Interfacial Defect Passivation and Stress Release via Multi-Active-Site Ligand Anchoring Enables Efficient and Stable Methylammonium-Free Perovskite Solar Cells
journal contributionposted on 2021-06-18, 15:05 authored by Baibai Liu, Huan Bi, Dongmei He, Le Bai, Wenqi Wang, Hongkuan Yuan, Qunliang Song, Pengyu Su, Zhigang Zang, Tingwei Zhou, Jiangzhao Chen
Interfacial trap-assisted non-radiative recombination and residual stress impede the further increase of power conversion efficiency (PCE) and stability of the methylammonium-free (MA-free) perovskite solar cells (PSCs). Here, we report an interfacial defect passivation and stress release strategy through employing the multi-active-site Lewis base ligand (i.e., (5-mercapto-1,3,4-thiadiazol-2-ylthio)acetic acid (MTDAA)) to modify the surface and grain boundaries (GBs) of MA-free perovskite films. Both experimental and theoretical results confirm strong chemical interactions between multiple active sites in the MTDAA molecule and undercoordinated Pb2+ at the surface or GBs of perovskite films. It is demonstrated theoretically that multi-active-site adsorption is more favorable thermodynamically as compared to single-active-site adsorption, regardless of PbI2 termination and formamidinium iodide (FAI) termination types. MTDAA modification results in much reduced defect density, increased carrier lifetime, and almost thoroughly released interfacial residual stress. Upon MTDAA passivation, the PCE is boosted from 20.26% to 21.92%. The unencapsulated device modified by MTDAA maintains 99% of its initial PCE after aging under the relative humidity range of 10–20% for 1776 h, and 91% after aging at 60 °C for 1032 h.
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Multi-Active-Site Ligand Anchoring ...GBPbI 2 terminationpower conversion efficiencyPCEdefect densitymulti-active-site Lewis base ligandperovskite filmsMTDAA passivation1032 hPSCMTDAA moleculeMA-free perovskite films1776 hgrain boundariesMTDAA modification resultsunencapsulated devicechemical interactionsdefect passivationsingle-active-site adsorptionInterfacial Defect Passivationsurfacecarrier lifetimetermination typesstress release strategyFAIStress Releaseformamidinium iodidehumidity rangemulti-active-site adsorptionStable Methylammonium-Free Perovski...