Researchers from the Chinese Academy of Sciences (CAS), The Hong Kong University of Science and Technology and Harbin Engineering University have developed a crystal-solvate (CSV) pre-seeding strategy that significantly boosts both the efficiency and scalability of inverted perovskite solar cells (PSCs). The study demonstrates a new approach for regulating buried interfacial structures in solution-processed perovskite films - recognized as a major obstacle to stability and efficiency improvement.
Inverted PSCs, which reverse the conventional layer sequence by placing the hole-transport layer beneath the perovskite absorber, offer superior compatibility with scalable solution-processing methods. However, their performance has been limited by uncontrolled microstructure and electronic defects at the buried interface between the perovskite and the self-assembled monolayer (SAM). The new CSV pre-seeding method directly tackles this issue by introducing pre-deposited low-dimensional halide crystal-solvate (CSV) seeds - with the representative composition PDPbI₄·DMSO - onto SAM-modified substrates before perovskite deposition.
These anisotropic, rod-shaped CSV nanocrystals enhance the wettability of the otherwise hydrophobic SAM surface, enabling more uniform spreading of the perovskite precursor solution. During crystallization, the nanoseeds act as high-density heterogeneous nucleation centers, guiding the formation of perovskite grains from the bottom up. More intriguingly, solvent molecules (specifically DMSO) embedded within the CSV lattice are gradually released during thermal annealing, creating a lattice-confined solvent annealing environment. This localized in situ solvent microenvironment promotes grain reorganization and eliminates interfacial voids and nanogrooves.
The result is a compact, defect-suppressed perovskite bottom layer with electronically favorable band alignment for efficient hole extraction. Devices fabricated using this CSV pre-seeding method achieved a power conversion efficiency (PCE) of 26.13%, with a fill factor of 86.75%, alongside excellent light and thermal stability verified under ISOS-L-1 and ISOS-T-1 test protocols.
The technique shows strong scalability. When combined with a slot-die coating process, the team produced large-area perovskite mini-modules (49.91 cm² aperture area) that reached a record PCE of 23.15%, with only ~3% efficiency loss compared to small-area devices. This narrow gap represents a major advance in bridging laboratory results and industrial-scale photovoltaic manufacturing.
By precisely coupling induced crystallization with buried interface restoration, the CSV pre-seeding strategy sets a new benchmark for scalable, high-performance perovskite solar cells. The authors note that further tuning of organic cations and solvent components could expand the CSV material library, offering a flexible platform for next-generation interface engineering in perovskite photovoltaics and other soft-lattice optoelectronic systems.
