Stability and Dark Hysteresis Correlate in NiO-Based Perovskite Solar Cells

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim In perovskite solar cells (PSCs), the interfaces are a weak link with respect to degradation. Electrochemical reactivity of the perovskite's halides has been reported for both molecular and polymeric hole selective layers (HSLs), and here it is shown that also NiO brings about this decomposition mechanism. Employing NiO as an HSL in p–i–n PSCs with power conversion efficiency (PCE) of 16.8%, noncapacitive hysteresis is found in the dark, which is attributable to the bias-induced degradation of perovskite/NiO interface. The possibility of electrochemically decoupling NiO from the perovskite via the introduction of a buffer layer is explored. Employing a hybrid magnesium-organic interlayer, the noncapacitive hysteresis is entirely suppressed and the device's electrical stability is improved. At the same time, the PCE is improved up to 18% thanks to reduced interfacial charge recombination, which enables more efficient hole collection resulting in higher Voc and FF

Aerosol Assisted Solvent Treatment: A Universal Method for Performance and Stability Enhancements in Perovskite Solar Cells

Abstract: Metal‐halide perovskite solar cells (PSCs) have had a transformative impact on the renewable energy landscape since they were first demonstrated just over a decade ago. Outstanding improvements in performance have been demonstrated through structural, compositional, and morphological control of devices, with commercialization now being a reality. Here the authors present an aerosol assisted solvent treatment as a universal method to obtain performance and stability enhancements in PSCs, demonstrating their methodology as a convenient, scalable, and reproducible post‐deposition treatment for PSCs. Their results identify improvements in crystallinity and grain size, accompanied by a narrowing in grain size distribution as the underlying physical changes that drive reductions of electronic and ionic defects. These changes lead to prolonged charge‐carrier lifetimes and ultimately increased device efficiencies. The versatility of the process is demonstrated for PSCs with thick (>1 µm) active layers, large‐areas (>1 cm2) and a variety of device architectures and active layer compositions. This simple post‐deposition process is widely transferable across the field of perovskites, thereby improving the future design principles of these materials to develop large‐area, stable, and efficient PSCs

Ss-Sl2, a Novel Cell Wall Protein with PAN Modules, Is Essential for Sclerotial Development and Cellular Integrity of Sclerotinia sclerotiorum

The sclerotium is an important dormant body for many plant fungal pathogens. Here, we reported that a protein, named Ss-Sl2, is involved in sclerotial development of Sclerotinia sclerotiorum. Ss-Sl2 does not show significant homology with any protein of known function. Ss-Sl2 contains two putative PAN modules which were found in other proteins with diverse adhesion functions. Ss-Sl2 is a secreted protein, during the initial stage of sclerotial development, copious amounts of Ss-Sl2 are secreted and accumulated on the cell walls. The ability to maintain the cellular integrity of RNAi-mediated Ss-Sl2 silenced strains was reduced, but the hyphal growth and virulence of Ss-Sl2 silenced strains were not significantly different from the wild strain. Ss-Sl2 silenced strains could form interwoven hyphal masses at the initial stage of sclerotial development, but the interwoven hyphae could not consolidate and melanize. Hyphae in these interwoven bodies were thin-walled, and arranged loosely. Co-immunoprecipitation and yeast two-hybrid experiments showed that glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Woronin body major protein (Hex1) and elongation factor 1-alpha interact with Ss-Sl2. GAPDH-knockdown strains showed a similar phenotype in sclerotial development as Ss-Sl2 silenced strains. Hex1-knockdown strains showed similar impairment in maintenance of hyphal integrity as Ss-Sl2 silenced strains. The results suggested that Ss-Sl2 functions in both sclerotial development and cellular integrity of S. sclerotiorum

Characterising degradation of perovskite solar cells through in-situ and operando electron microscopy

Organic-inorganic hybrid perovskite solar cells have exhibited power conversion efficiencies comparable to more established PV technologies thanks to their favourable optoelectronic properties, but low operational stability inhibits their commercialisation and widespread use. Many degradation pathways are possible and most of them are not currently well understood at the nanoscale due to the difficulty of characterising a perovskite solar cell’s complex nanostructure. This work reviews the application of in-situ and operando electron microscopy to visualise the dynamic processes that occur in perovskite solar cells as various stimuli are applied inside a microscope column. Additionally, potential challenges and an outlook on future uses of this technique are briefly discussed

