Effects of complexing agent on carrier transport property and photovoltaic performance of TiO2@MAPbI3 core-shell structured nanowire arrays

The excellent properties of nanowire arrays are retained in the shell-core structured nanowire arrays, and the contact area between the core and shell is increased. However, perovskite layers are prone to a variety of defects during the covering process. A large number of explorations for perovskite interfacial defects have revealed that the use of complexing agents to modify the surface of the transport layer can eliminate or ameliorate these defects. Potassium sodium tartrate (PSTA) and ethylenediaminetetraacetic acid (EDTA) are commonly used complexing agents because of their strong complexing ability and stable nature. In this paper, the photovoltaic performance of perovskite solar cells was improved by modifying TiO2 core nanowire arrays with different complexing agents. When TiO2 was modified by PTSA and EDTA, the PCE of the devices reached 8.23 % and 8.76 %, respectively, which is 14.5 % and 21.8 % higher than that of the unmodified device (7.19 %). The complexing agent modification resulted in a higher degree of crystallization, larger grain size, and higher light absorption of the light-absorbing layer. As EDTA has a strong complexing ability, it can form stable coordination bonds with uncoordinated ions, resulting in an effective reduction of defective states in the device, which is conducive to carrier extraction and collection. It is shown that the photovoltaic performance and the carrier transport property of shell-core structured nanowire arrays can be optimized by complexing agent modification, which will provide some guidance for improving the photovoltaic performance of core-shell structured solar cells.