Hanlin Hu

Bio: Hanlin Hu is an academic researcher from Shenzhen Polytechnic. The author has contributed to research in topics: Materials science & Perovskite (structure). The author has an hindex of 20, co-authored 39 publications receiving 1406 citations. Previous affiliations of Hanlin Hu include Tianjin University of Science and Technology & Shenzhen University.

Stable High-Performance Perovskite Solar Cells via Grain Boundary Passivation.

Abstract: The trap states at grain boundaries (GBs) within polycrystalline perovskite films deteriorate their optoelectronic properties, making GB engineering particularly important for stable high-performance optoelectronic devices. It is demonstrated that trap states within bulk films can be effectively passivated by semiconducting molecules with Lewis acid or base functional groups. The perovskite crystallization kinetics are studied using in situ synchrotron-based grazing-incidence X-ray scattering to explore the film formation mechanism. A model of the passivation mechanism is proposed to understand how the molecules simultaneously passivate the Pb-I antisite defects and vacancies created by under-coordinated Pb atoms. In addition, it also explains how the energy offset between the semiconducting molecules and the perovskite influences trap states and intergrain carrier transport. The superior optoelectronic properties are attained by optimizing the molecular passivation treatments. These benefits are translated into significant enhancements of the power conversion efficiencies to 19.3%, as well as improved environmental and thermal stability of solar cells. The passivated devices without encapsulation degrade only by ≈13% after 40 d of exposure in 50% relative humidity at room temperature, and only ≈10% after 24 h at 80 °C in controlled environment.

Hybrid Perovskite Thin‐Film Photovoltaics: In Situ Diagnostics and Importance of the Precursor Solvate Phases

Abstract: Solution-processed hybrid perovskite semiconductors attract a great deal of attention, but little is known about their formation process. The one-step spin-coating process of perovskites is investigated in situ, revealing that thin-film formation is mediated by solid-state precursor solvates and their nature. The stability of these intermediate phases directly impacts the quality and reproducibility of thermally converted perovskite films and their photovoltaic performance.

Recent progress in morphology optimization in perovskite solar cell

Abstract: Hybrid organic–inorganic halide perovskite based solar cell technology has passed through a phase of unprecedented growth in the efficiency scale from 3.8% to above 25% within a decade. This technology has drawn tremendous research interest because of facile solution processability, ease of large scale manufacturing and ultra-low cost production of perovskite based thin film solar cells. It has been observed that performances of perovskite-based solar cells are extremely dependent on the morphology and crystallinity of the perovskite layer. The high-quality perovskite films have made a significant impact on the fabrication of efficient and stable hybrid perovskite solar cells. It has also been observed that device lifetime depends on the perovskite morphology; devices with larger perovskite grains degrade slowly than those of the smaller ones. Various methods of perovskite growth such as sequential deposition, doctor blading, slot die coating and spray coating have been applied to achieve the most appropriate morphology necessary for highly efficient and stable solar cells. This review focuses on the recent progress in morphology optimizations by various processing condition such as annealing condition, additive effects, Lewis acid–base adduct approach, precursor solution aging and post-device ligand treatment emphasizing on grain sizes, film uniformity, defect passivation, ambient compatibility and device efficiency and stability. In this review, we also discussed recently developed bifacial stamping technique and deposition methods for large-area and roll-to-roll fabrication of highly efficient and stable perovskite solar cells.

Vertical Phase Separation in Small Molecule:Polymer Blend Organic Thin Film Transistors Can Be Dynamically Controlled

Abstract: Blending of small-molecule organic semiconductors (OSCs) with amorphous polymers is known to yield high performance organic thin film transistors (OTFTs). Vertical stratification of the OSC and polymer binder into well-defined layers is crucial in such systems and their vertical order determines whether the coating is compatible with a top and/or a bottom gate OTFT configuration. Here, we investigate the formation of blends prepared via spin-coating in conditions which yield bilayer and trilayer stratifications. We use a combination of in situ experimental and computational tools to study the competing effects of formulation thermodynamics and process kinetics in mediating the final vertical stratification. It is shown that trilayer stratification (OSC/polymer/OSC) is the thermodynamically favored configuration and that formation of the buried OSC layer can be kinetically inhibited in certain conditions of spin-coating, resulting in a bilayer stack instead. The analysis reveals here that preferential loss of the OSC, combined with early aggregation of the polymer phase due to rapid drying, inhibit the formation of the buried OSC layer. The fluid dynamics and drying kinetics are then moderated during spin-coating to promote trilayer stratification with a high quality buried OSC layer which yields unusually high mobility >2 cm2 V−1 s−1 in the bottom-gate top-contact configuration.

High-Efficiency Perovskite Solar Cells.

Abstract: With rapid progress in a power conversion efficiency (PCE) to reach 25%, metal halide perovskite-based solar cells became a game-changer in a photovoltaic performance race. Triggered by the development of the solid-state perovskite solar cell in 2012, intense follow-up research works on structure design, materials chemistry, process engineering, and device physics have contributed to the revolutionary evolution of the solid-state perovskite solar cell to be a strong candidate for a next-generation solar energy harvester. The high efficiency in combination with the low cost of materials and processes are the selling points of this cell over commercial silicon or other organic and inorganic solar cells. The characteristic features of perovskite materials may enable further advancement of the PCE beyond those afforded by the silicon solar cells, toward the Shockley-Queisser limit. This review summarizes the fundamentals behind the optoelectronic properties of perovskite materials, as well as the important approaches to fabricating high-efficiency perovskite solar cells. Furthermore, possible next-generation strategies for enhancing the PCE over the Shockley-Queisser limit are discussed.

Constructive molecular configurations for surface-defect passivation of perovskite photovoltaics

Abstract: Surface trap–mediated nonradiative charge recombination is a major limit to achieving high-efficiency metal-halide perovskite photovoltaics. The ionic character of perovskite lattice has enabled molecular defect passivation approaches through interaction between functional groups and defects. However, a lack of in-depth understanding of how the molecular configuration influences the passivation effectiveness is a challenge to rational molecule design. Here, the chemical environment of a functional group that is activated for defect passivation was systematically investigated with theophylline, caffeine, and theobromine. When N-H and C=O were in an optimal configuration in the molecule, hydrogen-bond formation between N-H and I (iodine) assisted the primary C=O binding with the antisite Pb (lead) defect to maximize surface-defect binding. A stabilized power conversion efficiency of 22.6% of photovoltaic device was demonstrated with theophylline treatment.