistema più promettente è costituito dalla architettura 2. Celle BHJ P3HT-ICBA nano strutturate hanno mostrato un aumento relativo di efficienza del 60% confrontate ad una cella BHJ di riferimento planare (in valore assoluto 1,3% contro 0.8%). Sono stati eseguiti anche esperimenti su celle nano interdigitate ibride in PSiF- DBT/CuInS 2 . Questa struttura è stata ottenuta mediate processo NIL del PSiF-DBT, seguito da infiltrazione con xantati di indio e rame, precursori che possono essere convertiti termicamente in CuInS 2 . La struttura nano interdigitata è stata ottenuta con successo e dalla prima serie di celle prodotta, ha mostrato un raddoppio dell’efficienza, passando da 0,13%XXVI Ciclo198

High-Throughput, Continuous Nanopatterning Technologies for Display and Energy Applications.

The motivation of this work is to enable continuous patterning of nanostructures on flexible substrates to push nanoscale lithography to an entirely new level with drastically increased throughput. The Roll-to-Roll Nanoimprint Lithography (R2RNIL) technology presented in this work retains the high-resolution feature capabilities of traditional NIL, but with an increase in throughput by at least one or two orders of magnitude. We demonstrated large-area (4” wide) continuous imprinting of nanogratings by using a newly developed apparatus capable of roll-to-roll imprinting on flexible substrates (R2RNIL) and roll-to-plate imprinting on rigid substrates (R2PNIL). In addition, analytical models were developed to predict the residual layer thickness in dynamic R2RNIL. As a potential application, high-performance metal wire-grid polarizers have also been fabricated utilizing R2RNIL. Another research focus involved Direct Metal Imprinting (DMI) to create discrete nano-scale metal gratings. DMI uses a polymer cushion layer between a thin metal layer and a hard substrate, which enables room-temperature nanoimprinting of the metal by overcoming troublesome hard-to-hard surface contact issues while preserving the Si mold. We also introduced a novel nanofabrication technique, Dynamic Nano-Inscribing (DNI) for creating truly continuous nanograting patterns by using the sharp edge of a tilted Si mold on a variety of metals or polymer materials, creating linewidths down to 50 nm at extremely high speeds (~100 mm/sec) under ambient conditions. Additionally, a new nanograting fabrication method, Localized Dynamic Wrinkling (LDW) has been developed. LDW enables the continuous formation of micro/nano-scale gratings by simply sliding a flat edge of a cleaved Si wafer over the metal film. LDW shares the same basic principle as the buckling (wrinkling) phenomenon but the moving edge of the tilted Si wafer exerts stress on a metal coated polymer and sequentially generates localized winkles in the metal film in a dynamic fashion. The period in LDW can be controlled by several processing parameters and shows good agreement with a theoretical model. Finally, we developed a Dynamic Nano-Cutting (DNC) process using high-frequency indentations on a moving substrate to sequentially create nanograting patterns. DNC provides perfectly straight lines with real-time period modulation, which is difficult to achieve by other nanomanufacturing techniques.Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/76015/1/happyash_1.pd

A review on materials and technologies for organic large-area electronics

New and innovative applications in the field of electronics are rapidly emerging. Such applications often require flexible or stretchable substrates, lightweight and transparent materials, and design freedom. This paper offers a complete overview concerning flexible electronics manufacturing, focusing on the materials and technologies that have been recently developed. This combination of materials and technologies aims to fuel a fast, economical, and environmentally sustainable transition from the conventional to the novel and highly customizable electronics. Organic conductors, semiconductors, and dielectrics have recently gathered lots of attention since they are compatible with printing technologies, and can be easily spread over large and flexible substrates. These printing technologies are usually simple and fast procedures, which rely on low-cost and recycle-friendly materials, intended for large-scale fabrication. Overall, even though organic large-area electronics manufacturing is still in its early stages of development, it is a field with tremendous potential that holds promise to revolutionize the way products are designed, developed, and processed from the factory premises to the consumers’ hands. Besides, this technology is highly versatile and can be applied to a large array of sectors such as automotive, medical, home design, industrial, agricultural, among others.This work was supported by NORTE-06-3559-FSE-000018, integrated in the invitation NORTE-59-2018-41, aiming the Hiring of Highly Qualified Human Resources, co-financed by the Regional Operational Programme of the North 2020, thematic area of Competitiveness and Employment, through the European Social Fund (ESF), and by the scope of projects with references UIDB/05256/2020 and UIDP/05256/2020, financed by FCT – Fundação para a Ciência e Tecnologia, Portugal. The authors also thank Prof. Luís A. Rocha for his support and guidance during the writing of this review work

