Tuning the buried interface with d-sorbitol-modified mixed SAMs for high-efficiency inverted perovskite solar cells.

One of the key bottlenecks limiting high efficiency and long-term stability in perovskite solar cells (PSCs) is non-radiative recombination and slow interfacial-process-related losses at the buried transparent conducting oxide/perovskite interface. Here, a mixed 2PACz/MeO-2PACz self-assembled monolayer (SAM) (1 : 3, w/w) is deposited on high-haze FTO to form a hole-selective contact in an inverted (p-i-n) architecture, and the buried interface is further modified with d-sorbitol (DS), a polyol bearing multiple -OH groups. X-ray diffraction confirms that mixed-SAM formation and DS treatment preserve the perovskite crystal structure without detectable secondary phases, while sharpening diffraction features consistent with more controlled crystallization. The mixed-SAM enables smoother perovskite growth, and DS treatment preserves this smooth morphology while increasing surface wettability. Steady-state photoluminescence increases and time-resolved PL exhibits prolonged decay components after DS treatment, consistent with reduced non-radiative recombination losses associated with the buried interface. Electrochemical impedance spectroscopy shows an increased recombination resistance (