Non-fullerene acceptors based organic solar cells represent the frontier of the field, owing to both the materials and morphology manipulation innovations. Non-radiative recombination loss suppression and performance boosting are in the center of organic solar cell research. Here, we developed a non-monotonic intermediate state manipulation strategy for state-of-the-art organic solar cells by employing 1,3,5-trichlorobenzene as crystallization regulator, which optimizes the film crystallization process, regulates the self-organization of bulk-heterojunction in a non-monotonic manner, i.e., first enhancing and then relaxing the molecular aggregation. As a result, the excessive aggregation of non-fullerene acceptors is avoided and we have achieved efficient organic solar cells with reduced non-radiative recombination loss. In PM6:BTP-eC9 organic solar cell, our strategy successfully offers a record binary organic solar cell efficiency of 19.31% (18.93% certified) with very low non-radiative recombination loss of 0.190 eV. And lower non-radiative recombination loss of 0.168 eV is further achieved in PM1:BTP-eC9 organic solar cell (19.10% efficiency), giving great promise to future organic solar cell research.

We demonstrate a monolithic perovskite/CIGS tandem solar cell with a certified power conversion efficiency (PCE) of 24.2%. The tandem solar cell still exhibits photocurrent mismatch between the subcells; thus optical simulations are used to determine the optimal device stack. Results reveal a high optical potential with the optimized device reaching a short-circuit current density of 19.9 mA cm^–2 and 32% PCE based on semiempirical material properties. To evaluate its energy yield, we first determine the CIGS temperature coefficient, which is at −0.38% K^–1 notably higher than the one from the perovskite subcell (−0.22% K^–1), favoring perovskite in the field operation at elevated cell temperatures. Both single-junction cells, however, are significantly outperformed by the combined tandem device. The enhancement in energy output is more than 50% in the case of CIGS single-junction device. The results demonstrate the high potential of perovskite/CIGS tandem solar cells, for which we describe optical guidelines toward 30% PCE.

We present a design strategy for fabricating ultrastable phase-pure films of formamidinium lead iodide (FAPbI ₃ ) by lattice templating using specific two-dimensional (2D) perovskites with FA as the cage cation. When a pure FAPbI ₃ precursor solution is brought in contact with the 2D perovskite, the black phase forms preferentially at 100°C, much lower than the standard FAPbI ₃ annealing temperature of 150°C. X-ray diffraction and optical spectroscopy suggest that the resulting FAPbI ₃ film compresses slightly to acquire the (011) interplanar distances of the 2D perovskite seed. The 2D-templated bulk FAPbI ₃ films exhibited an efficiency of 24.1% in a p-i-n architecture with 0.5–square centimeter active area and an exceptional durability, retaining 97% of their initial efficiency after 1000 hours under 85°C and maximum power point tracking.

Formamidinium lead triiodide (FAPbI ₃ ) is considered the most promising composition for high-performing single-junction solar cells. However, nonalloyed α-FAPbI ₃ is metastable with respect to the photoinactive δ-phase. We have developed a kinetic modulation strategy to fabricate high-quality and stable nonalloyed α-FAPbI ₃ films, assisted by cogenetic volatile iodine intercalation and decalation. The intercalation of iodine facilitated the formation of corner-sharing Pb-I framework building blocks and reduced the kinetic barrier for α-FAPbI ₃ formation, whereas the iodine decalation improved the final perovskite film quality in terms of composition purity and overall homogeneity. Solar cells based on this nonalloyed α-FAPbI ₃ (free of other extrinsic composition ions) achieved a power conversion efficiency of >24%. The devices also exhibited excellent durability, retaining 99% of their original power conversion efficiency after operating for more than 1100 hours at 85° ± 5°C under illumination.

The two-dimensional on three-dimensional (2D/3D) perovskite bilayer heterostructure can improve the stability and performance of perovskite solar cells. We show that the 2D/3D perovskite stack in a device evolves dynamically during its end-of-life decomposition. Initially phase-pure 2D interlayers can evolve differently, resulting in different device stabilities. We show that a robust 2D interlayer can be formed using mixed solvents to regulate its crystallinity and phase purity. The resulting 2D/3D devices achieved 25.9% efficiency and had good durability, retaining 91% of their initial performance after 1074 hours at 85°C using maximum power point tracking.