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

To engineer the NiOx/perovskite interface and promote interfacial hole transfer, two pyridine-terminated conjugated small organic molecules (PTZ-1 and PTZ-2) are synthesized to link the NiOx and perovskite layers for NiOx-based perovskite solar cells (PSCs). One terminal pyridine group interacts with the NiOx layer, while the other one coordinates with the Pb atoms of the perovskite layer, erecting an interfacial hole transfer bridge between NiOx and perovskite. Surface modification of the NiOx film with the PTZ molecules is able to enhance hole extraction, increase hole mobility and conductivity of NiOx, 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 NiOx 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.