Self-Assembly of rGO Coated Nanorods into Aligned Thick Films

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Self-assembly is a very effective and popular method to create monolayers or thin films of aligned nanorods and ellipsoids. Nevertheless, there has been little attention to forming thick films of aligned nanorods using this approach. Here, the self-assembly mechanism of nanorods coated with reduced graphene oxide in thick films with both a surface and a bulk alignment process is underpinned. The alignment method is robust and results in films with up to 50% higher volumetric density compared to nonaligned films of the same material. To optimize the coating process, an image processing script is implemented that quantifies the quality of the alignment based on a fast Fourier transform of nanorod electron microscope images. Based on this analysis, parameters are identified that influence the alignment to optimize the process for obtaining large area domains. Finally, dip-coating, blade casting and zone coating are tested and compared and lithographically patterned substrates are used to template the self-assembly process

Self-Assembly of rGO Coated Nanorods into Aligned Thick Films

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Self-assembly is a very effective and popular method to create monolayers or thin films of aligned nanorods and ellipsoids. Nevertheless, there has been little attention to forming thick films of aligned nanorods using this approach. Here, the self-assembly mechanism of nanorods coated with reduced graphene oxide in thick films with both a surface and a bulk alignment process is underpinned. The alignment method is robust and results in films with up to 50% higher volumetric density compared to nonaligned films of the same material. To optimize the coating process, an image processing script is implemented that quantifies the quality of the alignment based on a fast Fourier transform of nanorod electron microscope images. Based on this analysis, parameters are identified that influence the alignment to optimize the process for obtaining large area domains. Finally, dip-coating, blade casting and zone coating are tested and compared and lithographically patterned substrates are used to template the self-assembly process

Fabrication and Morphological Characterization of High-Efficiency Blade-Coated Perovskite Solar Modules

Organo-metal halide perovskite demonstrates a large potential for achieving highly efficient photovoltaic devices. The scaling-up process represents one of the major challenges to exploit this technology at the industrial level. Here, the scaling-up of perovskite solar modules from 5 x 5 to 10 x 10 cm(2) substrate area is reported by blade coating both the CH3NH3PbI3 perovskite and spiro-OMeTAD layers. The sequential deposition approach is used in which both lead iodide (PbI2) deposition and the conversion step are optimized by using additives. The PbI2 solution is modified by adding methylammonium iodide (MAI) which improves perovskite crystallinity and pore filling of the mesoporous TiO2 scaffold. Optimization of the conversion step is achieved by adding a small concentration of water into the MAI-based solution, producing large cubic CH3NH3PbI3 grains. The combination of the two modifications leads to a power conversion efficiency of 14.7% on a perovskite solar module with an active area of 47 cm(2)

Improved Electrical Performance of Perovskite Photovoltaic Mini-Modules through Controlled PbI<inf>2</inf> Formation Using Nanosecond Laser Pulses for P3 Patterning

The upscaling of perovskite solar cells to modules requires the patterning of the layer stack in individual cells that are monolithically interconnected in series. This interconnection scheme is composed of three lines, P1–P3, which are scribed using a pulsed laser beam. The P3 scribe is intended to isolate the back contact layer of neighboring cells, but is often affected by undesired effects such as back contact delamination, flaking, and poor electrical isolation. Herein, the influence of the laser pulse duration on the electrical and compositional properties of P3 scribe lines is investigated. The results show that both nanosecond and picosecond laser pulses are suitable for P3 patterning, with the nanosecond pulses leading to a higher open circuit voltage, a higher fill factor, and a higher power conversion efficiency. It is found that the longer pulse duration resultes in a larger amount of PbI2 formed within the P3 line and a thin Br‐rich interfacial layer which both effectively passivate defects at the scribe line edges and block charge carrier in its vicinity. Thus, nanosecond laser pulses are preferable for P3 patterning as they promote the formation of beneficial chemical phases, resulting in an improved photovoltaic performance.</jats:sec

Evaluation of cassava peel waste as lowcost biosorbent for Ni-sorption : equilibrium, kinetics, thermodynamics and mechanism

The feasibility of cassava peel waste for Ni-sorption is evaluated in this work. The biosorbents are characterized by Boehm titration, Fourier transform-infra red (FTIR) spectroscopy, Nitrogen sorption, scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis (e.g. elemental mapping) and X-ray photoelectron spectroscopy (XPS). Adsorption experiments are performed in batch mode at 30 &deg;C (303.15 K), 45 &deg;C (318.15 K) and 60 &deg;C (333.15 K). The performance of several temperature dependence forms of isotherm models e.g. Langmuir, Freundlich, Sips and Toth to represent the adsorption equilibrium data is evaluated and contrasted. Sips model demonstrates the best fitting with the maximum uptake capacity for Ni(II) ions of 57 mg/g (0.971 mmol/g) at pH 4.5. For kinetic data correlation, pseudo-second order model shows the best representation. The chemisorption mechanism and thermodynamics aspect are also discussed.<br /