Perovskite Surface Passivation Using Thiophene-Based Small Molecules for Efficient and Stable Solar Cells

Abstract

The suppression of perovskite surface defect recombination is very critical in obtaining high-efficiency perovskite solar cells (PSCs). Ammonium salts with long carbon chains or forming two-dimensional (2D) perovskites are usually used to passivate defects. However, they might limit carrier extraction or transport due to the electrical insulation of long-chain organic ligands. Herein, we propose a small molecule of thiophene-2-acetamide (TAA) to passivate surface defects of a methylammonium lead iodide (MAPbI 3 , where MA is methylammonium) perovskite film. The results suggest that the S atom of thiophene suppresses Pb 0 defects and the −C�O group passivates the uncoordinated Pb 2+ by forming chemical bonds with Pb 2+ . The −NH 2 group further enhances the interaction between TAA and perovskite surface defects by forming hydrogen bonds with I − . Moreover, carrier extraction is promoted significantly from the perovskite film to the hole-transport layer. The incorporation of the TAA additive is found to enhance the crystallization of films via a strong interaction between the −C�O group and Pb 2+ of the perovskite precursors. The synergistic effect of surface passivation and enhanced crystallization has been successfully demonstrated in the champion MAPbI 3 PSCs, resulting in a significantly enhanced conversion efficiency from 18.35% to 20.62%. Notably, the device stability under 1-sun illumination and high humidity (∼85%) in air has significantly been improved.

Healing the Buried Interface by a Plant-Derived Green Passivator for Carbon-Based CsPbIBr2 Perovskite Solar Cells

“…Therefore, we first calculated the electrostatic potential distribution of the ET molecule, which theoretically reflects the in-service groups to interact with undercoordinated Pb 2+ in the perovskite lattice. As presented in Figure a,b, there is an electron affinity difference for various atoms, therefore, parts of electrons in the conjugated carbon skeleton could transfer to S and O atoms, forming negative electrostatic centers with higher electron density, which donate long-pair electrons to undercoordinated Pb 2+ through a typical Lewis base–acid reaction. − To further clarify the interaction, we then constructed the V I defect-dominated structure models without and with ET molecules and calculated the charge distribution. As shown in Figure c,d, it is obvious that the localized charge traps caused by undercoordinated Pb 2+ are effectively delocalized over the whole lattice based on the 3D charge density redistribution profiles (yellow and cyan clouds mean electron accumulation and depletion, respectively) and electron localized function (ELF) patterns, demonstrating the formation of coordination bonds with Pb 2+ .…”

Mn-Doped CsPbCl3 Perovskite Nanocrystal via Surface Engineering with Thiophene-2-Carboxylic Acid: Implications for Photoresponse Study

“…In recent years, thiophene-based molecules have attracted considerable attention for their unique electronic properties, excellent charge transport abilities, and chemical stability. Thiophene 2-carboxylic acid (C 5 H 4 O 2 S) (TCA) has shown promise as an effective surface engineering agent for various perovskite systems. , TCA contains a carboxylic acid group that can readily bind to the perovskite surface, forming a passivating layer that mitigates surface defects and suppresses nonradiative recombination. − …”