Suppressing Oxidation at Perovskite-NiOx Interface for Efficient and Stable Tin Perovskite Solar Cells

Cyano-Coordinated Tin Halide Perovskites for Wearable Health Monitoring and Weak Light Imaging

Low-toxicity tin halide perovskites with excellent optoelectronic properties are promising candidates for photodetection. However, tin halide perovskite photodetectors have suffered from high dark current owing to uncontrollable Sn2+ oxidation. Here, 2-cyanoethan-1-aminium iodide (CNI) is introduced in CH(NH2)2SnI3 (FASnI3) perovskite films to inhibit Sn2+ oxidation by the strong coordination interaction between the cyano group (C≡N) and Sn2+. Consequently, FASnI3-CNI films exhibit reduced nonradiative recombination and lower trap density. The self-powered photodetector based on FASnI3-CNI exhibits low dark current (1.04 × 10-9 A cm-2), high detectivity (2.2 × 1013 Jones at 785 nm), fast response speed (2.62 µs), and good stability. Mechanism studies show the increase in the activation energy required for thermal emission and generated carriers, leading to a lower dark current in the FASnI3-CNI photodetector. In addition, flexible photodetectors based on FASnI3-CNI, exhibiting high detectivity and fast response speed, are employed in wearable electronics to monitor the human heart rate under weak light and zero bias conditions. Finally, the FASnI3-CNI perovskite photodetectors are integrated with a 32 × 32 thin-film transistor backplane, capable of ultraweak light (170 nW cm-2) real-time imaging with high contrast, and zero power consumption, demonstrating the great potential for image sensor applications.

Colloidal Zeta Potential Modulation as a Handle to Control the Crystallization Kinetics of Tin Halide Perovskites for Photovoltaic Applications

Tin halide perovskites (THPs) have demonstrated exceptional potential for various applications owing to their low toxicity and excellent optoelectronic properties. However, the crystallization kinetics of THPs are less controllable than its lead counterpart because of the higher Lewis acidity of Sn2+, leading to THP films with poor morphology and rampant defects. Here, a colloidal zeta potential modulation approach is developed to improve the crystallization kinetics of THP films inspired by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. After adding 3-aminopyrrolidine dihydro iodate (APDI2) in the precursor solution to change the zeta potential of the pristine colloids, the total interaction potential energy between colloidal particles with APDI2 could be controllably reduced, resulting in a higher coagulation probability and a lower critical nuclei concentration. In situ laser light scattering measurements confirmed the increased nucleation rate of the THP colloids with APDI2. The resulting film with APDI2 shows a pinhole-free morphology with fewer defects, achieving an impressive efficiency of 15.13 %.

Electronically Manipulated Molecular Strategy Enabling Highly Efficient Tin Perovskite Photovoltaics

Buried interface modification can effectively improve the compatibility between interfaces. Given the distinct interface selections in perovskite solar cells (PSCs), the applicability of a singular modification material remains limited. Consequently, in response to this challenge, we devised a tailored molecular strategy based on the electronic effects of specific functional groups. Therefore, we prepared three distinct silane coupling agents, and due to the varying inductive effects of these functional groups, the electronic distribution and molecular dipole moments of the coupling agents are correspondingly altered. Among them, trimethoxy (3,3,3-trifluoropropyl)-silane (F3 -TMOS), which possesses electron-withdrawing groups, generates a molecular dipole moment directed toward the hole transport layer (HTL). This approach changes the work function of the HTL, optimizes the energy level alignment, reduces the open-circuit voltage loss, and facilitates carrier transport. Furthermore, through the buffering effect of the coupling agent, the interface strain and lattice distortion caused by annealing the perovskite are reduced, enhancing the stability of the tin-based perovskite. Encouragingly, tin PSCs treated with F3 -TMOS achieved a champion efficiency of 14.67 %. This strategy provides an expedient avenue for the design of buried interface modification materials, enabling precise molecular adjustments in accordance with distinct interfacial contexts to ameliorate mismatched energetics and enhance carrier dynamics.