  Understanding and quantifying the main loss factors affecting the power
conversion efficiency of perovskite solar cells are urgently needed. In this
work, based on semiconductor physics, the expressions of bulk and surface
recombination currents are analytically derived. Then taking the optical loss,
series and shunt resistance losses, and bulk and surface recombination losses
into consideration, an equivalent circuit model is proposed to describe the
current density-voltage characteristics of practical perovskite solar cells.
Furthermore, by comparing to the drift-diffusion model, the pre-defined
physical parameters of the drift-diffusion model well agree with the fitting
parameters retrieved by the equivalent circuit model, which verifies the
reliability of the proposed model. Moreover, when the circuit model is applied
to analyze experimental results, the fitting outcomes show favorable
consistency to the physical investigations offered by the experiments. And the
relative fitting errors of the above cases are all less than 2%. Through
employing the model, the dominant recombination type is clearly identified and
split current density-voltage curves characterizing different loss mechanisms
are offered, which intuitively reveals the physical principles of efficiency
loss. Additionally, through calculating the efficiency loss ratios under the
open-circuit voltage condition, quantifying the above-mentioned loss mechanisms
becomes simple and compelling. Consequently, this model offers a guideline to
approach the efficiency limit from a circuit-level perspective. And the model
is a comprehensive simulation and analysis tool for understanding the device
physics of perovskite solar cells.
