Design Strategy for Improving Optical and Electrical Properties and Stability of Lead-Halide Semiconductors

Broad absorption, long-lived photogenerated
carriers, high conductance,
and high stability are all required for a light absorber toward its
real application on solar cells. Inorganic–organic hybrid lead-halide
materials have shown tremendous potential for applications in solar
cells. This work offers a new design strategy to improve the absorption
range, conductance, photoconductance, and stability of these materials.
We synthesized a new photochromic lead-chloride semiconductor by incorporating
a photoactive viologen zwitterion into a lead-chloride system in the
coordinating mode. This semiconductor has a novel inorganic–organic
hybrid structure, where 1-D semiconducting inorganic lead-chloride
nanoribbons covalently bond to 1-D semiconducting organic π-aggregates.
It shows high stability against light, heat, and moisture. After photoinduced
electron transfer (PIET), it yields a long-lived charge-separated
state with a broad absorption band covering the 200–900 nm
region while increasing its conductance and photoconductance. This
work is the first to modify the photoconductance of semiconductors
by PIET. The observed increasing times of conductivity reached 3 orders
of magnitude, which represents a record for photoswitchable semiconductors.
The increasing photocurrent comes mainly from the semiconducting organic
π-aggregates, which indicates a chance to improve the photocurrent
by modifying the organic component. These findings contribute to the
exploration of light absorbers for solar cells.