A new species of the amphipod genus Quadrivisio (Senticaudata, Maeridae) from Chilika Lagoon, India.

A new species of the amphipod genus Quadrivisio Stebbing, 1907, Quadrivisio chilikensis sp. nov. was collected from the Chilika Lagoon, east coast of India. The species was collected from seaweed Chaetomorpha sp.. The new species can be distinguished from other described species of the genus by the presence of a carina on pleonites and urosome, by the flagellum of antenna 2 being twice the length of peduncle article 5 and by pereopods 6 and 7 being equal in length.

Organic Dye/Cs2AgBiBr6 Double Perovskite Heterojunction Solar Cells.

The photovoltaic performance of Cs2AgBiBr6 perovskite is limited by its light-harvesting ability owing to its broad bandgap. Here, we introduced three indoline dyes, D102, D131, and D149, to sensitize the TiO2 electron transport layer that was employed in the Cs2AgBiBr6 perovskite solar cells (PSCs). The perovskite-indoline dye hybrid cells worked with higher power conversion efficiencies (PCEs) than the corresponding dye-sensitized solar cells and the PSC. Extended absorption resulted in a higher short-circuit current density, up to 8.24 mA cm-2, and a maximum PCE of 4.23% in the case of D149, for instance. The double perovskite worked as a p-type interlayer between the dyes and spiro-OMeTAD to convey the holes from the former to the latter, resulting in enhancement in the overall performance.

Chlorophyll Derivative-Sensitized TiO2 Electron Transport Layer for Record Efficiency of Cs2AgBiBr6 Double Perovskite Solar Cells.

The power conversion efficiency (PCE) of Cs2AgBiBr6-based perovskite solar cells (PSCs) is still low owing to the inherent defects of Cs2AgBiBr6 films. Herein, we demonstrate a carboxy-chlorophyll derivative (C-Chl)-sensitized mesoporous TiO2 (m-TiO2) film as an electron transport layer (ETL) to enhance and extend the absorption spectrum of Cs2AgBiBr6-based PSCs. The C-Chl-based device achieves a significantly improved PCE, exceeding 3% for the first time, with an increase of 27% in short-circuit current density. Optoelectronic investigations confirm that the introduction of C-Chl reduces the defects, accelerates the electron extraction, and suppresses charge recombination at the interface of ETL/perovskite. Moreover, the unencapsulated PSCs display restrained hysteresis and great stability under ambient conditions.

Cesium Acetate-Induced Interfacial Compositional Change and Graded Band Level in MAPbI3 Perovskite Solar Cells.

Compositional engineering and interfacial modifications have played pivotal roles in the accomplishment of high-efficiency perovskite solar cells (PSCs). Different interfaces in the PSCs influence the performance remarkably either by altering the crystallization of the active material or shifting the energy levels or improving the electrical contact. This work reports how a thin layer of cesium acetate on the TiO2 electron transport layer (ETL) induces generation of a PbI2-rich methylammonium lead iodide (MAPbI3) composition at the ETL/MAPbI3 interface, which downshifts the conduction band level of MAPbI3 to create an energy level gradient favorable for carrier collection, resulting in higher photocurrent, fill factor, and overall power conversion efficiency.

VOC Over 1.4 V for Amorphous Tin-Oxide-Based Dopant-Free CsPbI2Br Perovskite Solar Cells.

CsPbI2Br perovskite solar cells have attracted much attention because of the rapid development in their efficiency and their great potential as a top cell of tandem solar cells. However, the VOC outputs observed so far in most cases are far from that desired for a top cell. Up to now, with various kinds of treatments, the reported champion VOC is only 1.32 V, with a VOC deficit of 0.60 V. In this work, we found that aging of the SnCl2 precursor solution for the electron-transporting layer can promote the VOC of CsPbI2Br solar cells by employing a dopant-free-polymer hole transport material (HTM) over 1.40 V and efficiency over 15.5% with high reproducibility. With the champion VOC of 1.43 V, the VOC deficit was reduced to <0.50 V, which is achieved for the first time. This simple technique of SnCl2 solution aging forms a uniform and smooth amorphous SnOx film with pure Sn4+, elevates the conduction band of SnOx, and reduces the interfacial gaps and the trap state density of the device, resulting in enhancement in average VOC from ∼1.2 V in the nonaged case to ∼1.4 V in the aged case. Furthermore, the device using an aged SnCl2 solution also exhibits a much better long-term stability than that made of the fresh solution. These achievements in dopant/additive-free CsPbI2Br solar cells can be useful for future research on CsPbI2Br and tandem solar cells.

Full Efficiency Recovery in Hole-Transporting Layer-Free Perovskite Solar Cells With Free-Standing Dry-Carbon Top-Contacts.

Carbon-based top electrodes for hole-transporting-layer-free perovskite solar cells (PSCs) were made by hot press (HP) transfer of a free-standing carbon-aluminum foil at 100°C and at a pressure of 0.1 MPa on a methylammonium lead iodide (MAPbI3) layer. Under these conditions, the perovskite surface was preserved from interaction with the solvent. Over a timescale of 90 days, HP-PSCs were systematically compared to reference cells with carbon-based top electrodes deposited by doctor blading (DB). We found that all the photovoltaic parameters recorded in HP-PSCs during time under ambient conditions settled on values systematically higher than those measured in the reference DB-PSCs, with efficiency stabilized at around 6% within the first few measurements. On the other hand, in DB-PSCs, a long-lasting (~14 days) degrading transient of the performances was observed, with a loss of efficiency from an initial ~8% to ~3%. Moreover, in HP-PSCs, a systematic day-by-day recovery of the efficiency after operation was observed (Δ~2%) by leaving the cell under open circuit, a nitrogen environment, and dark conditions. Noteworthily, a full recovery of all the parameters was observed at the end of the experiment, while DB-PSCs showed only a partial recovery under the same conditions. Hence, the complete release of solvent from the carbon contact, before an interface is established with the perovskite layer, offers a definite advantage through the long period of operation in preventing irreversible degradation. Our findings indeed highlight the crucial role of the interfaces and their feasible preservation under nitrogen atmosphere.

