The Role of Luminescent Coupling in Monolithic Perovskite/Silicon Tandem Solar Cells.

Luminescent coupling (LC) is a key phenomenon in monolithic tandem solar cells. This study presents a nondestructive technique to quantitatively evaluate the LC effect, addressing a gap in the existing predictions made by optical modeling. The method involves measuring the ratio of photons emitted from the high bandgap top cell that escape through the rear, contributing additional current to the bottom cell, and to those escaping from the front side of top cell.

Centimetre-scale perovskite solar cells with fill factors of more than 86 per cent.

Owing to rapid development in their efficiency and stability, perovskite solar cells are at the forefront of emerging photovoltaic technologies. State-of-the-art cells exhibit voltage losses approaching the theoretical minimum and near-unity internal quantum efficiency, but conversion efficiencies are limited by the fill factor (<83%, below the Shockley-Queisser limit of approximately 90%). This limitation results from non-ideal charge transport between the perovskite absorber and the cell's electrodes.

Large-scale stationary hydrogen storage via liquid organic hydrogen carriers.

Large-scale stationary hydrogen storage is critical if hydrogen is to fulfill its promise as a global energy carrier. While densified storage via compressed gas and liquid hydrogen is currently the dominant approach, liquid organic molecules have emerged as a favorable storage medium because of their desirable properties, such as low cost and compatibility with existing fuel transport infrastructure. This perspective article analytically investigates hydrogenation systems' technical and economic prospects using liquid organic hydrogen carriers (LOHCs) to store hydrogen at a large scale compared to densified storage technologies and circular hydrogen carriers (mainly ammonia and methanol).

Hole-Storage Enhanced a-Si Photocathodes for Efficient Hydrogen Production.

Ferrihydrite (Fh) has been demonstrated as an effective interfacial layer for photoanodes to achieve outstanding photoelectrochemical (PEC) performance for water oxidation reaction owing to its unique hole-storage function. However, it is unknown whether such a hole-storage layer can be used to construct highly efficient photocathodes for hydrogen evolution reaction (HER). In this work, we report Fh interfacial engineering of amorphous silicon photocathode (with nickel as HER cocatalyst) achieving a photocurrent density of 15.

Nanoscale localized contacts for high fill factors in polymer-passivated perovskite solar cells.

Polymer passivation layers can improve the open-circuit voltage of perovskite solar cells when inserted at the perovskite-charge transport layer interfaces. Unfortunately, many such layers are poor conductors, leading to a trade-off between passivation quality (voltage) and series resistance (fill factor, FF). Here, we introduce a nanopatterned electron transport layer that overcomes this trade-off by modifying the spatial distribution of the passivation layer to form nanoscale localized charge transport pathways through an otherwise passivated interface, thereby providing both effective passivation and excellent charge extraction.

In Situ Formation of Mixed-Dimensional Surface Passivation Layers in Perovskite Solar Cells with Dual-Isomer Alkylammonium Cations.

Dimensional engineering of perovskite solar cells has attracted significant research attention recently because of the potential to improve both device performance and stability. Here, a novel 2D passivation scheme for 3D perovskite solar cells is demonstrated using a mixed cation composition of 2D perovskite based on two different isomers of butylammonium iodide. The dual-cation 2D perovskite outperforms its single cation 2D counterparts in surface passivation quality, resulting in devices with an impressive open-circuit voltage of 1.

Light-activated inorganic CsPbBrI perovskite for room-temperature self-powered chemical sensing.

Halide perovskite materials are excellent light harvesters that have generated enormous interest for photovoltaic technology and an increasing number of other optoelectronic applications. Very recently, their use for miniaturized chemical sensors has shown a promising room-temperature response. Here, we present some insights on the use of CsPbBr2I (CPBI) perovskites for self-powered room-temperature sensing of several environmentally and medically relevant compounds demonstrating rapid detection of down to concentrations of 1 ppm.

Light Management: A Key Concept in High-Efficiency Perovskite/Silicon Tandem Photovoltaics.

