Perovskite Solar Cells Employing a PbSO₄(PbO)₄ Quantum Dot-Doped Spiro-OMeTAD Hole Transport Layer with an Efficiency...

2,2',7,7'-Tetrakis(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-OMeTAD), the most widely used hole transport material in high-efficiency perovskite solar cells (PSCs), still has serious defects, such as moisture absorption and poor long-term conductivity, which seriously restrict further improvement of the power conversion efficiency (PCE) and stability of the cell. Herein, to overcome these problems, inorganic salt PbSO₄(PbO)₄ quantum dots (QDs) are incorporated into spiro-OMeTAD as the hole transport layer (HTL) for the first time. The incorporated PbSO₄(PbO)₄ QDs significantly hinder the agglomeration of lithium bis(trifluoromethanesulfonyl)-imide and improve the long-term conductivity through the oxidative interaction between PbSO₄(PbO)₄ QDs and spiro-OMeTAD and hydrophobicity of the HTL. Furthermore, the spiro-OMeTAD:PbSO₄(PbO)₄ composite film can effectively passivate perovskite defects at the perovskite/HTL interface, resulting in suppressed interfacial recombination. As a result, the PSC based on the spiro-OMeTAD:PbSO₄(PbO)₄ HTL shows an improved PCE of 22.66%, which is much higher than that (18.89%) of the control device. PbSO₄(PbO)₄ also significantly improves the moisture stability for 50 days at room temperature (at RH ∼ 40-50%) without encapsulation. This work indicates that inorganic PbSO₄(PbO)₄ QDs are crucial materials that can be employed as an additive in spiro-OMeTAD to enhance the efficiency and stability of PSCs.