Photomultiplying Visible Light Detection by Halide Perovskite Nanoparticles Hybridized with an Organo Eu Complex.

A molecular layer of an organo europium (Eu) complex was hybridized with the surface of halide perovskite (MAPbI3) nanocrystals to control charge transport between photoexcited perovskites and a metal electrode. A thin hybridized nanocrystalline film was found to cause an efficient photomultiplication reaction based on hole accumulation at photoexcited perovskite nanoparticles and charge tunneling across the Eu complex molecules under application of a low external bias (-0.5 V). A photodetecting device based on the Eu complex and perovskite absorber demonstrated photoinduced current generation at extremely high quantum conversion efficiency of 290 000% for weak monochromatic light (<1 mW cm-2), yielding a power responsivity value up to 1289 A W-1. High sensitivity of photodetection was enabled by using nanosized particles (<5 nm) of perovskite having a high surface area in contact with the Eu complex, while sensitivity was reduced by use of thick and large particle perovskite layers.

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects.

The photovoltaics of organic-inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regarding compositional engineering of the hybrid perovskite structure are discussed, including potentials for developing all-inorganic and lead-free perovskite materials. Looking at the latest cutting-edge research, the prospects for perovskite-based photovoltaic and optoelectronic devices, including non-photovoltaic applications such as X-ray detectors and image sensing devices in industrialization, are described. In addition to the aforementioned major topics, we also review, as a background, our encounter with perovskite materials for the first solar cell application, which should inspire young researchers in chemistry and physics to identify and work on challenging interdisciplinary research problems through exchanges between academia and industry.

Poly(4-Vinylpyridine)-Based Interfacial Passivation to Enhance Voltage and Moisture Stability of Lead Halide Perovskite Solar Cells.

It is well known that the surface trap states and electronic disorders in the solution-processed CH3 NH3 PbI3 perovskite film affect the solar cell performance significantly and moisture sensitivity of photoactive perovskite material limits its practical applications. Herein, we show the surface modification of a perovskite film with a solution-processable hydrophobic polymer (poly(4-vinylpyridine), PVP), which passivates the undercoordinated lead (Pb) atoms (on the surface of perovskite) by its pyridine Lewis base side chains and thereby eliminates surface-trap states and non-radiative recombination. Moreover, it acts as an electron barrier between the perovskite and hole-transport layer (HTL) to reduce interfacial charge recombination, which led to improvement in open-circuit voltage (Voc ) by 120 to 160 mV whereas the standard cell fabricated in same conditions showed Voc as low as 0.9 V owing to dominating interfacial recombination processes. Consequently, the power conversion efficiency (PCE) increased by 3 to 5 % in the polymer-modified devices (PCE=15 %) with Voc more than 1.05 V and hysteresis-less J-V curves. Advantageously, hydrophobicity of the polymer chain was found to protect the perovskite surface from moisture and improved stability of the non-encapsulated cells, which retained their device performance up to 30 days of exposure to open atmosphere (50 % humidity).

A Switchable High-Sensitivity Photodetecting and Photovoltaic Device with Perovskite Absorber.

Amplified photocurrent gain has been obtained by photodiodes of inorganic semiconductors such as GaAs and Si. The avalanche photodiode, developed for high-sensitivity photodetectors, requires an expensive vapor-phase epitaxy manufacture process and high driving voltage (50-150 V). Here, we show that a low-cost solution-processed device using a planar-structured ferroelectric organo-lead triiodide perovskite enables light detection in a large dynamic range of incident power (10(-7)-10(-1) W cm(-2)) by switching with small voltage (-0.9 to +0.5 V). The device achieves significantly high external quantum conversion efficiency (EQE) up to 2.4 × 10(5)% (gain value of 2400) under weak monochromatic light. On a single dual-functional device, incident small power (0.2-100 µW cm(-2)) and medium to large power (>0.1 mW cm(-2)) are captured by reverse bias and forward bias modes, respectively, with linear responsivity of current. For weak light detection, the device works with a high responsivity value up to 620 A W(-1).

The Interface between FTO and the TiO2 Compact Layer Can Be One of the Origins to Hysteresis in Planar Heterojunction Perovskite Solar Cells.

Organometal halide perovskite solar cells have shown rapid rise in power conversion efficiency, and therefore, they have gained enormous attention in the past few years. However, hysteretic photovoltaic characteristics, found in these solid-state devices, have been a major problem. Although it is being proposed that the ferroelectric property of perovskite causes hysteresis in the device, we observed hysteresis in a device made of nonferroelectric PbI2 as a light absorber. This result evidently supports the fact that ferroelectric property cannot be the sole reason for hysteresis. The present study investigates the roles of some key interfaces in a planar heterojunction perovskite (CH3NH3PbI(3-x)Cl(x)) solar cell that can potentially cause hysteresis. The results confirm that the interface between fluorine doped tin oxide (FTO) substrate and the TiO2 compact layer has a definite contribution to hysteresis. Although this interface is one of the origins to hysteresis, we think that other interfaces, especially the interface of the TiO2 compact layer with perovskite, can also play major roles. Nevertheless, the results indicate that hysteresis in such devices can be reduced/eliminated by changing the interlayer between FTO and perovskite.