In the journey to obtain well-crystallized mixed tin (Sn) -lead (Pb) iodide perovskite films for solar cell application, great difficulties have been presented due to very different crystallization rates between...

Two-dimensional (2D) Ruddlesden−Popper perovskites films fabricated by solution process are composed of multiple 2D perovskite phases, and carrier transportation is limited by the low-n-value 2D perovskite phases (n=1 and n=2)....

Inverted‐structure perovskite solar cells (PSCs) are known for their superior device stability. However, based on nickel‐oxide (NiOx) substrate, disordered crystallization and bottom interface instability of perovskite film are still the main factors that compromise the power conversion efficiency (PCE) of PSCs. Here, 2D perovskite of thiomorpholine 1,1‐dioxide lead iodide (Td2PbI4) is introduced as a template to prepare 3D perovskite thin film with high crystal orientation and large grain size via a bottom‐up growth method. By adding TdCl to the precursor solution, pre‐crystallized 2D Td2PbI4 seeds can accumulate at the bottom interface, lowering the barrier of nucleation, and templating the growth of 3D perovskite films with improved (100) orientation and reduced defects during crystallization. In addition, 2D Td2PbI4 at the bottom interface also hinders the interfacial redox reaction and reduces the hole extraction barrier on the buried interface. Based on this, the Td‐0.5 PSC achieves a PCE of 22.09% and an open‐circuit voltage of 1.16 V. Moreover, Td‐0.5 PSCs show extremely high stability, which retains 84% of its initial PCE after 500 h of continuous illumination under maximum power point operating conditions in N2 atmosphere. This work paves the way for performance improvement of inverted PSCs on NiOx substrate.

Harmful Sn(IV) vacancies and uncontrolled fast crystallization commonly occur in tin–lead alloyed perovskite films. The typical dimethyl sulfoxide (DMSO) processing solvent is suggested to be the primary source of problems. Here, a DMSO‐free solvent strategy is demonstrated to obtain high‐performance Cs0.25FA0.75Pb0.5Sn0.5I3 solar cells. A rational solvent selection process via Hansen solubility parameters and Gutmann's donor number shows that N,N′‐dimethylpropyleneurea (DMPU) has a strong coordinate ability to form complete complexation with organic (formamidinium iodide) and inorganic (CsI, PbI2, and SnI2) components. This treatment suppresses the iodoplumbate (PbIn2‐n) or iodostannate (SnIn2‐n) preformed in precursor solution, thereby promoting pure intermediate complexes and retarding crystallization, realizing enlarged grain size, and improved film crystallinity. Additionally, it is demonstrated that DMPU‐based solvent system can further inhibit the oxidation of Sn(II) and reduced Sn(IV) content by nearly 75% due to its superior thermal and chemical stability. This DMSO‐free strategy generates a record efficiency of 22.41%, with a Voc of 0.88 V and a FF of 82.72% for the MA‐free Sn–Pb alloyed device. The unencapsulated devices display much‐improved humidity stability at 30 ± 5% relative humidity in air for 240 h, impressive thermal stability at 85 °C for 500 h, and promote continuous operation stability at maximum power point for 150 h.

The two-step crystallization method for perovskite film fabrication has been recognized as an efficient process to obtain high-performance perovskite solar cells (PSCs). However, many issues related to the as-prepared lead...