Stability

Researchers from China's Wuhan University and Hubei University have examined the long-term stability problem of tin-lead perovskites under irradiation, counterintuitively discovering an irreversible phase reconstruction process. 

The evolution from tin-lead perovskites to a reconstruction of lead perovskites under light. Image from: Nature Communications

Tin-lead perovskite materials show promise for all-perovskite tandem solar cells, offering an optimal bandgap that significantly boosts power conversion efficiency. However, light-induced degradation, particularly in ambient air, remains a major obstacle to their long-term stability. Unlike single-metal perovskite materials, tin-lead perovskite degrades through distinct mechanisms, making it crucial to understand how it deteriorates under light and air exposure.

Researchers from China's Xi’an Jiaotong University, Huazhong University of Science and Technology, Fudan University, ULVAC-PHI Instruments, National University of Singapore (NUS), Sweden's Uppsala University and EPFL have developed a self-assembled bilayer (SAB) that can be used as a hole contact material that grants improved adhesive contact with the perovskite film. 

A schematic illustration of the inverted PSCs. Image from: Nature Energy

The team went on to fabricate an inverted perovskite solar cell that utilizes the self-assembled bilayer (SAB) as a hole-selective molecular contact. The cell was made with a substrate made of glass and transparent conductive oxides (TCOs), the proposed bilayer, the perovskite absorber, an ETL based on buckminsterfullerene (C60), a bathocuproine (BCP) buffer layer, and a silver (Ag) metal contact. 

When it comes to innovation in advanced materials, Solaveni GmbH stands out as a company with a bold mission. Founded in 2021 as a subsidiary of Saule Technologies, Solaveni was created with a vision to revolutionize the world of perovskite-based materials by focusing on sustainable chemistry and environmental responsibility. Today, the company is carving out a space in fields like printed electronics, energy harvesting, storage, and solid-state lighting, all while ensuring its processes remain green and future-ready.

At the heart of Solaveni’s journey is its CEO, Dr. Senol Öz, whose expertise and passion for perovskite technology have been key to the company’s progress. Senol’s career spans over a decade of research and hands-on experience in solution-processing and chemical engineering of perovskite solar cells. From his doctoral work in Germany, to his postdoctoral research in Japan, and eventually joining Saule Technologies, his path has been defined by a deep commitment to advancing perovskite materials.

We had the opportunity to sit down with Senol for an insightful Q&A, where he shared his thoughts on Solaveni’s vision, the challenges of perovskite technology, and the future of sustainable material production. Let’s dive into the conversation!

Solaveni was established in 2021 as a subsidiary of Saule Technologies, one of the pioneers in the perovskite solar industry. Why did Saule decide to establish a materials subsidiary?

Saule Technologies, a trailblazer in the perovskite solar industry, founded Solaveni in 2021 to address the burgeoning demand for high-quality, innovative materials critical to advancing solar technology. The establishment of Solaveni reflects Saule’s strategic vision to enhance and diversify its capabilities within the renewable energy sector. By creating a specialized subsidiary, Saule aims to streamline the development and production of materials relevant for the perovskite ecosystem, ensuring consistent quality and fostering innovation.

Imec, partner in EnergyVille, in collaboration with the University of Cyprus, has demonstrated long-term outdoor stability of perovskite solar modules. Mini-modules of 4 cm², developed at imec/EnergyVille, were comprehensively evaluated over two years in real-world conditions in Cyprus, with a remarkable power efficiency retention of 78% after one year, which current perovskite solar modules only retain for weeks. These promising findings are among the first real-world results to address the stability issues that currently hinder perovskite solar cells from commercialization.

Standard indoor testing in a controlled environment, which continuously mimics sun irradiation, only serves as a proxy for real-world performance. Environmental conditions, such as varying light, temperature and weather, impact cell performance. Despite this, only a handful of research groups have investigated outdoor performance of perovskite PV, focusing primarily on small cells rather than modules. Over the last two years, imec conducted a comprehensive study of the outdoor performance of their perovskite PV modules. 

