• Energy Research

Abstract The recent development of 5G networks has enabled the internet of things (IoT) to emerge as a key factor in the growing global data network. For the IoT, not only are sensors required, but also alternative ways to supply them with the energy they need. Organic photovoltaics (OPV) are a promising solution for energy harvesting and self-generation for low-consumption sensors since they have excellent physical, optical and electrical properties, including being lightweight, having shape freedom, broad-range absorption spectra, semi-transparency, and they are highly efficient even in extremely low-light environments. Here, we report, encapsulated OPV module optimized for indoor applications delivering 18% power conversion efficiency (PCE) under 400 lx LED illumination. All modules were fabricated and encapsulated in air using totally scalable roll-to-roll (R2R) slot-die coating and screen-printing methods made on flexible substrates with non-toxic solvents.

AbstractPaper is a flexible material, commonly used for information storage, writing, packaging, or specialized purposes. It also has strong appeal as a substrate in the field of flexible printed electronics. Many applications, including safety, merchandising, smart labels/packing, and chemical/biomedical sensors, require an energy source to power operation. Here, progress regarding development of photovoltaic and energy storage devices on cellulosic substrates, where one or more of the main material layers are deposited via solution processing or printing, is reviewed. Paper can be used simply as the flexible substrate or, exploiting its porous fiber‐like nature, as an active film by infiltration or copreparation with electronic materials. Solar cells with efficiencies of up to 9% on opaque substrates and 13% on transparent substrates are demonstrated. Recent developments in paper‐based supercapacitors and batteries are also reviewed with maximum achieved capacity of 1350 mF cm−2and 2000 mAh g−1, respectively. Analyzing the literature, it becomes apparent that more work needs to be carried out in continuing to improve peak performance, but especially stability and the application of printing techniques, even roll‐to‐roll processing, over large areas. Paper is not only environmentally friendly and recyclable, but also thin, flexible, lightweight, biocompatible, and inexpensive.

Abstract We present new architectures in CH3NH3PbI3 based planar perovskite solar cells incorporating solution processed SnO2/MgO composite electron transport layers that show the highest power outputs ever reported for photovoltaic cells under typical 200–400 lx indoor illumination conditions. When measured under white OSRAM LED lamp (200, 400 lx), the maximum power density values were 20.2 µW/cm2 (estimated power conversion efficiency, PCE = 25.0%) at 200 lx and 41.6 µW/cm2 (PCE = 26.9%) at 400 lx which correspond to a ∼ 20% increment compared to solar cells with a SnO2 layer only (even at standard 1 sun illumination, where the maximum PCE was 19.0%). The thin MgO overlayer leads to more uniform films, reduces interfacial carrier recombination, and leads to better stability. All layers of the cells, except for the two electrodes, are solution processed at low temperatures for low cost processing. Furthermore, ambient indoor conditions represent a milder environment compared to stringent outdoor conditions for a technology that is still looking for a commercial outlet also due to stability concerns. The unparalleled performance here demonstrated, paves the way for perovskite solar cells to contribute strongly to the powering of the indoor electronics of the future (e.g. smart autonomous indoor wireless sensor networks, internet of things etc).

We present planar perovskite solar cells incorporating thin SnO2/Al2O3 double electron transport layers between the perovskite and an indium tin oxide bottom electrode. When measured under 1 sun illumination, we obtained a maximum power conversion efficiency (PCE) of 20.1% and a steady state efficiency of 17.8% for the best cell. These values were ∼20%–30% higher in relative terms than those of cells with SnO2 only (i.e., a maximum PCE of 15.3% and a steady state PCE of 14.9%). Insertion of the thin UV-irradiated solution-processed nanoparticle Al2O3 interlayer effectively enhanced the wettability of the electron transport layer, provided enhanced interface area, as well as a lower work function, leading to improved charge extraction. Incorporation of an Al2O3 layer between the perovskite and SnO2 layers also improved the rectification ratios of the diodes as well as both series and shunt resistances. Our devices are fabricated using fully solution-processed transport and active semiconducting layers processed at low temperatures (≤150 °C).

Summary: The internet of things revolution requires efficient, easy-to-integrate energy harvesting. Here, we report indoor power generation by flexible perovskite solar cells (PSCs) manufactured on roll-to-roll indium-doped tin oxide (ITO)-coated ultra-thin flexible glass (FG) substrates with notable transmittance (>80%), sheet resistance (13 Ω/square), and bendability, surpassing 1,600 bending procedures at 20.5-mm curvature. Optimized PSCs on FG incorporate a mesoporous scaffold over SnO2 compact layers delivering efficiencies of 20.6% (16.7 μW⋅cm−2 power density) and 22.6% (35.0 μW⋅cm−2) under 200 and 400 lx LED illumination, respectively. These represent, to the best of our knowledge, the highest reported for any indoor flexible solar cell technology, surpassing by a 60%–90% margin the prior best-performing flexible PSCs. Specific powers (W/g) delivered by these lightweight cells are 40%–55% higher than their counterparts on polyethylene terephthalate (PET) films and an order of magnitude greater than those on rigid glass, highlighting the potential of flexible FG-PSCs as a key enabling technology for powering indoor electronics of the future.