Performance improvement of inverted perovskite solar cells using TiO₂ nanorod array and mesoporous structure

In view of the low carrier mobility of organic materials, the carrier collection ability was suffered from the short transport length before carriers were recombined. To improve performances by enhancing carrier collection ability, the optimal period was 1.5 μm which was obtained by changing the period of titanium dioxide (TiO₂) nanorod array in the inverted perovskite solar cells (IPSCs). The power conversion efficiency was improved to 11.96% from the 7.66% of the standard planar IPSCs. Besides, due to the inherent properties of high absorption surface area and high light scattering ability, the 150-nm-thick TiO₂ mesoporous layer was embedded in the TiO₂ electron transport layer. By changing the annealing temperature, the optimal crystallinity of anatase phase and the optimal porous distribution were obtained in the TiO₂ mesoporous layers annealed at 500 °C for 30 min. Using the optimal annealed TiO₂ mesoporous layers in the IPSCs, the power conversion efficiency was improved to 12.73%. The power conversion efficiency of 14.47% was obtained for the IPSCs embedded with the optimal 1.5-μm-periodic TiO₂ nanorod array and the optimal 500 °C-annealed TiO₂ mesoporous layer in the electron transport layer, simultaneously.