23.6 % Efficient perovskite-organic tandem photovoltaics enabled by recombination layer engineering

Recombination layers are crucial in achieving high power conversion efficiency (PCE) in tandem solar cells. Here, we report the development and optimization of recombination junctions for high PCE perovskite-organic tandem solar cells (PO-TSCs). We choose a wide bandgap perovskite (1.79 eV) for the front subcell and a narrow bandgap (1.36 eV) organic bulk heterojunction (BHJ) for the rear subcell. The optimal thicknesses of the perovskite and organic layers were determined to be 260 and 100 nm, respectively, based on the analysis of Transfer-Matrix optical simulations. Our results demonstrate that the optimal recombination layer consists of an ultrathin layer of indium zinc oxide IZO (∼ 2 nm) deposited on MoO_x/2PACz, which delivers a PCE of 23.6 %. This high PCE is attributed to the high transparency of the recombination layer in the NIR spectra region and the low sheet resistance of IZO. Furthermore, we provide a theoretical analysis of the potential efficiency of PO-TSCs as a function of front and rear subcells and predict a maximum theoretical PCE value of more than 36 %. Our work highlights the importance of selecting the proper recombination layer design for achieving high-performance PO-TSCs.