Alumina Nanoparticle Interfacial Buffer Layer for Low‐Bandgap Lead‐Tin Perovskite Solar Cells

• Published in: Advanced functional materials 2023-08, Vol.33 (35), p.n/a
• Main Authors: Jin, Heon, Farrar, Michael D., Ball, James M., Dasgupta, Akash, Caprioglio, Pietro, Narayanan, Sudarshan, Oliver, Robert D. J., Rombach, Florine M., Putland, Benjamin W. J., Johnston, Michael B., Snaith, Henry J.
• Format: Article
• Language: English
• Subjects: Absorbers; Aluminum oxide; Buffer layers; Crystallization; Devices; Efficiency; Energy gap; Irradiance; Lead; lead‐tin; low‐bandgap; Materials science; methylammonium‐free; Nanoparticles; Perovskites; Photovoltaic cells; Service life assessment; shunt management; Solar cells; Stability; Thick films; Thickness; Tin
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202303012

Mixed lead‐tin (Pb:Sn) halide perovskites are promising absorbers with narrow‐bandgaps (1.25–1.4 eV) suitable for high‐efficiency all‐perovskite tandem solar cells. However, solution processing of optimally thick Pb:Sn perovskite films is notoriously difficult in comparison with their neat‐Pb counterparts. This is partly due to the rapid crystallization of Sn‐based perovskites, resulting in films that have a high degree of roughness. Rougher films are harder to coat conformally with subsequent layers using solution‐based processing techniques leading to contact between the absorber and the top metal electrode in completed devices, resulting in a loss of VOC, fill factor, efficiency, and stability. Herein, this study employs a non‐continuous layer of alumina nanoparticles distributed on the surface of rough Pb:Sn perovskite films. Using this approach, the conformality of the subsequent electron‐transport layer, which is only tens of nanometres in thickness is improved. The overall maximum‐power‐point‐tracked efficiency improves by 65% and the steady‐state VOC improves by 28%. Application of the alumina nanoparticles as an interfacial buffer layer also results in highly reproducible Pb:Sn solar cell devices while simultaneously improving device stability at 65 °C under full spectrum simulated solar irradiance. Aged devices show a six‐fold improvement in stability over pristine Pb:Sn devices, increasing their lifetime to 120 h. This Study uses a non‐continuous layer of alumina nanoparticles on the surface of rough Pb:Sn perovskite films, resulting in improved conformality of the subsequent electron transport layer. This leads to the alumina nanoparticle layer acting as an interfacial buffer layer between the rough absorber and top metal electrodes and hinders unwanted direct contact between them.