The interfaces of each layer in perovskite solar cells (PSCs) have a significant impact on the charge transfer and recombination. Especially, the interface between perovskite and the hole transport layer (HTL) in p-i-n type PSCs significantly affects the contact characteristics between the HTL and perovskite, hindering further improvements in performance and stability. 

Researchers from South China University of Technology and Guangxi University have introduced a small molecule 9-Fluorenylmethoxycarbonyl chloride (9-YT) as a molecule bridge for p-i-n PSCs, which enhances the interaction between self-assembly molecules (SAMs) and perovskite. 

Researchers from The Hong Kong Polytechnic University, Beijing Institute of Technology and University of California Los Angeles have addressed the fragile and moisture-sensitive nature of halide perovskite materials by using an asynchronous cross-linking strategy. 

Schematic illustration of intermediate-dominated perovskite crystallization by pre-embedded DVS and all-around co-polymerization protection through the post-treatment of gly. Image credit: Nature Communications

A multifunctional cross-linking initiator, divinyl sulfone (DVS), is firstly pre-embedded into perovskite precursor solutions. DVS facilitates intermediate-dominated perovskite crystallization manipulation, favoring formamidine-DVS based solvate transition. Subsequently, DVS-embedded perovskite as-cast films are post-treated with a nucleophilic reagent, glycerinum, to trigger controllably three-dimensional co-polymerization. The resulting cross-linking scaffold provides enhanced water-resistance, releases residual tensile strain, and suppresses deep-level defects. 

Researchers from Wake Forest University, SUNY University at Buffalo and Technical University of Dresden have addressed the issue of perovskites' susceptibility to environmental degradation and reliance on toxic solvents in traditional processing methods, by introducing methylammonium lead iodide (MAPbI₃) perovskite films that are processed via a solvent-free laser printing technique. The films produced using this method reportedly exhibit exceptional stability and can withstand extreme conditions.

Instead of using solvents, the team created a dry powder by combining methylammonium lead iodide (the perovskite semiconductor) with carnauba wax and microscopic silica particles. Using a modified laser printer, they deposit this powder in precise patterns. The laser's heat briefly melts the mixture, allowing it to reform into a layered structure.

Researchers from City University of Hong Kong have introduced a novel and durable 2D thermochromic perovskite, Tha₂MAPbI₄ (TMPI, Tha = thiourea, MA = methylamine), wherein Tha acts as a Lewis acid-base adduct. TMPI demonstrates a reversible transition, achieving 83.7% luminous transmittance in the cold state and 35.2% in the hot state, thereby showcasing a substantial solar modulation ability of 24.7%. 

The background for this development is that despite growing interest in thermochromic metal halide perovskite (MHPs) for smart window applications, existing MHP smart windows predominantly feature 3D perovskite, which exhibits a deficiency in environmental stability, presenting persistent challenges for practical applications. 

In November 29, Hangzhou Xianna Optoelectronic Technology Co., Ltd. delivered its perovskite α-tandem modules for the China Three Gorges New Energy 50 MW PV demonstration project, in what is said to mark the first commercial application of four-terminal perovskite-silicon tandem modules in China. 

Once the PV power plant utilizing these tandem modules is completed and connected to the local grid, it will significantly alleviate the local grid's supply-demand imbalance, reduce environmental pollution, and improve air quality. The design work for a 500 kW demonstration plant has already been completed, with plans to collaborate with engineering institutes for on-site module layout design. The demonstration plant is expected to be connected to the grid and operational by the end of 2024.

Researchers from China's Tianjin University of Technology, Zhejiang Sci-Tech University, University of Electronic Science and Technology of China, North China Electric Power University and South China University of Technology have shown that the introduction of azetidinium iodide (AZI) into the precursor solution of a 1.77 eV bandgap FA_0.8Cs_0.2Pb(I_0.6Br_0.4)₃ perovskite significantly improves the efficiency and stability of the perovskite cells. 

Devices fabricated with 2 mol% AZI (relative to FAI, noted as AZ2) in perovskite layer exhibited a high PCE of 19.16 % and a high open-circuit voltage of 1.31 V. When stored under nitrogen atmosphere and illuminated under 1 sun conditions for 300 h, AZ2 device retained 80 % of the initial values.