High‐Efficiency Perovskite/PbS Quantum Dot Tandem Solar Cells With Tailored Hole Transport Layer Selection via Simulations and Experiments

Perovskite and PbS quantum dots (QDs) tandem solar cells demonstrate significant advantages in surpassing the efficiency limits of single‐junction devices due to the spectral complementarity between the wide bandgap (≈1.55 eV) perovskite top cell and the narrow (≈0.95 eV) PbS QDs bandgap bottom cell. However, the hole transport layer of the perovskite top solar cell is a challenge for the tandem solar cells, resulting in the performance still lagging. Herein, the effects of two types of hole transport layers (HTLs), Spiro‐OMeTAD, and NiO X , on the performance of four‐terminal (4‐T) and two‐terminal (2‐T) tandem solar cells are systematically investigated through the 1D Solar Cell Capacitance Simulator simulation. For 4‐T tandem solar cells, simulations predict that a device using Spiro‐OMeTAD can achieve an efficiency of 27.03%, whereas one using NiO X can reach 24.56%. In addition, in the 2‐T tandem device, the efficiencies of the two devices are 24.17% and 23.38%, respectively. Based on the simulation results, the corresponding 4‐T and 2‐T tandem devices are fabricated with efficiencies of 27.05% and 17.11%, respectively. Thus, these findings will accelerate the optimization of the performance of perovskite and PbS QDs tandem solar cells approaching their theoretical efficiency limit.