Presentation Details
| Mixed synergistic perovskite layer passivators for high-efficiency and stable solar cells Thierry Pauporté1, Zihao Li1, Cong Chen2. 1Chimie ParisTech, PSL University, Paris, France.2Hebei University of Technology, Tianjin, China |
Abstract
In recent years, solution-processed perovskite solar cells (PSCs) have developed rapidly due to their outstanding photovoltaic performance. The present record certified power conversion efficiency (PCE) has reached 27%. Particularly, p-i-n inverted PSCs have achieved remarkable advancements in operational stability and PCE. In PSCs, the mismatch between quasi-Fermi level splitting (QFLS) and open-circuit voltage (VOC) is highly detrimental to the performance of perovskite solar cells. Understanding and mitigating this loss pathway is therefore pivotal for achieving high power conversion efficiency. Herein, we propose a synergistic passivation strategy to suppress the QFLS–VOC mismatch that commonly arises in devices passivated with a non-conjugated single molecule, piperazine diiodide. While piperazine diiodide effectively suppresses interfacial recombination, the resulting passivated films suffer from a heterogeneous surface photo-potential distribution. We demonstrate that the incorporation of conjugated molecules markedly homogenizes and enhances the surface photovoltage across the entire film and induces the formation of a robust cationic-type (–NH3+) passivation layer. This dual molecule passivation simultaneously passivates recombination defects and improves charge separation efficiency. By implementing bimolecular passivation approach through the combined use of piperazine- and a thiophene-derived iodide in p-i-n devices, we achieved a champion PCE of 27.18% (certified steady-state PCE of 26.47%), together with outstanding operational stability. Notably, encapsulated devices, optimized for stability, retained over 98.6% of their initial efficiency after 2400 h of continuous illumination. The approach can be generalized to other non-conjugated molecules for the treatment of the perovskite layer. It affords a novel perspective of optimizing surface passivation of perovskite surface and is an effective approach to enhance efficiency and stability of perovskite related devices.
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