Recently, Researcher Liu Xiaolong, a member of Professor Yang Zhimao's team at the Key Laboratory of Nonequilibrium Synthesis and Modulation of Condensed Matter, Ministry of Education, School of Physics, Xi'an Jiaotong University, has made significant phased advancements in collaboration with institutions such as Huaqiao University, Shandong University, the Institute of Chemistry, Chinese Academy of Sciences, and Qufu Normal University. Their work focuses on the preparation and photoelectric performance evaluation of pure-phase quasi-two-dimensional (Q-2D) and formamidinium-based three-dimensional (FA-3D) tin-based perovskite heterojunctions.

The research team devised a cooling growth method rooted in pre-synthesized polycrystalline materials, successfully fabricating MA-3D, FA-3D, and BEA-2D tin-based perovskite polycrystalline materials and bulk single crystals. Leveraging these, they formulated high-purity, high-stability precursor solutions. Through meticulous research into the composition, stability, and wettability variations among different precursor solutions, they discovered that the precursor solution derived from the BEAMA₃Sn₄I₁₃ crystal exhibited optimal stability.

Building upon this foundation, the team employed a residual heat-assisted spin-coating technique to fabricate pure-phase MA-Q-2D(n=4) tin-based perovskite films. These films boasted large grains, dense surfaces, uniform orientation, and high crystallinity. Notably, they retained their phase purity for at least one month within an argon glovebox. Among the various pure-phase MA-Q-2D(n=2, 3, 4)/FA-3D heterojunction films subsequently constructed, the MA-Q-2D(n=2)/FA-3D heterojunction stood out for its exceptional crystallinity. This structure effectively suppressed non-radiative recombination of carriers, showcasing superior carrier performance compared to both pure-phase FA-Q-2D(n=2)/FA-3D and FA-3D perovskites.

The pure-phase MA-Q-2D(n=2)/FA-3D tin-based perovskite solar cell, crafted based on this heterojunction, achieved a remarkable photoelectric conversion efficiency (PCE) of 14.33% and an open-circuit voltage of 0.80 V. These figures surpassed the 13.16% PCE and 0.74 V open-circuit voltage of the FA-Q-2D(n=2)/FA-3D device, with negligible hysteresis observed. Moreover, under ambient air conditions (with relative humidity below 30%), the encapsulated device demonstrated exceptional stability over a period exceeding 3000 hours. This achievement marks a significant milestone in the realm of MA-based tin-based perovskite photovoltaic devices.