Metal Nanoclusters as an Interfacial Modifier in Organic Solar Cells

Novel and diverse strategies are constantly under development to boost the efficiency and stability of organic solar cells (OSCs). Interface engineering involving various functional materials is currently a research focus because of its promising potential to enhance the device performance of OSCs^.1-3 Atomically precise metal nanoclusters, with tunable properties and notable dipole moments resulting from surface ligand interactions that provide stability to the nanoclusters, can be a promising candidate as an interfacial modifier.^{4, 5} Copper nanoclusters (Cu NCs), synthesized by a one-pot synthesis method, are shown to exhibit dipole moment and can cause work function modification on a surface. The novel approach of introducing Cu NCs as an interfacial modifier between the electron transporting layer and the active layer has yielded improved photovoltaic performance in both fullerene and non-fullerene based OSCs (PTB7-Th:PC₇₁BM and PM6:Y6 based OSCs). On insertion of Cu NCs, the best power conversion efficiency (PCE) obtained for the non-fullerene based system is 15.83% compared to that of 14.22% for the control device while the PCE enhanced from 7.79% to 8.62% for the fullerene based system. The interface modification has resulted in reduced recombination losses and charge accumulation at the interfaces. Impedance and transient measurements have also revealed efficient extraction of photogenerated charge carriers in Cu NC incorporated devices. The improved performance in Cu NC interfaced devices is attributed to work function modification, enabling reduced energy barrier and enhanced charge collection. Moreover, The Cu incorporated devices exhibit better operational stability under MPP tracking than the control device. This work demonstrates the potential of a new class of materials for interface modification and enhancing the performance of OSCs.<br/><br/><b>References</b><br/>1. D. Luo, W. Jang, D. D. Babu, M. S. Kim, D. H. Wang and A. K. K. Kyaw, Journal of Materials Chemistry A, 2022, 10, 3255-3295.<br/>2. L. Tian, Q. Xue, Z. Hu and F. Huang, Organic Electronics, 2021, 93, 106141.<br/>3. H. Tang, Y. Bai, H. Zhao, X. Qin, Z. Hu, C. Zhou, F. Huang and Y. Cao, Advanced Materials, 2023, n/a, 2212236.<br/>4. X. Liu and D. Astruc, Coordination Chemistry Reviews, 2018, 359, 112-126.<br/>5. Y. Zeng, S. Havenridge, M. Gharib, A. Baksi, K. L. D. M. Weerawardene, A. R. Ziefuß, C. Strelow, C. Rehbock, A. Mews, S. Barcikowski, M. M. Kappes, W. J. Parak, C. M. Aikens and I. Chakraborty, Journal of the American Chemical Society, 2021, 143, 9405-9414.