A comparison of the efficiency, stability, and photophysics of organic solar cells employing poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3'″-di(2-octyldodecyl)-2,2';5',2″;5″,2'″-quaterthiophen-5,5'″-diyl)] (PffBT4T-2OD) as a donor polymer blended with either the nonfullerene acceptor EH-IDTBR or the fullerene derivative, [6,6]-phenyl C butyric acid methyl ester (PC BM) as electron acceptors is reported. Inverted PffBT4T-2OD:EH-IDTBR blend solar cell fabricated without any processing additive achieves power conversion efficiencies (PCEs) of 9.5 ± 0.2%. The devices exhibit a high open circuit voltage of 1.08 ± 0.01 V, attributed to the high lowest unoccupied molecular orbital (LUMO) level of EH-IDTBR. Photoluminescence quenching and transient absorption data are employed to elucidate the ultrafast kinetics and efficiencies of charge separation in both blends, with PffBT4T-2OD exciton diffusion kinetics within polymer domains, and geminate recombination losses following exciton separation being identified as key factors determining the efficiency of photocurrent generation. Remarkably, while encapsulated PffBT4T-2OD:PC BM solar cells show significant efficiency loss under simulated solar irradiation ("burn in" degradation) due to the trap-assisted recombination through increased photoinduced trap states, PffBT4T-2OD:EH-IDTBR solar cell shows negligible burn in efficiency loss. Furthermore, PffBT4T-2OD:EH-IDTBR solar cells are found to be substantially more stable under 85 °C thermal stress than PffBT4T-2OD:PC BM devices.

Environmental stability is a common challenge for the commercialisation of low cost, encapsulation-free organic opto-electronic devices.

The fully printed, hole-transporter-free carbon perovskite solar cell structure incorporating a triple mesoscopic layer has emerged as a possible frontrunner for early industrialisation. It is an attractive structure because it can be fabricated by the simple sequential screen printing and sintering of titania, zirconia, and carbon. The device is finalised by manual dropping of a perovskite precursor solution onto the carbon which subsequently infiltrates. This stage in device fabrication is inhomogeneous, ineffective for large areas, and prone to human error. Here we introduce an automated deposition and infiltration system using a robotic dispenser and mesh which delivers the perovskite precursor uniformly to the carbon surface over a large area. It has been successfully used to prepare perovskite solar cells with over 9% efficiency. Cells, prepared by this robotic mesh deposition, showed comparable performance to reference cells, made by standard drop deposition, confirming this approach to be effective and reliable. X-ray diffraction and Raman spectroscopy were used to confirm the uniformity of the deposition over a large area. ARTICLE HISTORY

The fabrication of perovskite solar cells in an N-I-P structure with compact titanium dioxide blocking, mesoporous titanium dioxide scaffold, single-step perovskite and hole-transport layers deposited using the slot-die coating technique is reported. Devices on fluorine-doped tin oxide-coated glass substrates with evaporated gold top contacts and four slot-die-coated layers are demonstrated, and best cells reach stabilized power conversion efficiencies of 7%. This work demonstrates the suitability of slot-die coating for the production of layers within this perovskite solar cell stack and the potential to transfer to large area and roll-to-roll manufacturing processes.

A closed system incorporating FTIR continuous monitoring of the gas phase and a novel gas cell for the UV irradiation of flat panels of organic coatings is described. This has been used to probe various aspects of the photocatalysed degradation of TiO 2 pigmented polymer films under UVA illumination. The flat panel cell is machined from a single block of aluminium and is specifically designed to minimise dead volumes, enable rapid gas mixing and be suitable for the investigation of flat coupons of material up to 2206100 mm in size. The cell incorporates a gas input and output channel in its base feeding and fed by small bore holes drilled in such a way as to maximise the exhaustive effects on the contents of the cell. To demonstrate the effectiveness of the design the effect of TiO 2 pigment photoactivity on the rates of degradation of a commercial acrylic emulsion paint using commercial photostable TiO 2 grades is reported. In testing using this new reactor configuration it has been possible to correlate photoactivities obtained over periods of several thousand hours Xenon Arc exposure, which is the most reliable test currently available. The test cell has also been used to evaluate other coating components. Using unplasticised PVC films we have found that the rate of photogenerated CO 2 falls by up to 40% when a simple molecular UV absorber (2 hydroxybenzophenone) is added at levels of up to levels of 1 . 5% per hundred resin (PHR). Beyond this there is little further reduction in photoactivity. Finally the test cell has been used to investigate the effects of TiO 2 loading on the rates of CO 2 evolution from irradiated unplasticised PVC films pigmented with 0 -70 PHR TiO 2 . The initial rate of photodegradation (over 100 min) follows a linear trend to increased CO 2 evolution rates up to 50 PHR TiO 2 . There is a transition to a secondary rate after the production of 1 . 8 mmol m 22 of CO 2 suggesting that after a set amount of degradation there is a change in the reaction rate. This rate is still proportional to the concentration of TiO 2 . It is likely that this is due to a combination of acid catalysis and the generation of porosity in the irradiated surface, the latter enabling greater oxygen access to the irradiated TiO 2 .MST/5830

Titanium dioxide (TiO 2 ) pigment photocatalysed degradation of organic coatings and structural polymeric materials can result in polymer photodegradation and chalking. Traditional accelerated testing techniques provide comparative data on pigment performance but can take many thousands of hours to complete. In this work a new testing procedure is described that enables a rapid assessment of TiO 2 photoactivity to be made. The kinetics of CO 2 production from solution cast unplasticised PVC (UPVC) ® lms pigmented with 50% by weight TiO 2 under UV-A illumination (365 nm) monitored by Fourier transform infrared spectroscopy in a closed loop ¯ow system has been measured. A range of TiO 2 samples with differing photoactivities ranging from unclassi® ed materials (unsuitable for structural or coatings applications) through grade C (interior use), grade B (non-demanding external) and grade A (demanding external coatings and structural UPVC) have been tested. The rate of CO 2 evolution from the irradiated ® lms can be used as a photoactivity index to rank pigment photoactivity successfully within 6 h. In addition, the technique appears sensitive to differences in grade A pigment performance allowing rapid assessment of even the most photostable materials.MST/5000

A MoOx interlayer is used to enable the deposition of an ITO/Ag/ITO electrode for semi-transparent perovskite solar cells.

Building energy consumption accounts for 30%–45% of the global energy demand. With an ever-increasing world population, it has now become essential to minimize the energy consumption for the future of the environment. One of the most crucial aspects in this regard is the utilization of sensing and environmental monitoring technologies in buildings as these technologies provide stakeholders, such as owners, designers, managers, and occupants, with important information regarding the energy performance, safety and cost-effectiveness of the building. With the global sensors market value predicted to exceed $190 billion by 2021 and the number of sensors deployed worldwide forecasted to reach the ‘1 Trillion’ mark by 2025, a state-of-the-art review of various commercially-viable sensor devices and the wide range of communication technologies that complement them is highly desirable. This paper provides an insight into various sensing and environmental monitoring technologies commonly deployed in buildings by surveying different sensor technologies, wired and wireless communication technologies, and the key selection parameters and strategies for optimal sensor placement. In addition, we review the key characteristics and limitations of the most prominent battery technologies in use today, different energy harvesting sources and commercial off-the-shelf solutions, and various challenges and future perspectives associated with the application of sensing and environmental monitoring technologies within buildings.