New Antimony-Based Organic–Inorganic Hybrid Material as Electron Extraction Layer for Efficient and Stable Polymer Solar Cells

Hybrid organic–inorganic materials are a new class
of materials used as interfacial layers (ILs) in polymer solar cells
(PSCs). A hybrid material, composed of antimony as the inorganic part
and diaminopyridine as the organic part, is synthesized and described
as a new material for application as the electron extraction layer
(EEL) in PSCs and compared to the recently demonstrated hybrid materials
using bismuth instead of antimony. The hybrid compound is solution-processed
onto the photoactive layer based on a classical blend, which is composed
of a PTB7-Th low band gap polymer as the donor mixed with PC70BM fullerene as the acceptor material. By using a regular device
structure and an aluminum cathode, the solar cells exhibited a power
conversion efficiency of 8.42%, equivalent to the reference device
using ZnO nanocrystals as the IL, and strongly improved compared to
the bismuth-based hybrid material. The processing of extraction layers
up to a thickness of 80 nm of such hybrid material reveals that the
change from bismuth to antimony has strongly improved the charge extraction
and transport properties of the hybrid materials. Interestingly, nanocomposites
made of the hybrid material mixed with ZnO nanocrystals in a 1:1 ratio
further improved the electronic properties of the extraction layers,
leading to a power conversion efficiency of 9.74%. This was addressed
to a more closely packed morphology of the hybrid layer, leading to
further improved electron extraction. It is important to note that
these hybrid EELs, both pure and ZnO-doped, also greatly improved
the stability of solar cells, both under dark storage in air and under
lighting under an inert atmosphere compared to solar cells treated
with ZnO intermediate layers.