posted on 2021-04-22, 05:30authored byJingpeng Ren, Kaihua Ning, Haifen Liu, Zixuan Zhu, Weili Fan, Lixin Wang, Xiaohui Zhao, Shaopeng Yang
The
cathode interfacial layer plays a key role in enhancing the
efficiency and stability of organic solar cells. Constructing efficient
two-layer interfaces is one of the important strategies to improve
device performance. In this work, we deposited a thin layer of lithium
fluoride (LiF) beneath the electron transport layer poly[(9,9-bis(3′-((N,N-dimethyl)-N-ethylammonium)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)]dibromide (PFN-Br) and (N,N-dimethyl-ammonium N-oxide)propyl perylene diimide (PDINO), respectively, to prepare
conventional organic solar cells featuring a double electron transport
layer. The Voc and FF of the optimized
devices with a double electron transport layer were improved to achieve
a power conversion efficiency (PCE) of 16.4% for LiF/PFN-Br-based
devices and 16.0% for LiF/PDINO-based devices. The LiF-containing
double electron layers reduce the work function of the active layer,
makes electron injection more efficient, and promotes charge extraction
and collection. As an optical spacer layer, the thin layer of LiF
also changes the internal light intensity distribution, enabling the
active layer to absorb more photons and generate more excitons. In
addition to PCE enhancement, the LiF-containing double layers still
reduce photodegradation of the active layer and improve the stability
of the device.