Pyridine-Terminated Conjugated Organic Molecules as an Interfacial Hole Transfer Bridge for NiO-Based Perovskite Solar Cells.

To engineer the NiO/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 and perovskite layers for NiO-based perovskite solar cells (PSCs). One terminal pyridine group interacts with the NiO layer, while the other one coordinates with the Pb atoms of the perovskite layer, erecting an interfacial hole transfer bridge between NiO and perovskite. Surface modification of the NiO film with the PTZ molecules is able to enhance hole extraction, increase hole mobility and conductivity of NiO, 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 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.