Efficient interface engineering of N, N'-Dicyclohexylcarbodiimide for stable HTMs-free CsPbBr3 perovskite solar cells with 10.16%-efficiency

The back interface issues including numerous defects and imperfect contact, mismatched energy level are regarded as the key detrimental factors causing serious charge recombination and energy loss (Eloss) and inferior charge extraction to achieve high efficiency Hole transport materials-free (HTMs-free) carbon-based Perovskite solar cells (PSCs). To address this drawback, an effective interface engineering via depositing N, N'-Dicyclohexylcarbodiimide (DCC) at PVSK/Carbon back interface is creatively implemented to passivate CsPbBr3 surface defects through forming interaction between N atoms with lone pair electrons and uncoordinated ions (eg Pb2+ and Cs+ ions) to suppress the defect states induced non-radiative recombination and Eloss. Concurrently, the smoothness and valence band of PVSK film with DCC modification are increased to improve the contact and band alignment at back interface, respectively, remarkably accelerating hole extraction and transportation and also reducing Eloss as well as charge recombination. As a result, the comprehensive performance of DCC interface modified HTMs-free carbon-based CsPbBr3 PSCs is significantly enhanced, especially the champion efficiency boosts to 10.16% from 6.60% of the control PSC. Furthermore, owing to the enhanced hydrophobicity and decreased imperfections of PVSK film with DCC modification, the optimized device without any encapsulation displays an excellent long-term stability under 85% RH air condition at 85 °C over 1200 h.