A monolithic all-perovskite tandem solar cell with 2-T, 3-T and 4-T architecture integrated

Multi-junction all-perovskite tandem solar cells (A-PTSCs) can achieve higher power conversion efficiency (PCE) value beyond the Shockley-Queisser limit of single-junction perovskite solar cells (PSCs). However, only one side of the substrate is used in traditional two-junction tandem devices architecture, so that two-terminal (2-T) tandem devices require the preparation of a high quality and complex interconnection layer (ICL) to connect the two sub-cells and four-terminal (4-T) tandem devices require two substrates for two sub-cells. Here we demonstrate a two-junction A-PTSC using a double-sided ITO (D-ITO) glass substrate. The wide bandgap (W-Eg) perovskite (1.75 eV) as the upper cell and the narrow bandgap (N-Eg) perovskite (1.21 eV) as the bottom cell are deposited on both side of the D-ITO substrate, respectively. By changing the wiring method, on a substrate, 2-T, three-terminal (3-T), and 4-T integrated A-PTSC are obtained with efficiencies of 21.17% for 2-T tandem architecture, 17.71% for 3-T and 21.55% for 4-T. The concept and design here represent a new architecture toward A-PTSCs.