Perovskite/CIGS Tandem Solar Cells: From Certified 24.2% toward 30% and Beyond

We demonstrate a monolithic perovskite/CIGS tandem solar cell with acertified power conversion efficiency (PCE) of 24.2%. The tandem solar cell still exhibitsphotocurrent mismatch between the subcells; thus optical simulations are used todetermine the optimal device stack. Results reveal a high optical potential with theoptimized device reaching a short-circuit current density of 19.9 mA cm-2and 32% PCEbased on semiempirical material properties. To evaluate its energy yield, wefirstdetermine the CIGS temperature coefficient, which is at-0.38% K-1notably higherthan the one from the perovskite subcell (-0.22% K-1), favoring perovskite in thefieldoperation at elevated cell temperatures. Both single-junction cells, however, aresignificantly outperformed by the combined tandem device. The enhancement in energyoutput is more than 50% in the case of CIGS single-junction device. The resultsdemonstrate the high potential of perovskite/CIGS tandem solar cells, for which wedescribe optical guidelines toward 30% PCE