Rapid Crystallization for Efficient 2D Ruddlesden–Popper (2DRP) Perovskite Solar Cells

Abstract

Due to the additional introduction of bulky organic ammonium and the competition between bulky organic ammonium and methyl ammonium in 2D Ruddlesden-Popper (2DRP) perovskite, the crystallization process becomes complicated. Here, it is demonstrated that the rapid crystallization controlled by processing solvents plays an important role in achieving highquality 2DRP perovskite films. It is found that the processing solvents, e.g., dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), with a different polarity and boiling point, have almost no effect on crystal structure and phase distribution but have a remarkable effect on crystallization kinetics, crystal growth orientation, and crystallinity of 2DRP perovskite. Compared to polar aprotic solvent DMF and DMSO with a high boiling point, DMAC with low polarity and a suitable boiling point has a weak coordination to lead and ammonium salts and is easy to escape during solution processing, which is able to accelerate the crystallization rate of 2DRP perovskite. Benefitting from the rapid crystallization enabled high-quality 2DRP perovskite films, the best-performing device with improved stability and a power conversion efficiency of 12.15% is obtained using DMAC solvent. These findings may give guidance for solvent engineering for highly efficient 2DRP perovskite solar cells in the future.

Self‐Additive Low‐Dimensional Ruddlesden–Popper Perovskite by the Incorporation of Glycine Hydrochloride for High‐Performance and Stable Solar Cells

“…The slopes for BA ( n = 4) and Gly ( n = 4) perovskite devices are 1.68 and 1.42 kT / q , respectively ( k is Boltzmann's constant, T is temperature, and q is elementary charge), indicating that trap‐assisted recombination existed in the devices. [ 45–47 ] In comparison with that of BA ( n = 4) device, the slope of Gly ( n = 4) perovskite device is smaller and closer to 1 kT / q , which suggest lower trap‐assisted recombination. Therefore, low‐dimensional RP devices based on Gly ( n = 4) have higher V oc and thus higher PCE.…”

Oriented and Uniform Distribution of Dion–Jacobson Phase Perovskites Controlled by Quantum Well Barrier Thickness

“…The structure of the 2D layered perovskites is defined by the general formula A 2 A′ n − 1 M n X 3 n + 1 or AA′ n − 1 M n X 3 n + 1 , wherein the former, having monoammonium spacer cations, is named the Ruddlesden–Popper (RP) phase, and the latter, with diammonium spacer cations, is called the Dion–Jacobson (DJ) phase . At present, the research on RP phase perovskites is relatively mature, and various methods have been used to control crystal orientation and QW distribution, which are two critical factors influencing the performance. Hot casting was first reported to achieve vertical orientation, followed by the use of additives, shorter spacers, and the introduction of small amounts of FA + and Cs + .…”

Improving Charge Transport via Intermediate‐Controlled Crystal Growth in 2D Perovskite Solar Cells

“…Strategies to address this issue include controlling perovskite growth with more preferred vertical orientation or enhancing out‐of‐plane transport with new organic spacer design . For controlling perovskite growth with more preferred vertical orientation, researchers often use hot‐casting deposition method, incorporate additives to assist perovskite growth, or change the A‐sites to alter the crystal growth orientation . Although hot casting has led to high‐quality 2D perovskite films, it is difficult to have deterministic and precise control during fabrication.…”