Constructing Robust Top Heterointerface with Quinoid Polymer for High Performance CsPbI3 Solar Cells

The excellent light absorption and nonvolatilization nature of triiodide cesium lead (CsPbI3) make it a promising candidate for high-performance photovoltaics, but the efficiency of CsPbI3 photovoltaics is still limited by severe open-circuit voltage (VOC) loss caused by nonradiative recombination. Herein, a quinoid polymer (named PAQM-TPD) is used as a dual-functional buffer layer to optimize the interface between the perovskite and the hole transport layer for reducing the VOC loss and broadening the light response in CsPbI3 perovskite solar cells (PSCs). Introducing PAQM-TPD induces Lewis acid–base interactions with CsPbI3 to form a stable heterointerface on top of the CsPbI3 crystal, which can passivate defects and extend the spectral response range. In addition, PAQM-TPD featuring high mobility and matching energy-level alignment generated by the CsPbI3/PAQM-TPD heterointerface provides a good driving force for hole transport, reducing the energy loss at the interface. Consequently, the comprehensive interface optimization results in the β-CsPbI3 PSCs achieving an efficiency of 19.98% and the highest current density (20.98 mA cm–2), with a low energy loss of 0.496 eV. Long alkyl side chains in the quinoid polymer also prevent water ingress and stabilize the perovskite heterointerface. Devices treated with PAQM-TPD retained 91% of their initial efficiency after 720 h of storage in an ambient air environment.