SnOx/carbon nanofibers enabling crystallization control and defect passivation for highly efficient air-processed PSCs

The enhancement in efficiency and stability of air-processed perovskite solar cells (PSCs) have garnered increasing attention. Carbon-based composite materials additives, due to their excellent electrical conductivity, outstanding stability and high flexibility, provide a novel idea for improving the performance of perovskite films as well as PSCs. In this study, the superfine SnO x /carbon composite nanofibers (SnO x /C NFs) with the average diameter of 26 nm was doped into perovskite films and modulating perovskite crystallization. The SnO x /C NFs provided a uniform heterogeneous nucleation site, regulate the crystal morphology of perovskite films via Sn-I coordination and O/(MA + , FA + ) electrostatic coupling, passivated the organic cations and Pb 2+ vacancy defects within the perovskite structure, and enhanced the overall quality of the films. The distinctive one-dimensional structure of SnO x /C NFs provides additional channels for charge transport, thereby facilitating more efficient charge extraction and effectively alleviating device defects. In addition, the flexible nanofibers released the residual stress and enhanced the stability of the devices. The power conversion efficiency (PCE) of the champion device with low hysteresis prepared under open-air conditions was 22.32 %. The champion device maintained initial PCE of 80.3 %, 90.6 % and 86.6 % under 55 ± 5 % RH for 1200 h, 85 °C for 500 h and AM 1.5 light illumination for 500 h, respectively. In addition, the SnO x /C NFs-based flexible-PSCs (f-PSCs) achieved a champion efficiency of 19.84 % and retained 92.13 % of their initial PCE after 300 cycles (radius = 7 mm).