Technical / research

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. 

Researchers from Huaqiao University, Gold Stone (Fujian) Energy Company, Beijing Huairou Laboratory and Kunshan Shengcheng Photoelectric Technology have reported a four-terminal (4T) perovskite-silicon solar cell with a perovskite-based top cell, with an energy bandgap of 1.67 and lower surface defects. 

Structure of the 4T perovskite/silicon tandem solar cells. Image from Nature Communications

The team integrated a wide-bandgap perovskite solar cell with a hybrid back contact device in a four-terminal tandem cell that achieves high efficiency and stability. The group used a new surface passivation strategy that reportedly helped gain the cell's strong performance.

An international team of researchers from Bangladesh, USA and Saudi Arabia recently developed a structure that combines a double perovskite absorber layer (DPAL) of Ca₃NCl₃ and Ca₃SbI₃ with an electron transport layer (ETL) and hole transport layer (HTL) of CdS and CBTS via SCAPS-1D. 

The team's research demonstrated that the perovskite solar cell (PSC) with DPAL performs much better with the addition of HTL and is more efficient than single-layer PSCs. This work thoroughly examines the effect of thickness, doping levels, and defect densities of each layer on electrical parameters like VOC, JSC, FF, and PCE. 

Passivation of 3D perovskite light-harvesting layers with 2D perovskites is an effective strategy to boost the stability, PCEs and reliability of perovskite solar cells. These 2D layers can protect the light-harvesting layers, reducing their reactivity to environmental factors and thus preventing them from degrading quickly over time. 

Researchers from China's Wuhan University of Technology, Xidian University, University of Electronic Science and Technology of China and Germany's Technical University of Munich recently reported a strategy to prompt the formation of homogenous 2D perovskite passivation layers in perovskite-based solar cells. Using their proposed method, they achieved good active-area efficiencies and stabilities in perovskite solar modules based on formamidinium and cesium.

Researchers from South China University of Technology, The Chinese University of Hong Kong, Chinese Academy of Sciences (CAS), National Center for Nanoscience and Technology, Friedrich-Alexander University Erlangen-Nürnberg and Linköping University set out to eliminate deep traps in inorganic narrow bandgap (NBG) perovskites, in order to enable the successful development of 2T inorganic perovskite tandem solar cells (IPTSCs).

The team explained that all-inorganic perovskites prepared by substituting the organic cations (e.g. methylammonium (MA⁺) and formamidinium (FA⁺)) with inorganic cations (e.g. Cs⁺) are effective concepts to enhance the long-term photo- and thermal-stability of perovskite solar cells (PSCs). Hence, inorganic perovskite tandem solar cells (IPTSCs) are promising candidates for breaking the efficiency bottleneck and addressing the stability issue as well. However, challenges in fabricating 2-terminal (2T) IPTSCs due to the inferior film formation and deep trap states induced by tin cations hinder that option. 

Researchers from Spain's UPV/EHU, ICIQ-BIST, CIDETEC and Mexico's Instituto Politécnico Nacional have explored the effect of chalcogen substitutions in fullerene derivatives to enhance efficiency and stability of perovskite solar cells.

The team examined the effects of chalcogen substitution in the chemical structure of phenyl-butyric acid methyl ester (PCBM) on the performance and stability of inverted perovskite solar cells (PSCs). PCBMs are the most widely used electron transport materials in inverted PSCs. However, these compounds can suffer from lack of stability under irradiation. In the race for optimizing the PCBM-like derivatives, the thiophene moiety has garnered significant attention for enhancing the performance and stability of PSCs. The novelty in this study relies on the tests done on the selenophene derivative. This compound was compared to thiophene and furan substituted derivatives, and to the reference PCBM without a chalcogenophene moiety, demonstrating a better surface passivation and reduced interfacial charge recombination.

Carbon-based all-inorganic perovskite solar cells (C-PSCs) are known for their inexpensive manufacturing process. However, their perovskite constituents are susceptible to the formation of numerous structural defects and halide vacancies, which can induce substantial energy level misalignments between the light-absorbing layer and the carbon electrode. This discrepancy hinders the extraction and transfer of holes, thereby adversely affecting the overall efficiency of the device. 

Image credit: Chemical Engineering Journal

Researchers from China's Huaqiao University have proposed an interfacial post-treatment strategy aimed at reinforcing perovskite layers through the application of Neostigmine bromide (NMB) as a modifier. The team employed NMB to treat the upper interface of the perovskite, addressing intrinsic phase segregation, passivating surface defects, and filling halogen vacancies, thereby enhancing the photoelectric performance and stability of the device.

Aiming to explore the potential of sulfur-based additives for increasing both device power conversion efficiency and moisture stability of perovskite solar cells, researchers from BCMaterials (Spain), Huazhong University of Science and Technology (China), Max Planck Institute for Polymer Research (Germany) and CNRS (France) have reported a mechanism for the local nanoscopic humidity ingression into a multifunctional additiviated formamidinium-loaded halide perovskites.

a) The molecular structure of additives used. Image from: Advanced Energy Materials

By tuning the iodide and bromide tails of the additives, the influence of sulfur heteroatom containing ammonium-amidinium salts on the photo-physical and device properties of a formamidinium-rich perovskite absorber was uncovered. 

Researchers from China's Jiangxi Normal University, Chinese Academy of Sciences (CAS) and City University of Hong Kong have developed a self-driven X-ray detection device using high resistivity zero-dimensional lead-free perovskite ferroelectric single-crystal (NMP)₃Sb₂Br₉. The device exhibits an excellent self-driven X-ray detection performance, with an ultra-low detection limit of 84.1 nGyair/s, approximately 60 times lower than that of commercial α-Se (5500 nGyair/s).

The self-driven detection mode without external bias has been proven to be an effective means of reducing the limit of detection (LoD) due to its low current noise characteristics. Additionally, the zero-dimensional distinctive isolated framework results in a high resistivity of 1.39 × 1011 W cm, which effectively reduces the current noise and suppresses ion migration. 

Researchers from the Chinese Academy of Sciences (CAS), ShanghaiTech University, Zhejiang Laboratory and Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering recently reported an efficient (>27% reported efficiency) perovskite solar cell that uses a back mirror based on silver to improve light harvesting. 

The ultrathin perovskite solar cell utilizes a Gires-Tournois resonator to improve light absorption - an optical standing-wave resonator designed for generating chromatic dispersion. Gires-Tournois resonators are usually based on a reflective metal mirror and are primarily used in chirping applications such as pulse compression. The structure of the resonator in this study had a simple optical structure, combined with a silver back mirror, to optimize light capture and utilization while improving light absorption capacity.