Inverted perovskite solar cells reverse the positions of the electron and hole transport layers, offering strong power conversion potential and good compatibility with scalable solution processing techniques, but their performance and long term stability have been constrained by poorly controlled microscopic structures and electronic defects at the buried bottom interface where the perovskite contacts the hole transport layer.
A team at the Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT) of the Chinese Academy of Sciences has now developed a crystal solvate (CSV) pre seeding method that enables precise regulation of this critical bottom interface, opening a path toward high efficiency, large area perovskite photovoltaic modules.
The work, reported in the journal Nature Synthesis on February 27, introduces a strategy in which custom designed low dimensional halide crystal solvate seeds with the formula PDPbI4-DMSO are pre deposited on self assembled monolayer (SAM) modified substrates before the perovskite layer is formed.
These CSV nanocrystals, which have an anisotropic rod like shape, act as a structural template for subsequent perovskite crystal growth and significantly enhance the wettability of the otherwise hydrophobic SAM surface, allowing the perovskite precursor solution to spread uniformly across the substrate.
During crystallization, the pre seeded nanocrystals provide abundant heterogeneous nucleation sites that accelerate perovskite formation and promote more controlled crystal growth throughout the film.
A key innovation in the approach is the role of dimethyl sulfoxide (DMSO) solvent molecules locked within the CSV crystal structure, which are released in a controlled manner during thermal annealing.
As the DMSO leaves the lattice, it generates a localized "lattice confined solvent annealing" microenvironment at the buried interface that gently reorganizes and grows the perovskite grains, working together with the seed induced crystallization process.
According to co first author Dr Sun Xiuhong, this integrated method tackles both crystallization regulation and interface stabilization in a single scheme and delivers strong performance even at buried interfaces that are typically very difficult to engineer with precision.
By eliminating interfacial voids and smoothing grain boundary grooves, the CSV pre seeding process produces a dense, highly oriented perovskite bottom layer with improved electronic properties and enhanced photothermal stability compared with films prepared without the treatment.
The researchers then combined the CSV pre seeding concept with a slot die coating process and fabricated a perovskite solar mini module with an aperture area of 49.91 square centimeters, achieving a power conversion efficiency of 23.15 percent.
The efficiency loss between small area cells and this larger mini module was kept below 3 percent, a result that compares favorably with many previously reported perovskite module demonstrations and addresses a long standing scaling bottleneck linked to size effects.
"This technology overcomes the longstanding scaling bottleneck caused by size effects through the combination of induced crystallization and buried interface restoration," said Prof Pang Shuping, noting that the method offers benefits not only for efficiency but also for large area device uniformity.
Beyond its direct application in perovskite photovoltaics, the team views the crystal solvate pre seeding concept as a versatile materials platform in which organic cations and solvent molecules can be tuned to design a broad library of CSV materials tailored for different interfaces.
The researchers suggest that this paradigm for buried interface engineering could extend to other soft lattice semiconductor optoelectronic devices where precise control of interfacial microstructure, defect density and stability is crucial for long term performance.
Research Report:Crystal-solvate pre-seeding strategy for buried interface regulation in inverted perovskite solar cells
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Qingdao Institute of Bioenergy and Bioprocess Technology
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