Possibility of highly efficient 2D-3D perovskite/CIGS tandem solar cells with over 30% efficiency

Tandem photovoltaics consisting of a wide-bandgap top cell and a narrow-bandgap bottom cell have shown great potential to exceed current single-junction photovoltaics. To maximize the dual junction benefit, significant research is needed in selecting and optimizing the structure of both solar devices. This work reports the optimization of tandem solar cells with a CIGS solar cell as the bottom cell and a 2D-3D perovskite solar cell (PSC) as the top cell via numerical simulations using SCAPS-1D. The performances of the PSCs were optimized by varying the bandgaps of the 2D-3D perovskite and the thickness of the perovskite layer. The bottom p-CIGS/n-GaSe heterojunction solar cell was also optimized in terms of the thicknesses of the p-type/n-type layer and defect densities. The top PSC and bottom CIGS solar cells individually displayed maximum power conversion efficiencies (PCEs) of ∼21.41% and ∼12.98%, respectively. This simulation study was carried out for tandem solar cells by matching the optical behavior of the bottom cells with the calculated spectra of 2D-3D PSCs. Proper matching with CIGS cells in the tandem device was performed by varying the thickness of the perovskite layer with respect to different bandgaps. With the optimized 2D-3D perovskite/CIGS tandem device, over ∼30% PCE was recorded. To the best of our knowledge, this is the first time a 2D-3D perovskite solar cell/GIGS-GaSe heterojunction solar cell based tandem device has been optimized via numerical simulation. Based on our findings, a low-cost GIGS-GaSe heterojunction solar cell can be optimized as the bottom cell to fabricate efficient 2D-3D perovskite tandem solar cells.