A novel convenient and efficient approach to produce CsSnI₃ QDs through a one-pot synthesis is employed to largely enhance the PCE of lead-free perovskite solar cells (PVSCs). The CsSnI₃ QD-based device has the maximum PCE of 5.03%, which is the highest performance for all-inorganic lead-free PVSCs reported so far.

The performance of perovskite solar cells is largely enhanced by modifying the energy match of electrodes with coupled 2D interfacial layers. The V_OC is about 0.17 V increased to 1.135 V and 1.176 V for the CH₃NH₃PbI₃ and CH₃NH₃PbI_2.5Br_0.5 based devices, respectively. The PCE of the PEDOT:PSS based p–i–n solar cells is up to 19.14%.