Mixed Dimensional 3D/1D Perovskites for Photovoltaic and Piezoresistive Optoelectronics

Vittorio Ferrara,^a Simone Virga,^a Giuseppe Arrabito,^a Michelangelo Scopelliti,^a Alessandro Longo,^b Francesco Giannici^a Bruno Pignataro^a

^a Department of Physics and Chemistry “Emilio Segrè”, Università degli Studi di Palermo, Viale delle Scienze, 90128 Palermo, Italy.

^b European Synchrotron Radiation Facility, 71, avenue des Martyrs, CS 40220, 38043 Grenoble Cedex 9, France and Consiglio Nazionale delle Ricerche, ISMN-CNR, I-90146 Palermo, Italy.

Mixed dimensional perovskite systems have attracted growing attention in the photovoltaic field, as they combine the complementary advantages of perovskites with different dimensionalities.^[1,2] 3D organic–inorganic hybrid perovskites are well known for their excellent photovoltaic performance, low-cost, and low-temperature solution processability, while lower dimensional (LD) perovskites, such as 2D or 1D structures, exhibit higher stability under environmental condition.^[3] Combining 3D and LD perovskites has proven to be an effective strategy for developing perovskite-based photoactive composites with high photovoltaic performance and enhanced durability, suitable for integration in innovative solar cells. In addition, LD perovskites can also offer the possibility of introducing additional functionalities.^[4] Recently, the newly synthesized series of 1D double perovskites of the type (TMSO)₃Sn₃ₓBi₂(1–ₓ)I₉, where TMSO stands for trimethylsulfoxonium and 0 ≤ x ≤ 1, has been reported to show interesting piezoresistive features.^[5] Here, the mix of methylammonium lead iodide chloride (MAPIC), a well-known high performance 3D perovskite, with the abovementioned 1D perovskite series has been investigated aiming to obtain durable high photoactive and piezorestitive thin films, for applications in solar cells. Firstly, the series of 1D perovskites deposited as thin film on flexible substrates were characterized by a multitechniques approach, based on UV-Vis absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM), then tested for their piezoresistive behavior by IV measurements at different bending angles. Then, such 1D perovskites were mixed and co-crystallized with MAPIC to obtain the mixed photoactive phases. Such mixes were characterized for their piezoresistivity, resulting in a stable electrical behavior upon bending, suggesting good properties for their use in flexible solar cells. The same 3D/1D mixed thin films were integrated in p-i-n perovskites solar cells successfully, showing a dependence of the power conversion efficiency (PCE) related to the amount of Sn²⁺ in the composite. In conclusion, the 3D/1D mixed perovskite systems will be further investigated and optimized to impart not only enhanced stability to the composite, but also additional functionalities for development of multifunctional thin films and advanced optoelectronic devices.