Going Beyond Shockley-Queisser Limit Perovskite Chalcogenides Tandem Solar Cell

The efficiencies of single junction solar cell (SJ SC) technologies like silicon and cadmium telluride have been rapidly increasing and are nearing their fundamental Shockley Queisser (SQ) efficiency limit. New novel methods must be developed to go beyond the limitations of SJ SCs. A promising approach is the combination of an efficient narrow bandgap (NBG) absorber with a wide bandgap (WBG) absorber to form a tandem solar cell that can effectively utilize the solar spectrum. The aim of this work is the realization of mechanically stacked perovskite-antimony selenide (Sb2Se3) and perovskite-cadmium telluride (CdTe) 4T tandem solar cells. Perovskite materials with their excellent performance and tunable bandgap make it an ideal candidate for tandem solar cells. Sb2Se3 with a bandgap of 1.2eV and a theoretical efficiency limit of over 30% and CdTe with a bandgap of 1.5eV and an efficiency over 22% make them potential NBG absorbers. In this work, we first simulated 4T tandem cells pairing a 1.6eV WBG Perovskite solar cell (PSC) with a 1.2 eV NBG Sb2Se3 cell and a 1.6eV WBG PSC with a 1.5 eV NBG CdTe cell using Solar Cell Capacitance Simulator (SCAPS). We obtained a simulated tandem PCE of 23.14 % for the perovskite Sb2Se3 tandem and a PCE of 23.37% for the perovskite CdTe tandem. We then developed two WBG perovskite top cells with a bandgap of 1.6eV and 1.77eV to study the impact of bandgap on the tandem architecture. We also developed a CdTe solar cell with Cu doping which had a PCE of 17.94% and a Sb2Se3 solar cell with a PCE of 5.76%. As a substitute for the opaque metal back electrode for the top cell, we developed an indium tin oxide (ITO) transparent electrode using DC sputtering to fabricate a semitransparent top cell. By mechanically stacking the sub-cells, we obtained an excellent 4T tandem PCE of 16.13% for the perovskite-Sb2Se3 tandem and a tandem PCE of 19.41% for the perovskite-CdTe tandem. The experimental results show promising tandem cell performance and pave the way to go beyond the SQ limit.