We present a novel method to grow a uniform Cl-incorporated perovskite absorber layer using a mixed halide source by a modified two-step process.

The introduction of Cl into CH3NH3PbI3 precursors is reported to enhance the performance of CH3NH3PbI3 solar cell, which is attributed to the significantly increased diffusion lengths of carriers in CH3NH3Pb(I,Cl)3 solar cell. It has been assumed but never experimentally approved that the defect density in CH3NH3Pb(I,Cl)3 solar cell should be reduced according to the higher carrier lifetime observed from photoluminescence (PL) measurement. We have fabricated CH3NH3Pb(I,Cl)3 solar cell by adding a small amount of Cl source into CH3NH3PbI3 precursor. The performance of CH3NH3Pb(I,Cl)3 solar cell is significantly improved from 15.39% to 18.60%. Results from scanning electron microscopy and X-ray diffraction indicate that the morphologies and crystal structures of CH3NH3PbI3 and CH3NH3Pb(I,Cl)3 thin films remain unchanged. Open circuit voltage decay and admittance spectroscopy characterization jointly approve that Cl plays an extremely important role in suppressing the formation of defects in perovskite solar cells.

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Carbon nanotube (CNT) functionalized probes are expected to offer better resolution in Kelvin probe force microscopy (KPFM) but are suspected of lower sensitivity because of the small area between the CNT end and the sample surface. This paper quantitatively analyzes the resolution and sensitivity of KPFM using CNT functionalized probes. First, point spread functions (PSFs) of CNT functionalized probes are derived for both amplitude-modulation and frequency-modulation detection in KPFM. Based on these PSFs, the resolution and sensitivity of KPFM using CNT functionalized probes are analyzed. The findings suggest that CNT functionalized probes offer better resolution and are sensitive enough under proper operational conditions. These findings provide practical guidance for designing and making CNT functionalized probes in KPFM applications.