Surface Modification with CuFeS2 Nanocrystals to Improve the Efficiency and Stability of Perovskite Solar Cells.

Poor stability retards the industrialization of perovskite solar cells (PSCs). One of the effective ways to solve this issue is to modify the perovskite surface to improve the efficiency and stability of the PSCs. Herein, we synthesized CuFeS2 nanocrystals and applied them to modify the perovskite surface. The efficiency of the PSCs with CuFeS2 modification is improved to 20.17% from 18.64% for the control devices. Some investigations demonstrate that the CuFeS2 modification passivates the perovskite surface defects and induces better energy band arrangement. Furthermore, the stability of the PSCs with CuFeS2 modification is improved compared with the devices without CuFeS2 modification. The efficiency of the PSCs with CuFeS2 modification maintains 93% of its initial value, whereas that of the devices without CuFeS2 modification decreases to 61% of the initial value. This work demonstrates that CuFeS2 is a novel material used as a modification layer to enhance the efficiency and stability of the PSCs.

Enhancement of Perovskite Solar Cells Efficiency using N-Doped TiO2 Nanorod Arrays as Electron Transfer Layer.

In this paper, N-doped TiO2 (N-TiO2) nanorod arrays were synthesized with hydrothermal method, and perovskite solar cells were fabricated using them as electron transfer layer. The solar cell performance was optimized by changing the N doping contents. The power conversion efficiency of solar cells based on N-TiO2 with the N doping content of 1% (N/Ti, atomic ratio) has been achieved 11.1%, which was 14.7% higher than that of solar cells based on un-doped TiO2. To get an insight into the improvement, some investigations were performed. The structure was examined with X-ray powder diffraction (XRD), and morphology was examined by scanning electron microscopy (SEM). Energy dispersive spectrometer (EDS) and Tauc plot spectra indicated the incorporation of N in TiO2 nanorods. Absorption spectra showed higher absorption of visible light for N-TiO2 than un-doped TiO2. The N doping reduced the energy band gap from 3.03 to 2.74 eV. The photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectra displayed the faster electron transfer from perovskite layer to N-TiO2 than to un-doped TiO2. Electrochemical impedance spectroscopy (EIS) showed the smaller resistance of device based on N-TiO2 than that on un-doped TiO2.