Flexible Solution-Processed Electron-Transport-Layer-Free Organic Photovoltaics for Indoor Application.

Organic photovoltaics (OPVs) have unique advantages of low weight, mechanical flexibility, and solution processability, which make them exceptionally suitable for integrating low-power Internet of Things devices. However, achieving improved operational stability together with solution processes that are applicable to large-scale fabrication remains challenging. Their major limitation arises due to the instable factors that occur both inside the thick active film and from the ambient environment, which cannot be completely resolved via the current encapsulation techniques used for flexible OPVs. Additionally, thin active layers are highly vulnerable to point defects, which result in low yield rates and impede the laboratory-to-industry translation. In this study, flexible fully solution-processed OPVs with improved indoor efficiency and long-term operational stability than that of conventional OPVs with evaporated electrodes are achieved. Benefiting from the oxygen and water vapor permeation barrier of the spontaneously formed gallium oxide layers on the exposed eutectic gallium-indium surface, fast degradation of the OPVs with thick active layers is prevented, maintaining 93% of its initial Pmax after 5000 min of indoor operation under 1000 lx light-emitting diode (LED) illumination. Additionally, by using the thick active layer, spin-coated silver nanowires could be directly used as bottom electrodes without complicated flattening processes, thereby substantially simplifying the fabrication process and proposing a promising manufacturing technique for devices with high-throughput energy demands.

p-Tetrafluorophenylene Divinylene-Bridged Nonfullerene Acceptors as Binary Components or Additives for High-Efficiency Organic Solar Cells.

In this study, we designed, synthesized, and characterized an A-D-A'-D-A-type indacenodithienothiophene (IDTT)-based molecular acceptor that exhibited a broader absorption range and higher lowest unoccupied molecular orbital energy level with a nearly comparable band gap compared to a well-known electron acceptor IT-M. The designed electron-deficient molecular acceptor FB-2IDTT-4Cl with a fluorinated benzene tether (FB), that is, p-tetrafluorophenylene divinylene, demonstrated long-wavelength absorption and high hole and electron charge mobility in the thin films blended with the electron donor PBDB-T for an inverted organic photovoltaic (OPV) binary device, resulting in a maximum power conversion efficiency (PCE) of 11.4%. Such a performance is comparably as high as that of the device with PBDB-T:IT-M, and particularly, it was 18.8% higher than that of the devices with ITIC-4Cl as the acceptor (PCE 9.1% ± 0.5%) and 24.9% higher than that of the devices with the thiophene-flanked benzothiadiazole-bridged acceptor CNDTBT-IDTT-FINCN (PCE 9.01% ± 0.13%). Furthermore, varying the illumination intensity from 200 to 2000 lux increased the Jsc and Voc values as well as the FF values, thus leading to increased PCE levels. In addition, the best PCE of the PM6:Y6 device with 1% FB-2IDTT-4Cl as additives was 16.9%. Our stability test showed that the PM6:Y6 standard device efficiency downgraded very soon either at room temperature or under thermal-annealing conditions. However, with the addition of 1% FB-2IDTT-4Cl as additives, the device efficiency still can be maintained at 90-95% in 500 h at room temperature and 95% at 20 h and 85-95% in 45 h at an annealing temperature of 80 °C. These findings demonstrate FB-2IDTT-4Cl to be a promising candidate as an electron acceptor with a fluorinated π-bridging fused-ring design for OPV applications.

Elucidating End-Group Modifications of Carbazole-Based Nonfullerene Acceptors in Indoor Applications for Achieving a PCE of over 20.

