Controlled Crystallization of CsRb‐Based Multi‐Cation Perovskite Using a Blended Sequential Process for High‐Performance Solar Cells

Abstract

High‐quality perovskite films with low defect densities and high carrier‐diffusion lengths are essential for high‐performance perovskite devices. Herein, a modified two‐step sequential method is proposed, in which equal amounts of Cs+ and Rb+ ions (Cs+Rb+) are added to a PbI2 solution in the first step of perovskite deposition. The incorporation of Cs+Rb+ results in trace amounts of δ‐CsPbI3, leading to a reduction in the grain size in the PbI2 layer that facilitates better penetration of the organic salts in the second step of the precursor deposition. Meanwhile, the low density of the δ‐CsPbI3 crystals act as seeds to regulate the nucleation and growth of the perovskite crystals. A single‐layered columnar large‐grain perovskite film is obtained. The addition of Cs+Rb+ promotes crystal growth along the (100) orientation, which is beneficial for the reduction of surface defects. The incorporated Rb+ ions can regulate the remaining PbI2 in the perovskite. The improved quality of the perovskite film results in a significantly prolonged carrier lifetime of ≈7.01 μs and an enhanced electron diffusion length of ≈2.84 μm. As a result, the photovoltaic parameters are all improved in the established devices and a power conversion efficiency of 21.49% is reached.

Optimization of a SnO2-Based Electron Transport Layer Using Zirconium Acetylacetonate for Efficient and Stable Perovskite Solar Cells

“…In this work, the mixed cation perovskite Cs 0.035 Rb 0.035 FA 0.66 MA 0.27 PbI 2.73 Br 0.1 Cl 0.17 was deposited via a blended sequential deposition procedure previously reported. 43 We used double-layered electrontransport materials in the PSCs, as shown in Figure 1a. In the first step, solutions of different concentrations (0.2, 0.3, 0.5, 0.8, 1.0, and 1.5 mg/mL) of the ZrAcac precursor were deposited onto the processed, clean ITO substrate via spincoating at a speed of 5000 rpm/s for 30 s. Then, the ZrAcac layer was obtained by annealing at 100 °C for 10 min on a hot plate.…”

“…In this work, the mixed cation perovskite Cs 0.035 Rb 0.035 FA 0.66 MA 0.27 PbI 2.73 Br 0.1 Cl 0.17 was deposited via a blended sequential deposition procedure previously reported . We used double-layered electron-transport materials in the PSCs, as shown in Figure a.…”

“…The preparation methods of the SnO 2 , perovskite, and PTAA precursor solutions refer to our previous work. 43 Solar Cell Fabrication. ITO glass substrates were cleaned with detergent for 2 h and then washed with deionized (DI) water to remove the detergent.…”

“…The preparation methods of the SnO 2 , perovskite, and PTAA layers refer to our previous work. 43 Finally, an Au film (ca. 100 nm) was prepared by thermal evaporation.…”

“…The ZrAcac precursor solution was prepared by dissolving a series of concentrations of ZrAcac in ethanol. The preparation methods of the SnO 2 , perovskite, and PTAA precursor solutions refer to our previous work …”