A critical limitation of formamidinium lead iodide (FAPbI ₃ ) perovskite solar cells (PSCs) lies in the intrinsic instability of the ionic–covalent Pb–I octahedral lattice, relative to the unfavorable hexagonal δ-phase under operating conditions. We report an entropy-regulating molecular-lock strategy using 1-pyridin-3-ylmethyl-piperazine hydrochloride (3-PMPCl). Strong interactions between the perovskite lattice surface and 3-PMPCl modulate the rotational freedom of organic cations and suppress the detrimental entropy increase associated with [PbI ₆ ] ⁴⁻ octahedra disorder or expansion. This entropy-favored environment intrinsically increases the phase transition energy barrier. The uniform distribution and strong adsorption of 3-PMPCl stabilize the α-phase under elevated temperature and humidity conditions. We achieved a certified power conversion efficiency (PCE) of 27.6% in FAPbI ₃ -based PSCs. However, the operational stability of such champion devices remains below the state of the art. Adopting a stable bismuth electrode addresses this issue with a slight reduction in efficiency, yielding a device that retains 93.0% of its initial PCE (26.8%) after 1011 hours at 85°C under 1-sun illumination.

An all-solution two-step method for preparing wide-bandgap perovskites has the advantages of low cost, good repeatability and scalability. However, achieving high-quality wide-bandgap perovskite films via an all-solution two-step method remains challenging due to uneven distribution of halogens and incomplete reactions between organic salts and inorganic salts. Herein, we introduced tris(pentafluorophenyl)borane (BCF) into an inorganic layer resulting in boron–halide bonding, which stabilized uniform halide distribution and regulated the porous structure of the lead halide films, facilitating the diffusion of organic salts. Additionally, the fluorine substituents formed hydrogen bonds with organic cations, making BCF a bifunctional additive that delayed the reaction between the organic ammonium salt and the inorganic precursor, which was conducive to the growth of large-grained perovskite crystals. During the perovskite crystallization process, BCF molecules migrated to grain boundaries and the film surface, achieving a highly positive regulation influence on the nanoscale morphology and structure of the perovskite absorber films, thus leading to a pinhole-free, stress-free and less defect perovskite films. Ultimately, the approach enabled single-junction 1.68 eV wide-bandgap perovskite solar cells with a champion efficiency of 23.49% (certified 22.73%) and a V_OC of 1.291 V. Furthermore, the optimized perovskite films were pioneeringly and successfully integrated into monolithic perovskite/silicon tandem solar cells on textured silicon and achieved an efficiency of 31.12%, which is the highest value among tandem solar cells prepared by an all-solution two-step method, retaining >90% of initial performance after 500 hours of continuous operation.

Inverted perovskite solar cells with a p-i-n configuration have attracted considerable attention from the research community because of their simple design, insignificant hysteresis, improved operational stability, and low-temperature fabrication technology. However, this type of device is still lagging behind the classical n-i-p perovskite solar cells in terms of its power conversion efficiency. The performance of p-i-n perovskite solar cells can be increased using appropriate charge transport and buffer interlayers inserted between the main electron transport layer and top metal electrode. In this study, we addressed this challenge by designing a series of tin and germanium coordination complexes with redox-active ligands as promising interlayers for perovskite solar cells. The obtained compounds were characterized by X-ray single-crystal diffraction and/or NMR spectroscopy, and their optical and electrochemical properties were thoroughly studied. The efficiency of perovskite solar cells was improved from a reference value of 16.4% to 18.0–18.6%, using optimized interlayers of the tin complexes with salicylimine (1) or 2,3-dihydroxynaphthalene (2) ligands, and the germanium complex with the 2,3-dihydroxyphenazine ligand (4). The IR s-SNOM mapping revealed that the best-performing interlayers form uniform and pinhole-free coatings atop the PC₆₁BM electron-transport layer, which improves the charge extraction to the top metal electrode. The obtained results feature the potential of using tin and germanium complexes as prospective materials for improving the performance of perovskite solar cells.

Photo-switchable organic field-effect transistors (OFETs) represent an important platform for designing memory devices for a diverse array of products including security (brand-protection, copy-protection, keyless entry, etc.), credit cards, tickets, and multiple wearable organic electronics applications. Herein, we present a new concept by introducing self-assembled monolayers of donor–acceptor porphyrin–fullerene dyads as light-responsive triggers modulating the electrical characteristics of OFETs and thus pave the way to the development of advanced nonvolatile optical memory. The devices demonstrated wide memory windows, high programming speeds, and long retention times. Furthermore, we show a remarkable effect of the orientation of the fullerene–polymer dyads at the dielectric/semiconductor interface on the device behavior. In particular, the dyads anchored to the dielectric by the porphyrin part induced a reversible photoelectrical switching of OFETs, which is characteristic of flash memory elements. On the contrary, the devices utilizing the dyad anchored by the fullerene moiety demonstrated irreversible switching, thus operating as read-only memory (ROM). A mechanism explaining this behavior is proposed using theoretical DFT calculations. The results suggest the possibility of revisiting hundreds of known donor–acceptor dyads designed previously for artificial photosynthesis or other purposes as versatile optical triggers in advanced OFET-based multibit memory devices for emerging electronic applications.