In this work, two DTSiC-based nonfullerene acceptors (NFAs), (2,2'-((2Z,2'Z)-((12-(heptadecan-9-yl)-4,4,7,7-tetraoctyl-7,12-dihydro-4H-thieno[2',3':4,5]silolo[3,2-b]thieno[2',3':4,5]silolo[2,3-h]carbazole-2,9-diyl)bis(methaneylylidene))bis(3-oxo-2,3-dihydro-1H-indene-2,1-diylidene))dimalononitrile) (DTSiC-IC) and (2,2'-((5Z,5'Z)-((12-(heptadecan-9-yl)-4,4,7,7-tetraoctyl-7,12-dihydro-4H-thieno[2',3':4,5]silolo[3,2-b]thieno[2',3':4,5]silolo[2,3-h]carbazole-2,9-diyl)bis(methaneylylidene))bis(6-oxo-5,6-dihydro-4H-cyclopenta[c]thiophene-5,4-diylidene))dimalononitrile) (DTSiC-TC), are designed with various end groups (IC and TC). To explore the effect of end-group modifications, photovoltaic performance under AM 1.5G and indoor conditions are comprehensively studied. Compared with DTSiC-IC, DTSiC-TC manifests red-shifted and stronger absorption, downshifted lowest unoccupied molecular orbital (LUMO), and pronounced face-on packing characteristics. As we envisaged, the PM7:DTSiC-TC-based devices outperform the PM7:DTSiC-IC-based devices in both AM 1.5G and indoor (light-emitting diode (LED) 3000 K 1000 lux) conditions with overall higher JSC, FF, and power conversion efficiency (PCE). Furthermore, the PM7:DTSiC-TC-based devices achieve an outstanding PCE of 20.73% with a VOC of 0.87 V, a JSC of 0.095 mA/cm2, and an FF of 70.86%.

A New Conjugated Polymer that Enables the Integration of Photovoltaic and Light-Emitting Functions in One Device.

Exploring the intriguing bifunctional nature of organic semiconductors and investigating the feasibility of fabricating bifunctional devices are of great significance in realizing various applications with one device. Here, the design of a new wide-bandgap polymer named PBQx-TCl (optical bandgap of 2.05 eV) is reported, and its applications in photovoltaic and light-emitting devices are studied. By fabricating devices with nonfullerene acceptors BTA3 and BTP-eC9, it is shown that the devices exhibit a high power conversion efficiency (PCE) of 18.0% under air mass 1.5G illumination conditions and an outstanding PCE of 28.5% for a 1 cm2 device and 26.0% for a 10 cm2 device under illumination from a 1000 lux light-emitting diode. In addition, the PBQx-TCl:BTA3-based device also demonstrates a moderate organic light-emitting diode performance with an electroluminescence external quantum efficiency approaching 0.2% and a broad emission range of 630-1000 nm. These results suggest that the polymer PBQx-TCl-based devices exhibit outstanding photovoltaic performance and potential light-emitting functions.

Organic Photovoltaic Cells for Indoor Applications: Opportunities and Challenges.

With the growing development of the Internet of Things, organic photovoltaic (OPV) cells are highly desirable for indoor applications because of the unique features of light weight, flexibility, and coloration. Emission spectra of the commonly used indoor light sources are much narrower with lower light intensity as compared to the standard solar spectrum. High tunability in optical absorption, insensitivity to series resistance and the active layer thickness, and mild operating conditions make indoor OPV cells promising as a practically relevant technology. Currently, the OPV module has obtained a power conversion efficiency of over 20%, with excellent stability under indoor conditions. However, at the present stage, the device physics investigations and material design strategies developed in an OPV cell for indoor applications lag behind those for outdoor applications. In particular, the emerging characterizations in photovoltaic measurements have severely affected the reliability of reports. This Spotlight on Applications highlights these opportunities and challenges of OPV cells for indoor applications and reviews the recent progress in indoor OPV cells. In addition, we summarize some studies related to accurate measurement and provide some recommendations.

Realizing Stable Artificial Photon Energy Harvesting Based on Perovskite Solar Cells for Diverse Applications.