The remarkable recent progress in perovskite photovoltaics affords a novel opportunity to advance the power conversion efficiency of market-dominating crystalline silicon (c-Si) solar cells. A severe limiting factor in the development of perovskite/c-Si tandems to date has been their inferior light-harvesting ability compared to single-junction c-Si solar cells, but recent innovations have made impressive headway on this front. Here, we provide a quantitative perspective on future steps to advance perovskite/c-Si tandem photovoltaics from a light-management point of view, addressing key challenges and available strategies relevant to both the 2-terminal and 4-terminal perovskite/c-Si tandem architectures.

In situ recombination junction between p-Si and TiO enables high-efficiency monolithic perovskite/Si tandem cells.

Increasing the power conversion efficiency of silicon (Si) photovoltaics is a key enabler for continued reductions in the cost of solar electricity. Here, we describe a two-terminal perovskite/Si tandem design that increases the Si cell's output in the simplest possible manner: by placing a perovskite cell directly on top of the Si bottom cell. The advantageous omission of a conventional interlayer eliminates both optical losses and processing steps and is enabled by the low contact resistivity attainable between n-type TiO and Si, established here using atomic layer deposition.

Perovskite Photovoltaic Integrated CdS/TiO Photoanode for Unbiased Photoelectrochemical Hydrogen Generation.

Photoelectrolysis of water using solar energy into storable and environment-friendly chemical fuel in the form of hydrogen provides a potential solution to address the environmental concerns and fulfill future energy requirements in a sustainable manner. Achieving efficient and spontaneous hydrogen evolution in water using solar light as the only energy input is a highly desirable but a difficult target. In this work, we report perovskite solar cell integrated CdS-based photoanode for unbiased photoelectrochemical hydrogen evolution.

Superior Self-Powered Room-Temperature Chemical Sensing with Light-Activated Inorganic Halides Perovskites.

Hybrid halide perovskite is one of the promising light absorber and is intensively investigated for many optoelectronic applications. Here, the first prototype of a self-powered inorganic halides perovskite for chemical gas sensing at room temperature under visible-light irradiation is presented. These devices consist of porous network of CsPbBr (CPB) and can generate an open-circuit voltage of 0.

Light and Electrically Induced Phase Segregation and Its Impact on the Stability of Quadruple Cation High Bandgap Perovskite Solar Cells.

Perovskite material with a bandgap of 1.7-1.8 eV is highly desirable for the top cell in a tandem configuration with a lower bandgap bottom cell, such as a silicon cell.

Inverted Hysteresis in CHNHPbI Solar Cells: Role of Stoichiometry and Band Alignment.

J-V hysteresis in perovskite solar cells is known to be strongly dependent on many factors ranging from the cell structure to the preparation methods. Here we uncover one likely reason for such sensitivity by linking the stoichiometry in pure CHNHPbI (MAPbI) perovskite cells with the character of their hysteresis behavior through the influence of internal band offsets. We present evidence indicating that in some cells the ion accumulation occurring at large forward biases causes a temporary and localized increase in recombination at the MAPbI/TiO interface, leading to inverted hysteresis at fast scan rates.

Improved Reproducibility for Perovskite Solar Cells with 1 cm Active Area by a Modified Two-Step Process.

With rapid progress in recent years, organohalide perovskite solar cells (PSC) are promising candidates for a new generation of highly efficient thin-film photovoltaic technologies, for which up-scaling is an essential step toward commercialization. In this work, we propose a modified two-step method to deposit the CHNHPbI (MAPbI) perovskite film that improves the uniformity, photovoltaic performance, and repeatability of large-area perovskite solar cells. This method is based on the commonly used two-step method, with one additional process involving treating the perovskite film with concentrated methylammonium iodide (MAI) solution.

Hysteresis phenomena in perovskite solar cells: the many and varied effects of ionic accumulation.

The issue of hysteresis in perovskite solar cells has now been convincingly linked to the presence of mobile ions within the perovskite layer. Here we test the limits of the ionic theory by attempting to account for a number of exotic characterization results using a detailed numerical device model that incorporates ionic charge accumulation at the perovskite interfaces. Our experimental observations include a temporary enhancement in open-circuit voltage following prolonged periods of negative bias, dramatically S-shaped current-voltage sweeps, decreased current extraction following positive biasing or "inverted hysteresis", and non-monotonic transient behaviours in the dark and the light.

