Selectively patterned TiO₂ nanorods as electron transport pathway for high performance perovskite solar cells

Organic-inorganic hybrid perovskite solar cells (PSCs) are attracting tremendous attention for new-generation photovoltaic devices because of their excellent power conversion efficiency and simple fabrication process. One of the various approaches to increase the efficiency of PSCs is to change the material or structure of the carrier transport layer. Here, optically long and electrically short structural concept is proposed to enhance the characteristics of a PSC by employing selectively grown single crystalline TiO₂ nanorods. The approach has the merit of increasing the electron-hole separation effectively and enables a thicker active layer to be coated without electrical loss by using TiO₂ nanorods as an electron pathway. Moreover, selectively grown TiO₂ nanorods increase the optical path of the incident light via scattering effects and enable a smooth coating of the active layer. Nanoimprint lithography and hydrothermal growth were employed to fabricate selectively grown TiO₂ nanorod substrates. The fabricated solar cell exhibits an efficiency of 19.86% with a current density, open-circuit voltage, and fill factor of 23.13 mA/cm², 1.120 V, and 76.69%, respectively. Time-resolved photoluminescence, ultraviolet-visible (UV-Vis) spectroscopy, and the incident photon to current efficiency (IPCE) analysis were conducted to understand the factors responsible for the improvement in characteristics of the fabricated PSCs.