  A modified detailed balance model is built to understand and quantify
efficiency loss of perovskite solar cells. The modified model captures the
light-absorption dependent short-circuit current, contact and transport-layer
modified carrier transport, as well as recombination and photon-recycling
influenced open-circuit voltage. Our theoretical and experimental results show
that for experimentally optimized perovskite solar cells with the power
conversion efficiency of 19%, optical loss of 25%, non-radiative recombination
loss of 35%, and ohmic loss of 35% are the three dominant loss factors for
approaching the 31% efficiency limit of perovskite solar cells. We also find
that the optical loss will climb up to 40% for a thin-active-layer design.
Moreover, a misconfigured transport layer will introduce above 15% of energy
loss. Finally, the perovskite-interface induced surface recombination, ohmic
loss, and current leakage should be further reduced to upgrade device
efficiency and eliminate hysteresis effect. The work contributes to fundamental
understanding of device physics of perovskite solar cells. The developed model
offers a systematic design and analysis tool to photovoltaic science and
technology.