Flame-made ultra-porous TiO layers for perovskite solar cells.

We report methyl ammonium lead iodide (MAPbI) solar cells with an ultra-porous TiO electron transport layer fabricated using sequential flame aerosol and atomic layer depositions of porous and compact TiO layers. Flame aerosol pyrolysis allows rapid deposition of nanostructured and ultra-porous TiO layers that could be easily scaled-up for high-throughput low-cost industrial solar cell production. An efficiency of 13.

Photoluminescence study of time- and spatial-dependent light induced trap de-activation in CH3NH3PbI3 perovskite films.

Organometal halide perovskite-based solar cells have rapidly achieved high efficiency in recent years. However, many fundamental recombination mechanisms underlying the excellent performance are still not well understood. Here we apply confocal photoluminescence microscopy to investigate the time and spatial characteristics of light-induced trap de-activation in CH3NH3PbI3 perovskite films.

Ultralow Absorption Coefficient and Temperature Dependence of Radiative Recombination of CH3NH3PbI3 Perovskite from Photoluminescence.

Spectrally resolved photoluminescence is used to measure the band-to-band absorption coefficient α(BB)(ℏω) of organic-inorganic hybrid perovskite methylammonium lead iodide (CH₃NH₃PbI₃) films from 675 to 1400 nm. Unlike other methods used to extract the absorption coefficient, photoluminescence is only affected by band-to-band absorption and is capable of detecting absorption events at very low energy levels. Absorption coefficients as low as 10⁻¹⁴ cm⁻¹ are detected at room temperature for long wavelengths, which is 14 orders of magnitude lower than reported values at shorter wavelengths.

Light trapping efficiency comparison of Si solar cell textures using spectral photoluminescence.

The band-to-band absorption enhancement due to various types of light trapping structures is studied experimentally with photoluminescence (PL) on monocrystalline silicon wafers. Four basic light trapping structures are examined: reactive ion etched texture (RIE), metal-assisted etched texture (MET), random pyramid texture (RAN) and plasmonic Ag nanoparticles with a diffusive reflector (Ag/DR). We also compare two novel combined structures of front side RIE/rear side RAN and front side RIE/rear side Ag/DR.

Three-dimensional nanotub submicrometer diffraction gratings for solar cells.

Diffraction gratings are a promising approach for reducing reflection and achieving light-trapping in solar cells. Using square lattices as a base structure, we investigate a novel bi-periodic nanotub three-dimensional grating structure and compare it with established textured structures for thin-film and wafer applications. For wafer application, simulations show that optimal AR coated nanotubs demonstrated solar weighted reflectance (SWR) of 2% compared to AR coated square pyramids with values 1.

Enhanced light trapping in solar cells using .

A novel method, , is found to show significant enhancement of the short circuit current (35%) when applied as a scattering back reflector for polycrystalline silicon thin-film solar cells. The coating is formed from high refractive index titania particles without containing binder and gives close to 100% reflectance for wavelengths above 400 nm. Snow globe coating is a physicochemical coating method executable in pH neutral media.

Light trapping with plasmonic particles: beyond the dipole model.

Disk-shaped metal nanoparticles on high-index substrates can support resonant surface plasmon polariton (SPP) modes at the interface between the particle and the substrate. We demonstrate that this new conceptual model of nanoparticle scattering allows clear predictive abilities, beyond the dipole model. As would be expected from the nature of the mode, the SPP resonance is very sensitive to the area in contact with the substrate, and insensitive to particle height.

Nanostructures in photovoltaics.

The world has recently been waking up to the urgent need to move away from fossil fuels and towards a low-carbon economy. To achieve this, we need a way of producing electricity that is efficient, widely applicable and cheap. At the same time, there has recently been an appreciation of the tremendous scope for making entirely new types of devices, and even seeing new physics, by structuring matter at the nanoscale.