Ligand‐Anchoring‐Induced Oriented Crystal Growth for High‐Efficiency Lead‐Tin Perovskite Solar Cells

Abstract

The narrow bandgap (≈1.2 eV) Pb-Sn alloyed perovskite solar cell is a promising bottom component cell for all-perovskite tandem devices that are expected to offer higher efficiency than the theoretical Shockley-Queisser limit of the single-junction solar cells. The density functional theory (DFT) study reveals that the Pb-Sn perovskite film with the (100) orientation would render significantly reduced trap density, which is a critical figure-of-merit for perovskite device performance. Alkyl diamine is therefore designed to first anchor onto the surface as a nucleation agent to modulate the Pb-Sn perovskite growth to proceed preferentially along with the (100) orientation. It is observed that the diamine cations not only effectively induced the crystal growth at the nucleation stage, but also remained on the crystal surface to eventually passivate the resultant perovskite film. As a result, the diamine-based films show (100) preferred orientation with superior optoelectronic properties, as predicted by the DFT investigation. Consequently, the champion power conversion efficiency of 20.03% is achieved, one of the highest for this type of device. These findings provide a practicable strategy to theoretically design surface nucleation to induce preferential growth of perovskite material for better optoelectronic performance.

Modulating preferred crystal orientation for efficient and stable perovskite solar cells—From progress to perspectives

“…These ligands-anchored nuclei can serve as a surface template to successfully induce (100)-oriented crystal growth of Pb-Sn mixed perovskite (Figure 13D), resulting in a dramatically enhanced PCE of 20.03% from 16.23% for the control device. 114 Similarly, BA + and EA + cations have also been employed to achieve oriented growth of Sn and Pb-Sn perovskite films. 118,119 In addition, Liu et al 115 reported a soft template-controlled growth (STCG) method via introducing (adamantan-1-yl)methanammonium (ADMA) to modulate the nucleation and growth of all-inorganic CsPbI 3 perovskite.…”

“…Furthermore, a commonly overlooked but important point is that different crystal facets might possess various intrinsic trap states because the chemical structure of different crystal facets changes with crystal orientation. 111,114,117 Exploring the relationship between crystal orientation and trap states would strengthen knowledge of the correlation between crystallization kinetics and carrier dynamics, which is conducive to a more comprehensive understanding of the carrier transport behavior in PSCs. Furthermore, it is also of great significance to explore facet-dependent stability considering that different crystal facets could present various degrees of chemical stability.…”

“…In our previous work, we introduced diamine cations (EDA, PDA, and BDA) as surface anchoring ligands to connect adjacent nuclei to form a more stable microstructure than with monoamine cations. These ligands‐anchored nuclei can serve as a surface template to successfully induce (100)‐oriented crystal growth of Pb‐Sn mixed perovskite (Figure 13D), resulting in a dramatically enhanced PCE of 20.03% from 16.23% for the control device 114 . Similarly, BA + and EA + cations have also been employed to achieve oriented growth of Sn and Pb‐Sn perovskite films 118,119 .…”

“…(D) Schematic diagram of the PDA‐induced oriented growth of Pb‐Sn perovskite films. Reproduced with permission 114 . Copyright 2022, Wiley‐VCH.…”

Defect‐Dependent Crystal Plane Control on Inorganic CsPbBr3 Film by Selectively Anchoring (Pseudo‐) Halide Anions for 1.650 V Voltage Perovskite Solar Cells

“…This undoubtedly indicates that ionic liquids control the growth of CsPbBr 3 crystal along [h00] direction. [47] In addition, the orientation degree highly depends on the anion species by obeying an order of Cl − > BF 4 − > PF 6 − > NO 3…”