Chlorine Bulk and Surface Passivation Strategy to Boost FAPbI3 Solar Cell Efficiency

Valentina Larini^a, Matteo Degani^a, Zahra Andaji-Garmaroudi^b, Giovanni Pica^a, Changzeng Ding^c, Fabiola Faini^a, Samuel D. Stranks^b, Chang-Qi Ma^c, Giulia Grancini^a

^aDepartment of Chemistry, University of Pavia, Italy

^bCavendish Laboratory University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK

^cInnovation Laboratory & Printable Electronics Research Center, Suzhou Institute of Nano- Tech and Nano-Bionics (SINANO)

NIPHO
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO22)

Online, Spain, 2022 February 14th - 15th

Organizers: Giulia Grancini, Mónica Lira-Cantú and Silvia Colella

Poster, Valentina Larini, 027
Publication date: 11th November 2021

ePoster:

Perovskite solar cells (PSCs) have witnessed a rapid advance in the last years, reaching at present a certified maximum photovoltaic conversion efficiency (PCE) of 25.5%.^[1] Despite the massive progresses attained by the scientific community, defect-mediated recombination losses still limit the open-circuit voltage (V_OC) of the devices, hence affecting their PCE.^[2] Bulk and dimensional engineering, which consists in the generation of a low-dimensional perovskite (LPD) at the perovskite/charge transporting layer interface, have been employed to reduce defects and improve the device performance.^[3-7]

In our work, we combined both strategies to boost the efficiency of formamidinium lead iodide (FAPbI₃)-PSCs, introducing methylammonium chloride (MACl) in the bulk (at 20% concentration with respect to FAPbI₃) and synthesizing a LDP at the perovskite/spiro-OMeTAD interface, depositing a solution of 4-methylphenethylammonium chloride (MePEACl) in isopropyl alcohol onto the surface of FAPbI₃, fabricated with 1% of lead iodide excess. Cells produced with non-treated FAPbI₃ were adopted as reference devices and the sole bulk treatment was compared to the double bulk and surface passivation.

Structural and morphological investigations show that MACl promotes the preferential growth of the black, cubic α-FAPbI₃ over the yellow, unwanted δ-phase and favors the growth of bigger grains.

The formation of a LDP phase over the bulk treated-FAPbI₃ is demonstrated by a peak at 2θ=5.0° in the X-ray diffraction pattern of the perovskite film and by the presence of minor photoluminescence (PL) peaks at 512 nm and 567 nm in the FAPbI₃ (MACl) + MePEACl PL spectrum, which we correlate to distinct low-dimensional phases.

Electroluminescence spectra and PL maps, acquired at the maximum PL peak emission wavelength, show a progressive enhancement in the EL and PL signal intensity upon MACl addition and after the combined MACl and MePEACl treatment.

Statistical analyses of the photovoltaic parameters displayed by PSCs fabricated with bare-FAPbI₃, bulk treated-FAPbI₃ and bulk and surface engineered-FAPbI₃ reveal a boost in the V_OC, short-circuit current density (J_SC) and fill factor (FF) values, in accordance with the improved morphological, structural and optical properties of the active layer.

In conclusion, employing two chlorine-based compounds, we demonstrated that the combination of bulk and surface passivation strategies successfully enhances the efficiency of FAPbI₃-PSCs, leading to a champion 21.4% PCE.

References:

[1] Zuo, C.; Bolink, H. J.; Han, H.; Huang, J.; Cahen, D.; Ding, L. Advances in Perovskite Solar Cells. Adv. Sci. 2016, 3, 1500324

[2] Liang, L.; Luo, H.; Hu, J.; Li, H.; Gao, P. Efficient Perovskite Solar Cells by Reducing Interface-Mediated Recombination: a Bulky Amine Approach. Adv. Energy Mater. 2020, 10, 2000197

[3] Mahmud, M. A.; Pham, H. T.; Duong, T.; Yin, Y.; Peng, J.; Wu, Y.; Liang, W.; Li, L.; Kumar, A.; Shen, H.; Walter, D.; Nguyen, H. T.; Mozaffari, N.; Tabi, G. D.; Andersson, G.; Catchpole, K. R.; Weber, K. J.; White, T. P. Combined Bulk and Surface Passivation in Dimensionally Engineered 2D-3D Perovskite Films via Chlorine Diffusion. Adv. Funct. Mater. 2021, 31, 2104251

[4] Zhang, C.; Wu, S.; Tao, L.; Arumugam, G. M.; Liu, C.; Wang, Z.; Zhu, S.; Yang, Y.; Lin, J.; Liu, X.; Schropp, R. E. I.; Mai, Y. Fabrication Strategy for Efficient 2D/3D Perovskite Solar Cells Enabled by Diffusion Passivation and Strain Compensation. Adv. Energy Mater. 2020, 10, 2002004

[5] Sutanto, A. A.; Drigo, N.; Queloz, V. I. E.; Garcia-Benito,I.; Kirmani, A. R.; Richter, L. J.; Schouwink, P. A.; Cho,K. T.; Paek, S.; Nazeeruddin, M.K.; Grancini, G. J. Mater. Chem. A 2020, 8, 2343

[6] Ye, J.Y.; Tong, J.; Hu, J.; Xiao, C.; Lu, H.; Dunfield, S.P.; Kim, D.H.; Chen, X.; Larson, B.W.; Hao, J.; Wang, K.; Zhao, Q.; Chen, Z.; Hu, H.; You, W.; Berry, J.J.; Zhang, F.; Zhu, K. Enhancing Charge Transport of 2D Perovskite Passivation Agent for Wide-Bandgap Perovskite Solar Cells Beyond 21%. Sol. RRL 2020, 4, 2000082

[7] Zhang, H.; Wang, S.; Hou, Y.; Zhang, F.; Hao, Y.; Song, J.; Qu, J. Comparison of surface-passivation ability of the BAI salt and its induced 2D perovskite for high-performance inverted perovskite solar cells. RSC Adv. 2021, 11, 23249

Acknowledgements:

The authors acknowledge the “HY-NANO” project that received funding from the European Research Council (ERC) Starting Grant 2018 under the European Union’s Horizon 2020 research and innovation program (Grant Agreement No. 802862) and the Fondazione Cariplo Economia Circolare 2021 Project “Green flexible hybrid perovskite solar module for the market: from smart lead manipulation to recycling” (FLHYPER, no 20201067) , funded under the “Circular Economy-2020” call and the Nano-X from Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (SINANO) for the technical support (Project No. A2107). The authors acknowledge the Royal Society and Tata Group (UF150033) and EPSRC (EP/R023980/1) for funding.

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