Tin-Lead Perovskite Solar Cells Featuring Buffer Layer Structures: A Combined Theoretical and Experimental Study

Abstract

Tin-lead (Sn-Pb) perovskite solar cells (PSCs) have received extensive attention due to their indispensable role in all-perovskite tandem solar cells. However, energy band matching between the absorber and charge transport layers remains challenging in terms of further improving efficiency of Sn-Pb PSCs. Herein, we investigate the role of a [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) buffer layer in optimizing energy level alignment for inverted Sn-Pb perovskite (FA 0.7 MA 0.3 Pb 0.5 Sn 0.5 I 3 ) photovoltaic devices using Solar Cell Capacitance Simulator simulations. The results prove that inserting PCBM between the perovskite and C 60 electron transport layer enhances power conversion efficiency of Sn-Pb PSC from 21.83% to 23.03%, due to the suppression of carrier recombination and an enhanced built-in electric field. The incorporation of PCBM induces the formation of a distinctive band structure within the device. This structure establishes an energy barrier that impedes hole transport while concurrently facilitating electron transport. Systematic parametric investigations demonstrate that modulating both the electron affinity of the PCBM interlayer and its donor doping concentration critically enhances photovoltaic performance by precisely tailoring the conduction band offset. Finally, devices with and without a PCBM buffer layer were fabricated. Experimental results consistently aligned with simulation-2 derived conclusions. This work provides a theoretical basis for designing efficient Sn-Pb PSCs through interfacial engineering.