posted on 2020-06-05, 15:36authored byZhe Sun, Yanan Kang, Guoguo Wang, Mao Liang, Song Xue
The mismatch of the
energy level between the electron transport
layer (ETL) and the perovskite (PS) film is one of the origins of
current–voltage (J–V) hysteresis in perovskite solar cells (PSCs). Drift-diffusion simulations
are conducted to explain how the band alignment affects the charge
extraction across the ETL/PS interface, and hence varies the responses
of photocurrent. Our simulations show that the band alignment has
a profound influence on the evolution of the profiles of movable ions
during voltage scan. The band mismatch at the ETL/PS interface is
shown to engender the accumulation of movable anions and give rise
to severe J–V hysteresis.
We further demonstrate that a rational design on the energy alignment
of PSCs is vital to reduce the hysteresis no matter if charge loss
in PSCs is determined by bulk recombination or trap-assisted surface
recombination. Moreover, the PSCs suffering from interface band mismatch
are found to exhibit various hysteresis behaviors depending on the
rate of voltage scan. It implies that the voltage scan at different
speeds could be helpful to diagnose the problem of PSCs.