As the fastest developing photovoltaic device, perovskite solar cells have achieved an extraordinary power conversion efficiency (PCE) of 25.3% under AM 1.5 illumination. However, few studies have been devoted to perovskite solar cells harvesting artificial light, owing to the great challenge in the simultaneous manipulation of bandgap-adjustable perovskite materials, corresponding matched energy band structure of carrier transport materials, and interfacial defects. Herein, through systematic morphology, composition, and energy band engineering, high-quality Cs0.05 MA0.95 PbBrx I3- x perovskite as the light absorber and Nby Ti1- y O2 (Nb:TiO2 ) as the electron transport material with an ideal energy band alignment are obtained simultaneously. The theoretical-limit-approaching record PCEs of 36.3% (average: 34.0 ± 1.2%) under light-emitting diode (LED, warm white) and 33.2% under fluorescent lamp (cold white) are achieved simultaneously, as well as a PCE of 19.5% (average: 18.9 ± 0.3%) under solar illumination. An integrated energy conversion and storage system based on an artificial light response solar cell and sodium-ion battery is established for diverse practical applications, including a portable calculator, quartz clock, and even environmental monitoring equipment. Over a week of stable operation shows its great practical potential and provides a new avenue to promote the commercialization of perovskite photovoltaic devices via integration with ingenious electronic devices.

1 cm2 Organic Photovoltaic Cells for Indoor Application with over 20% Efficiency.

Organic photovoltaic (OPV) technologies have the advantages of fabricating larger-area and light-weight solar panels on flexible substrates by low-cost roll-to-toll production. Recently, OPV cells have achieved many significant advances with power conversion efficiency (PCE) increasing rapidly. However, large-scale solar farms using OPV modules still face great challenges, such as device stability. Herein, the applications of OPV cells in indoor light environments are studied. Via optimizing the active layers to have a good match with the indoor light source, 1 cm2 OPV cells are fabricated and a top PCE of 22% under 1000 lux light-emitting diode (2700 K) illumination is demonstrated. In this work, the light intensities are measured carefully. Incorporated with the external quantum efficiency and photon flux spectrum, the integral current densities of the cells are calculated to confirm the reliability of the photovoltaic measurement. In addition, the devices show much better stability under continuous indoor light illumination. The results suggest that designing wide-bandgap active materials to meet the requirements for the indoor OPV cells has a great potential in achieving higher photovoltaic performance.

Persistence of malathion used in dengue control on household surfaces / Permanência do malathion usado no controle da dengue em superfícies domiciliares

Dengue is a viral infection transmitted by the mosquito Aedes aegypti. In Brazil, one of the insecticides used to control the mosquito is malathion, which can be diluted in vegetable oil (1:2 v/v). The purpose of this study was to understand the persistence of malathion on different surfaces and soil. Surfaces were contaminated by malathion and then washed with water and soap. The water used to clean the surfaces was extracted and analyzed by gas chromatography with an FID detector. Soil samples received malathion 14C-TG diluted in vegetable oil (1:2 v/v) and were analyzed zero, 3, 7, 18, 32, 60, 120, 240, and 360 days after the application in a liquid scintillation analyzer. Results showed a high persistence of malathion on porous surfaces. Moreover, it did not degrade in the soil for the first 120 days.(AU)

A dengue é uma infecção viral transmitida pelo mosquito Aedes aegypti. No Brasil, um dos inseticidas utilizados para controlar o mosquito é o malathion, que pode ser diluído em óleo vegetal (1:2 v/v). O objetivo deste trabalho foi avaliar a permanência do malathion em diferentes superfícies e no solo. As superfícies foram contaminadas com malathion e depois lavadas com água e sabão. A água utilizada para limpar as superfícies foi extraída e analisada por cromatografia gasosa com detector de ionização de chama. O malathion 14C-GT diluído em óleo vegetal (1:2 v/v) foi aplicado em amostras de solo que foram analisadas nos tempos 0, 3, 7, 18, 32, 60, 120, 240 e 360 dias após a aplicação, em um analisador de cintilação líquida. Os resultados mostraram alta permanência de malathion em superfícies porosas. Além disso, o malathion não se degradou no solo nos primeiros 120 dias.(AU)