Pyridine-Terminated Conjugated Organic Molecules as an Interfacial Hole Transfer Bridge for NiO_<i>x</i>-Based Perovskite Solar Cells

Abstract

To engineer the NiO_<i>x</i>/perovskite interface and promote interfacial hole transfer, two pyridine-terminated conjugated small organic molecules (PTZ-1 and PTZ-2) are synthesized to link the NiO_<i>x</i> and perovskite layers for NiO_<i>x</i>-based perovskite solar cells (PSCs). One terminal pyridine group interacts with the NiO_<i>x</i> layer, while the other one coordinates with the Pb atoms of the perovskite layer, erecting an interfacial hole transfer bridge between NiO_<i>x</i> and perovskite. Surface modification of the NiO_<i>x</i> film with the PTZ molecules is able to enhance hole extraction, increase hole mobility and conductivity of NiO_<i>x</i>, reduce defect density, and retard interfacial charge recombination. As a consequence, power conversion efficiency is improved from 12.53 to 16.25 and 17.00% upon surface modifications of NiO_<i>x</i> with PTZ-1 and PTZ-2, respectively. Furthermore, the modified PSCs exhibit almost no hysteresis and show good stability after storage in air (relative humidity of 30-40%) for 500 h without encapsulation.