Stability

An international collaboration that includes researchers from China, Switzerland and Saudi Arabia, made progress in the field of perovskite ultra-high-definition (UHD) display technology.  

In order to crack the problem of phase instability in pure red CsPbI₃ perovskite quantum dots in perovskite UHD display technology, the team examined the strategy of “stress manipulation of epitaxial heterojunction interface”. For the first time, the team used the total solution method to realize large-area in-situ controllable preparation of perovskite vdW epitaxial heterojunctions. This discovery yielded, according to the team, a 'breakthrough in material stability and device performance'. It resulted in a high-efficiency, stable pure red perovskite electroluminescent device (LED). Thus, it provides key technical support for the development of next-generation UHD technology.

A research team from East China University of Science and Technology has unveiled a novel method to extend the lifespan of perovskite solar cells by developing an ultrathin protective layer for perovskite materials using graphene and a special transparent polymer. Experiments showed this "armor" doubles materials' stress resistance, reducing the expansion rate to 0.08 percent from 0.31 percent.

Perovskite materials expand by over 1 percent when exposed to light, the team noted, adding that they repeatedly expand and contract under sunlight, like an inflating and deflating balloon, causing the internal crystals to squeeze each other and generate destructive forces, ultimately leading to structural failure. Cells protected by the team's new "armor" maintained 97% efficiency after 3,670 hours, or about 153 days, of continuous operation under simulated real-world conditions of intense light and high temperatures, marking the longest-ever stable operation period for perovskite cells and providing feasibility for commercial use.

Researchers from University of Electronic Science and Technology of China (UESTC), CNRS, Guangzhou University and China Jiliang University have developed a slot-die coating strategy based on pyrrodiazole (PZ) additives in the perovskite precursor solution to simultaneously immobilize lead iodide and formamidinium iodide. 

Image from: Nature Communications

This approach is meant to enhance wet film stability by suppressing colloidal aggregation, retards the crystal growth process, and ensures a consistent growth rate across the films. These effects can promote the formation of large, monolithic grains, enabling large-area perovskite films with homogeneous structure, excellent uniformity, and low defect density under ambient conditions. Using this strategy, the scientists achieved 10 cm × 10 cm inverted perovskite solar modules with a certified efficiency of 20.3% and retained 94% of initial efficiency after 1,000 h in standard testing, along with good working stability and excellent application demonstration, showcasing its great potential for industrialization.

Researchers from the University of Surrey, the National Physical Laboratory and the University of Sheffield have embedded Al₂O₃ nanoparticles, which successfully trapped iodine, to improve the durability of perovskite solar cells (PSCs).

Device architecture of the PSCs used in this study (left) and a photograph of a device (right). Image from: Royal Society of Chemistry

Experiments conducted in extremely hot and humid conditions shown a tenfold increase in performance, lasting more than 1,530 hours as opposed to 160 hours without the alteration. According to the team, by increasing electrical conductivity, decreasing flaws, improving the homogeneity of the perovskite structure, and adding a moisture-resistant layer, the nanoparticles could open the door for more robust and reasonably priced solar technology.

Researchers at the Hong Kong University of Science and Technology (HKUST), University of Tennessee, Oak Ridge National Laboratory, Hong Kong Baptist University and Yale University have taken the lead in breaking through studies of the nanoscale properties of perovskite solar cells (PSCs). This initiative has resulted in the development of more efficient and durable cells, poised to substantially diminish costs and broaden applications, thereby connecting scientific research with the needs of the business community.

The team named the inhomogeneous distribution of cations in perovskite thin films, which can trigger an unfavored phase transition that gradually degrades the devices, as a key factor in causing PSCs' instability. The research team, led by Prof. ZHOU Yuanyuan, Associate Professor of the Department of Chemical and Biological Engineering and Associate Director of the Energy Institute at HKUST, found that the nanoscale groove traps at the perovskite grain’s triple junctions serve as geometric traps that capture cations and retard their interdiffusion towards homogenization. 

