Perovskite applications

Researchers at Chinese Academy of Sciences (CAS) have fabricated an intermediate recombination layer (IRL) featuring a heavily doped boron/phosphorus polysilicon tunneling junction, with tunnel oxide passivated contact (TOPCon) silicon cells serving as the bottom cell for perovskite/TOPCon tandem solar cells (TSCs). 

In perovskite/silicon TSCs, the IRL is an important structure electrically connecting the top-side perovskite and bottom-side silicon sub-cells, significantly influencing the overall device performance. The traditional IRL often uses ITO materials to ensure high transmittance and good electrical properties, which, however, usually leads to issues such as sputtering damage and low temperature process limitations.

The properties of 3D halide perovskites, such as mixed ionic–electronic conductivity and feasible ion migration, have enabled them to challenge traditional memristive materials. However, issues like poor moisture stability and difficulty in controlling ion transport due to their polycrystalline nature have hindered their use as a neuromorphic hardware. Recently, 2D halide perovskites have emerged as promising artificial synapses owing to their phase versatility, microstructural anisotropy in electrical and optoelectronic properties, and excellent moisture resistance. However, their asymmetrical and nonlinear conductance changes still limit the efficiency of training and accuracy of inference. 

Now, researchers from Seoul National University, Korea University, Sungkyunkwan University, Pohang University of Science and Technology and University of Southern California have achieved highly linear and symmetrical conductance changes in Dion–Jacobson 2D perovskites. 

Researchers from City University of Hong Kong, National Renewable Energy Laboratory (NREL) and Imperial College London have improved the long-term stability of perovskite solar cells with an atomic-layer deposition (ALD) method that replaces the fullerene electron transport layer with tin oxide. 

Professor Zhu Zonglong (left) and Dr Gao Danpeng of City University of Hong Kong hold their innovative solar cells. Image credit: Eurekalert

The team started by depositing the perovskite and the hole-transporter layer in a single step. Then, they used ALD to create an oxygen-deficient tin oxide layer to reduce the band offset to a thicker, overgrown layer of normal tin oxide. Solar cells had a power conversion efficiency of more than 25%, and they retained more than 95% of efficiency after 2000 hours of maximum power point operations at 65°C. 

Researchers from Thailand's Mahidol University, Rajamangala University of Technology Thanyaburi and Synchrotron Light Research Institute have presented two novel air-stable hole transporting materials (HTMs) based on a spiro[fluorene-9,9′-xanthene] (SFX) core functionalized with N-methylcarbazole (XC2-M) and N-hexylcarbazole (XC2-H) rings. 

These HTMs were synthesized via a straightforward, three-step process with good overall yields (∼40%) and low production costs. To further reduce device cost, carbon back electrodes were employed. The resulting PSCs, with a structure of FTO/SnO₂/Cs_0.05FA_0.73MA_0.22Pb(I_0.77Br_0.23)₃/HTM/C, achieved power conversion efficiencies (PCEs) of 13.5% (XC2-M) and 10.2% (XC2-H), comparable to the reference spiro-OMeTAD device (12.2%). 

Researchers at North Carolina State University and Brookhaven National Laboratory have reported a technique for engineering layered hybrid perovskites (LHPs) down to the atomic level, which enables precise control on how the materials convert electrical charge into light. 

Image credit: Matter

The technique opens the door to engineering materials tailored for use in next-generation printed LEDs, lasers and photovoltaic devices.

Slot-die coating (SDC) technology is a potential approach to mass produce large-area, high-performance perovskite solar cells (PSCs) at low cost. However, when the interface in contact with the perovskite ink has low wettability, the SDC cannot form a uniform pinhole-free perovskite film, which reduces the performance of the PSC.

Optimizing Slot-Die Coating for Commercial Solar Cell Production. Image credit: InfinityPV

Researchers from Korea's Jeonbuk National University have examined the correlation between interfacial roughness, wettability, and the overall efficiency of perovskite solar cells produced using slot-die-coating. This work offers a comprehensive understanding of how modifying the roughness of the hole transport layer (HTL) can improve the quality of perovskite films, enhance charge transport, and ultimately lead to high-efficiency perovskite solar cells with long-term stability.

Researchers from CHOSE (Centre for Hybrid and Organic Solar Energy) at Tor Vergata University of Rome, CNR-ISM and Saule Technologies have introduced an optimized blade coating process for the scalable fabrication of large-area (15 cm × 15 cm) perovskite solar modules with a nickel oxide hole transport layer, performed in ambient air and utilizing a non-toxic solvent system. 

The research group fabricated a 110 cm² perovskite solar module with an inverted configuration and a hole transport layer that uses nickel oxide instead of commonly utilized poly(triarylamine) (PTAA). The proposed architecture aims to achieve high efficiency that is competitive with PTAA-based panels while improving stability.

Soochow University researchers have proposed the in situ treatment of Cl-rich benzene phosphorus oxydichloride (BPOD)as a way to achieve high-quality pure-blue perovskites, by simultaneously enlarging the perovskite bandgap, passivating the halide vacancy defects, and immobilizing the halide ions through the hydrolysis products of chloride ions and phenylphosphonic acid. 

The background for this work is that despite the substantial progress in sky-blue (480−495 nm) perovskite light-emitting diodes (PeLEDs), pure-blue PeLEDs (<480 nm) merely show moderate performances. Bromide-chloride mixed perovskites may have potential to enable a straightforward and effective way to obtain pure-blue emission, but the tricky issue of halide migration in mixed halide perovskites makes it challenging to achieve efficient PeLEDs with stable electroluminescence (EL) spectra. 

Researchers from Duke University, University of Colorado - Boulder, Israel's Weizmann Institute of Science, Polish Academy of Sciences and University of Lille CNRS have examined the local structure of halide perovskites in their molten and glassy states, revealing the critical connection between these structures and the contrasting properties observed in their crystalline vs glassy states. 

The findings of this work enhance scientists' understanding of the diverse structural motifs in perovskites and how structural changes in perovskite glass impact their properties, paving the way for advancements in next-generation phase change materials and devices.

Researchers from China's Northwestern Polytechnical University, The Hong Kong University of Science and Technology, and Spain's Technical University of Madrid have developed a new lithium-free doping strategy to fabricate spiro-OMeTAD-based hole transport layers (HTLs) for applications in perovskite solar cell. A PV device built with a lithium salt-doped HTL achieved an efficiency of 25.45%.

Schematic illustration of a n-i-p PSC with spiro-OMeTAD HTLs doped by LiTFSI or Eu(TFSI)₂. Image from Nature Communications

The team's lithium-free doping strategy to fabricate a perovskite solar cell is based on a metal-free hole transport layer (HTL) made of spiro-OMeTAd that reportedly offers remarkable efficiency and stability levels. The research team explained that spiro-OMeTAD for perovskite cell applications is usually doped with a compound known as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) to enhance hole extraction and conductivity. This kind of doping, however, requires time-intensive air-oxidization for 24 hours, which reportedly represents an obstacle to the commercial production of perovskite PV devices.