Efficient Organic Tandem Solar Cells Enabled by Solution-Processed Interconnection Layer and Fine-Tuned Active Layer

Organic tandem solar cells (OTSCs) with the merits of overcoming the S-Q limit of single-junction, enhancing and expanding the sunlight harvesting, and minimizing the thermalization energy loss, provide a practical strategy to break through the power conversion efficiency (PCE). However, it is still challenge to realize the multilayered structure by all-solution processing, especially shortage of interconnection layer (ICL), which physically and electronically connects front and rear subcells to accomplish the complicated tandem structure. Herein, all-solution-processed ICL of modified poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (m-PEDOT) and titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) is invented for constructing inverted OTSCs, and by systematically managing the light and carriers within the stacked multilayers, highly efficient OTSCs are demonstrated. Compared with the traditional ICLs, it avoids the complicated vacuum evaporation and synthesis processes, guaranteeing low cost and high reproducibility. Furthermore, m-PEDOT/TIPD ICL demonstrates excellent solvent resistance, high transmittance, and good conductivity. To enhance the light harvesting, absorption complementary donors and acceptors are selected as photoactive materials in front and rear subcells, and the transfer matrix formalism optical modeling is introduced to achieve the balanced short-circuit current density of each subcell in OTSCs. By systematic device optimizations, the best PCE of 15.26% is achieved, among the best results reported for OTSCs.