Organic photodiodes: printing, coating, benchmarks, and applications

Organic photodiodes (OPDs) are set to enhance traditional optical detection technologies and open new fields of applications, through the addition of functionalities such as wavelength tunability, mechanical flexibility, light-weight or transparency. This, in combination with printing and coating technology will contribute to the development of cost-effective production methods for optical detection systems. In this review, we compile the current progress in the development of OPDs fabricated with the help of industrial relevant coating and printing techniques. We review their working principle and their figures-of-merit (FOM) highlighting the top device performances through a comparison of material systems and processing approaches. We place particular emphasis in discussing methodologies, processing steps and architectural design that lead to improved FOM. Finally, we survey the current applications of OPDs in which printing technology have enabled technological developments while discussing future trends and needs for improvement

Organic Thin Film Transistor Integration

This thesis examines strategies to exploit existing materials and techniques to advance organic thin film transistor (OTFT) technology in device performance, device manufacture, and device integration. To enhance device performance, optimization of plasma enhanced chemical vapor deposited (PECVD) gate dielectric thin film and investigation of interface engineering methodologies are explored. To advance device manufacture, OTFT fabrication strategies are developed to enable organic circuit integration. Progress in device integration is achieved through demonstration of OTFT integration into functional circuits for applications such as active-matrix displays and radio frequency identification (RFID) tags. OTFT integration schemes featuring a tailored OTFT-compatible photolithography process and a hybrid photolithography-inkjet printing process are developed. They enable the fabrication of fully-patterned and fully-encapsulated OTFTs and circuits. Research on improving device performance of bottom-gate bottom-contact poly(3,3'''-dialkyl-quarter-thiophene) (PQT-12) OTFTs on PECVD silicon nitride (SiNx) gate dielectric leads to the following key conclusions: (a) increasing silicon content in SiNx gate dielectric leads to enhancement in field-effect mobility and on/off current ratio; (b) surface treatment of SiNx gate dielectric with a combination of O2 plasma and octyltrichlorosilane (OTS) self-assembled monolayer (SAM) delivers the best OTFT performance; (c) an optimal O2 plasma treatment duration exists for attaining highest field-effect mobility and is linked to a “turn-around” effect; and (d) surface treatment of the gold (Au) source/drain contacts by 1-octanethiol SAM limits mobility and should be omitted. There is a strong correlation between the electrical characteristics and the interfacial characteristics of OTFTs. In particular, the device mobility is influenced by the interplay of various interfacial mechanisms, including surface energy, surface roughness, and chemical composition. Finally, the collective knowledge from these investigations facilitates the integration of OTFTs into organic circuits, which is expected to contribute to the development of new generation of all-organic displays for communication devices and other pertinent applications. A major outcome of this work is that it provides an economical means for organic transistor and circuit integration, by enabling use of the well-established PECVD infrastructure, yet not compromising the performance of electronics

A new architecture as transparent electrodes for solar and IR applications based on photonic structures via soft lithography

Transparent conducting electrodes with the combination of high optical transmission and good electrical conductivity are essential for solar energy harvesting and electric lighting devices. Currently, indium tin oxide (ITO) is used because ITO offers relatively high transparency (\u3e80%) to visible light and low sheet resistance (Rs = 10 ohms/square) for electrical conduction. However, ITO is costly due to limited indium reserves, and it is brittle. These disadvantages have motivated the search for other conducting electrodes with similar or better properties. There has been research on a variety of electrode structures involving carbon nanotube networks, graphene films, nanowire and nanopatterned meshes and grids. Due to their novel characteristics in light manipulation and collection, photonic crystal structures show promise for further improvement. Here, we report on a new architecture consisting of nanoscale high aspect ratio metallic photonic structures as transparent electrodes fabricated via a combination of processes. For (Au) and silver (Ag) structures, the visible light transmission can reach as high as 80%, and the sheet resistance of the structure can be as low as 3.2 ohms/square. The optical transparency of the high aspect ratio metal structures at visible wavelength range is comparable to that of ITO glass, while their sheet resistance is more than 3 times lower, which indicates a much higher electrical conductivity of the metal structures. Furthermore, the high aspect ratio metal structures have very high infrared (IR) reflection (90%) for the transverse magnetic (TM) mode, which can lead to the development of fabrication of metallic structures as IR filters for heat control applications. Investigations of interdigitated structures based on the high aspect ratio metal electrodes are ongoing to study the feasibility in smart window applications in light transmission modulation