Researchers from China's Northwestern Polytechnical University, Chinese Academy of Sciences (CAS) and Henan University have addressed the stability challenge of flexible perovskite solar cells (FPSCs). Inspired by the exceptional wet adhesion of marine mussels via adhesive proteins (dopamine, DOPA), the scientists proposed a multidentate-cross-linking strategy, which combines multibranched structure and adequate dopamine anchor sites in three-dimensional hyperbranched polymer to directly chelate perovskite materials in multiple directions.

Schematics of key components for the underwater adhesion feature of marine mussels and HPDA adhesive in perovskite films and interfaces. Image from: Nature Communications

This constructs a vertical scaffold across the bulk of perovskite films from the bottom to the top interfaces, that intimately binds to the perovskite grains and substrates with a strong adhesion ability, and enhances mechanical durability under high humidity. 

Canon has developed a new high-performance material that addresses two issues of perovskite solar cells: photoelectric conversion efficiency and longevity. This new material can, according to Canon, do two things: prevent the halogen ion movement that causes the perovskite layer to deteriorate, and move the charge generated in the perovskite layer.

A real-world demonstration (through joint research with Toin University of Yokohama) has reportedly showed that when this newly developed material is applied between the perovskite and HTL layers to form a new layer, it can maintain a high rate of photo-electric conversion efficiency while increasing durability. The new layer covers the bumps in the perovskite layer, creating a smoother surface that enables the stable mass production of the perovskite solar cell. As it also improves durability, the burden of maintenance and repair is also reduced.

Forming a low-dimensional (LD) capping layer over the surface of three-dimensional (3D) perovskites is a known approach for stabilizing perovskite solar cells (PSCs). However, the performance of treated PSCs tends to be limited by inefficient charge transfer across the LD/3D interfaces.

Recently, researchers from China's Nanjing University of Aeronautics and Astronautics and University of Macau developed a 1D capping layer over the perovskite surface via post-treatment with a conjugated quinolinamine (QA) halide salt. In contrast to 2D perovskites, this unique configuration enables charge transfer between inorganic slabs and adjacent QA spacers in the capping layer, resulting in a reduced dielectric confinement effect and enhanced carrier mobility. 

An international research collaboration, led by Prof. Antonio Abate from Germany's Bielefeld University, has addressed the stability issue of perovskite solar cells by exploring the effects of multiple thermal cycles on microstructures and interactions between different layers of perovskite solar cells. They concluded that thermal stress is the decisive factor in the degradation of metal-halide perovskites. Based on this, they derived the most promising strategies to increase the long-term stability of perovskite solar cells.

In the experiment, perovskite solar cells were repeatedly cooled to minus 150 degrees Celsius and then heated to plus 150 degrees Celsius. The changes in the microstructure of the perovskite layer and the interactions with the neighboring layers were studied over the course of the cycles. © Li Guixiang

The international research collaboration has published the results of several years of work. Together with a team led by Prof. Meng Li, Henan University, China, and other partners in Italy, Spain, UK, Switzerland and Germany, they showed that thermal stress is the decisive factor in the degradation of metal-halide perovskites. "When used outdoors, solar modules are exposed to the weather and the seasons", says Abate. While encapsulation can effectively protect the cells from moisture and atmospheric oxygen, they are still exposed to quite large temperature variations day and night and throughout the year. Depending on the geographical conditions, temperatures inside the solar cells can range from minus 40 degrees Celsius to plus 100 degrees Celsius (in the desert, for example).

Researchers from Singapore's Nanyang Technological University and France's University of Lille (CNRS) have developed a biomass-derived furan-based conjugated polymer, PBDF-DFC, enabling a simplified direct precursor integration fabrication method for hybrid perovskite solar cells (HPSCs). 

Unlike traditional thiophene-based polymers, PBDF-DFC reportedly exhibits high solubility in perovskite precursor solvents, allowing direct incorporation into the precursor solution. This direct precursor integration approach could significantly streamline the fabrication process, reducing steps and potentially lowering production costs.