2 research outputs found
Charge Carrier Trapping at Surface Defects of Perovskite Solar Cell Absorbers: A First-Principles Study
The
trapping of charge carriers at defects on surfaces or grain
boundaries is detrimental for the performance of perovskite solar
cells (PSCs). For example, it is the main limiting factor for carrier
lifetime. Moreover, it causes hysteresis in the current–voltage
curves, which is considered to be a serious issue for PSCs’
operation. In this work, types of surface defects responsible for
carrier trapping are clarified by a comprehensive first-principles
investigation into surface defects of tetragonal CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPbI<sub>3</sub>). Considering defect formation
energetics, it is proposed that a Pb-rich condition is preferred to
an I-rich one; however, a moderate condition might possibly be the
best choice. Our result paves the way for improving the performance
of PSCs through a rational strategy of suppressing carrier trapping
at surface defects
Inorganic Lattice Fluctuation Induces Charge Separation in Lead Iodide Perovskites: Theoretical Insights
The
high performance of recently emerged lead halide perovskite
based photovoltaic devices has been attributed to remarkable carrier
properties in this kind of material: long carrier diffusion length,
long carrier lifetime, and low electron–hole recombination
rate. However, the charge separation mechanism underlying such carrier
properties is still debated in this research field. In this work,
using first-principles molecular dynamics simulations, we have demonstrated
that the charge separation is induced by the structural fluctuation
of the inorganic lattice, assuming that the charge carriers occupy
the band edge. It is shown that the charge separation is attributed
to the electrostatic potential fluctuation coupled to the inorganic
lattice dynamics, on the basis of both simple tight-binding-model-based
analyses and first-principles calculations. These results suggest
that the organic cations, which are often used as components of lead
halide perovskites, are unlikely to be essential for the above-mentioned
carrier properties. Hence, it is expected that all-inorganic lead
halide perovskite based photovoltaics might be able to rival organic–inorganic
lead halide perovskite based ones in performance