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Optimization of the Ag/PCBM interface by Rhodamine interlayer to enhance efficiency and stability of perovskite solar cells


Effective control of the interface between the metal cathode and the electron transport layer (ETL) is critical for achieving high performance p-i-n planar heterojunction perovskite solar cells (PSCs). Several organic molecules have been explored as interlayers between the silver (Ag) electrode and the ETL for the improvement in the photovoltaic conversion efficiency (PCE) of p-i-n planar PSCs. However, the role of these organic molecules on the charge transfer at the metal/ETL interface and the chemical degradation processes of PSCs has not been yet fully understood. In this work, we systematically explore the effects of interfacial modification of the Ag/ETL interface on PSCs using Rhodamine 101 as a model molecule. Insertion of Rhodamine 101 as interlayer between Ag and fullerene derivatives (PC60BM and PC70BM) ETLs improve the PCE as well as the stability of p-i-n planar PSCs. Atomic force microscopy (AFM) characterization reveals that Rhodamine passivates the defects at the PCBM layer and reduces the band bending at the PCBM surface. In consequence, charge transfer from the PCBM towards the Ag electrode is enhanced leading to an increased fill factor (FF) resulting in a PCE up to 16.6%. Moreover, Rhodamine acts as a permeation barrier hindering the penetration of moisture towards the perovskite layer as well as preventing the chemical interaction of perovskite with the Ag electrode. Interestingly, the work function of the metal cathode remains more stable due to the Rhodamine incorporation. Consequently, a better alignment between the quasi-Fermi level of PCBM and the Ag work function is achieved minimizing the energy barrier for charge extraction. This work contributes to reveal the relevance of a proper interfacial engineering at the metal-cathode/organic-semiconductor interface.

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Publication details

The article was received on 08 Mar 2017, accepted on 01 Jun 2017 and first published on 05 Jun 2017

Article type: Paper
DOI: 10.1039/C7NR01678F
Citation: Nanoscale, 2017, Accepted Manuscript
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    Optimization of the Ag/PCBM interface by Rhodamine interlayer to enhance efficiency and stability of perovskite solar cells

    J. Ciro, S. Mesa, J. I. Uribe, M. A. Mejía Escobar, D. Ramirez, J. F. Montoya, R. Betancur, H. Yoo, N. Park and F. Jaramillo, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR01678F

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