Evaluation of active layer thickness influence in long-term stability and degradation mechanisms in CsFAPbIBr perovskite solar cells
Mari Carmen López González a, Gonzalo del Pozo Melero a, Diego Martín Martín a, Laura Muñoz Díaz a, José Carlos Pérez Martínez a, Enrique Hernández Balaguera a, Belén Arredondo Conchillo a, Yulia Galagan b, Mehrdad Najafi c, Beatriz Romero Herrero a
a Universidad Rey Juan Carlos, Calle Tulipan s/n, Móstoles, Spain
b National Taiwan University, No.1, Sect 4, Roosevelt Rd, Taipei, Taiwan, Republic of China
c TNO Solliance
International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics (HOPV22)
València, Spain, 2022 May 19th - 25th
Organizers: Pablo Docampo, Eva Unger and Elizabeth Gibson
Poster, Mari Carmen López González, 205
Publication date: 20th April 2022

Over the last few decades, perovskite solar cells (PSCs) have been widely studied due to their excellent optoelectronic properties [1], reaching a certified power conversion efficiency (PCE) of 25.5% in 2021. Nevertheless, one of the main challenges for their commercialization is to solve their instability issues [2], mainly originated from the degradation of the perovskite active layer as well as the degradation of the interfaces and electrodes. A thorough understanding of the processes taking place in the device is key for the development of this technology. On the other hand, the active layer thickness is one of the most important parameters to optimize the device layer structure. Indeed, there is a trade-off between light absorption, which increases with perovskite thickness, and charge extraction, which can be limited in thicker active layers, due to inefficient carrier transport or reduced charge mobility.

Herein, Cs0.15FA0.85PbI2.85Br0.15 PSCs with different active layer thicknesses (350, 500 and 650 nm) have been characterized. In order to study device degradation, indoor cell lifetime testing was carried out according to the International Summit on OSC Stability (ISOS) standard L-1 protocol [3]. Devices show a dramatic burn-in degradation that increases with active layer thickness. After several minutes of continuous illumination, the efficiency of thinner and medium thickness devices stabilizes. However, thicker samples show no stabilization of the efficiency. In order to study in detail the dynamical processes occurring in the device, samples were also characterized using Impedance Spectroscopy (IS) at different degradation stages, and data were fitted to a three RC/RCPE circuit [4]. The low frequency capacitance in the thickest samples suffers a strong increase with time, which suggests a significant growth of the mobile ion population. This increase of the ion density partially screens the electric field, which yields a reduction of the extracted current and, consequently, the efficiency.


This work has been supported by Comunidad de Madrid under the SINFOTON2-CM Research Program (S2018/NMT-4326-SINFOTON2-CM) and the Spanish Ministry of Economy, the Agencia Estatal de Investigación and European Union’s FEDER under the TEC2016-77242-C3-3RnAEI/FEDER, UE Projects.

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