  With the consideration of photon recycling effect, the efficiency limit of
methylammonium lead iodide (CH3NH3PbI3) perovskite solar cells is predicted by
a detailed balance model. To obtain convincing predictions, both AM 1.5
spectrum of Sun and experimentally measured complex refractive index of
perovskite material are employed in the detailed balance model. The roles of
light trapping and angular restriction in improving the maximal output power of
thin-film perovskite solar cells are also clarified. The efficiency limit of
perovskite cells (without the angular restriction) is about 31%, which
approaches to Shockley-Queisser limit (33%) achievable by gallium arsenide
(GaAs) cells. Moreover, the Shockley-Queisser limit could be reached with a 200
nm-thick perovskite solar cell, through integrating a wavelength-dependent
angular-restriction design with a textured light-trapping structure.
Additionally, the influence of the trap-assisted nonradiative recombination on
the device efficiency is investigated. The work is fundamentally important to
high-performance perovskite photovoltaics.
