ZiQi Sun

In this work, for the first time, the diameter limit of surfactant wrapped single walled carbon nanotubes (SWCNTs) in SWCNT:C₆₀ solar cells is determined through preparation of monochiral small and large diameter nanotube devices as well as those from polychiral mixtures. Through assignment of the different nanotube chiralities by photoluminescence and optical density measurements a diameter limit yielding 0% internal quantum efficiency (IQE) is determined. This work provides insights into the required net driving energy for SWCNT exciton dissociation onto C₆₀ and establishes a family of (n,m) species which can efficiently be utilized in polymer-free SWCNT:C₆₀ solar cells. Using this approach the largest diameter nanotube with an IQE > 0% is found to be (8,6) with a diameter of 0.95 nm. Possible strategies to extend this diameter limit are then discussed.

Distribution of various (n,m) species that have an internal quantum efficiency (IQE) greater (green) than or equal (grey) to zero, based on their diameter. Depending on their diameter, excitons may or may not be dissociated at the interface of surfactant wrapped single walled carbon nanotubes and C₆₀.

Solution-processed few-layer MoS₂ flakes are exploited as an active buffer layer in hybrid lead–halide perovskite solar cells (PSCs). Glass/FTO/compact-TiO₂/mesoporous-TiO₂/CH₃NH₃PbI₃/MoS₂/Spiro-OMeTAD/Au solar cells are realized with the MoS₂ flakes having a twofold function, acting both as a protective layer, by preventing the formation of shunt contacts between the perovskite and the Au electrode, and as a hole transport layer from the perovskite to the Spiro-OMeTAD. As prepared PSC demonstrates a power conversion efficiency (η) of 13.3%, along with a higher lifetime stability over 550 h with respect to reference PSC without MoS₂ (Δη/η = −7% vs. Δη/η = −34%). Large-area PSCs (1.05 cm² active area) are also fabricated to demonstrate the scalability of this approach, achieving η of 11.5%. Our results pave the way toward the implementation of MoS₂ as a material able to boost the shelf life of large-area perovskite solar cells in view of their commercialization.

MoS₂ flakes are proposed as an active buffer layer in hybrid lead halide perovskite solar cells. By preventing the formation of shunt contacts between the perovskite and the metal electrode, MoS₂ flakes act as a protective layer to increase the cell stability, while also easing the hole collection at the anode. Such approach leads to efficient and stable perovskite solar cells.

Semitransparent perovskite solar cells based on smooth perovskite films and ultrathin Cu (1 nm)/Au (7 nm) metal electrode demonstrate an efficiency of 16.5%. When illuminated through the semitransparent perovskite cell, a near-infrared-enhanced silicon heterojunction solar cell operates with 6.5% efficiency, leading to a total perovskite/silicon four-terminal tandem efficiency of 23.0%.

Molecular hydrogen can be generated renewably by water splitting with an “artificial-leaf device”, which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate efficiently and be fabricated with cost-efficient means using earth-abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface-area NiCo₂O₄ nanorods that are firmly anchored onto a carbon–paper current collector via a dense network of nitrogen-doped carbon nanotubes is presented. This electrocatalyst electrode is bifunctional in that it can efficiently operate as both anode and cathode in the same alkaline solution, as quantified by a delivered current density of 10 mA cm⁻² at an overpotential of 400 mV for each of the oxygen and hydrogen evolution reactions. By driving two such identical electrodes with a solution-processed thin-film perovskite photovoltaic assembly, a wired artificial-leaf device is obtained that features a Faradaic H₂ evolution efficiency of 100%, and a solar-to-hydrogen conversion efficiency of 6.2%. A detailed cost analysis is presented, which implies that the material-payback time of this device is of the order of 100 days.

An artificial-leaf device is constructed by driving two carbon-based, bifunctional, and lightweight catalyst electrodes immersed in water with an assembly of solution-processed perovskite photovoltaics. The device delivers hydrogen gas at 100% Faradaic efficiency and with a solar-to-hydrogen efficiency of 6.2%, and a cost analysis suggests that the material-payback time can be of the order of 100 days.

During the past few years, the field of photovoltaics has been revolutioned through the use of perovskites as light-harvesting materials. This has led to studying a whole range of organic structures fulfilling the energetical requirements within the typical architecture of a perovskite-based solar cell. In this context, carbon nanoforms, with their interesting and versatile properties, are studied as charge transporting materials, electrodes or as additives within the light-harvesting perovskite material. The latest findings concerning the exciting field of carbon nanostructures for PSCs are summarized.

Carbon nanoforms, owing to their interesting and versatile properties, are studied as charge transporting materials, electrodes or as additives within the revolutionary field of perovskite-based solar cells. The latest findings concerning the exciting field of carbon nanostructures for PSCs are summarized.

In article number 1600386, Jeffrey G. Tait and co-workers develop non-hazardous ink systems, based on solvent-alcohol-acid, for coating perovskite photovoltaic films in a single step. Coating was further developed from spin to blade, while the high yield process produced efficient 4 cm² modules.

Poly(Phenylene vinylene) anionic polyelectrolyte (PVBT-SO₃) was found to be an efficient hole extraction layer for inverted perovskite solar cells. It can be cast from an aqueous solution and does not require thermal annealing for improved device performance. The devices show maximum solar cell efficiency of 15.9% and exhibit improved stability under ambient conditions and enhanced charge extraction.

A low-cost carbon cloth is applied in perovskite solar cells (PSC) as a collector composite and degradation inhibitor. This study incorporates carbon fibers as a back contact in perovskite solar cells, which results in enhancement in all photovoltaic parameters. This material is suitable for large-scale fabrication of PSCs as it has shown an improved long-term stability when compared to the gold counterpart under elevated temperatures.

Ionic liquids can retard the perovskite crystallization with the aim to form compact films with larger and more uniformly distributed grain size. The ionic liquid driven crystallization is exploited to prepared a record planar perovskite solar cell with stabilized power output of 19.5%.

Precisely controlling the optimal amount of hydration water in the precursor solution, results in the formation of a smooth and uniform perovskite film, as described by Y. Zhan, L. Zheng, and co-workers on page 5028. With appropriate annealing, the perovskite monohydrate loses its hydration water and crystallizes into pristine MAPbI₃. The simplicity of controlling hydration water during precursor solution preparation will influence mass production of perovskite solar cells.

Highly efficient electron extraction is achieved by using a photoconductive cathode interlayer in inverted ternary organic solar cells (OSCs) where a near-IR absorbing porphyrin molecule is used as the sensitizer. The OSCs show improved device performance when the ratio of the two donors varies in a large region and a maximum power conversion efficiency up to 11.03% is demonstrated.

The family of solution-processed tin-based perovskites is demonstrated as a new and superior near-infrared gain medium. Due to the large electron–hole bimolecular recombination associated with tin and the reduced trap density with SnF₂ treatment, these lead-free “green” perovskites yield stable coherent light emission extending to ≈1 μm at strikingly low thresholds.

Uniform perovskite films are achieved by HCl-assisted one-step spin-coating at room temperature. By this method, a highest power conversion efficiency of 17.9% is obtained for perovskite solar cells (PSCs). The devices retain ≈95% of their original efficiency after storage in air for two months. The highest efficiency obtained for large-area PSCs (0.86 cm²) is 15.7%.

A synapse-emulating electronic device based on organometal halide perovskite thin films is described by T.-W. Lee and co-workers on page 5916. The device successfully emulates important characteristics of a biological synapse. This work extends the application of organometal halide perovskites to bioinspired electronic devices, and contributes to the development of neuromorphic electronics.