Ideal Bandgap Organic-Inorganic Hybrid Perovskite Solar Cells.

Extremely high power conversion efficiencies (PCEs) of ≈20-22% are realized through intensive research and development of 1.5-1.6 eV bandgap perovskite absorbers. However, development of ideal bandgap (1.3-1.4 eV) absorbers is pivotal to further improve PCE of single junction perovskite solar cells (PVSCs) because of a better balance between absorption loss of sub-bandgap photons and thermalization loss of above-bandgap photons as demonstrated by the Shockley-Queisser detailed balanced calculation. Ideal bandgap PVSCs are currently hindered by the poor optoelectronic quality of perovskite absorbers and their PCEs have stagnated at <15%. In this work, through systematic photoluminescence and photovoltaic analysis, a new ideal bandgap (1.35 eV) absorber composition (MAPb0.5 Sn0.5 (I0.8 Br0.2 )3 ) is rationally designed and developed, which possesses lower nonradiative recombination states, band edge disorder, and Urbach energy coupled with a higher absorption coefficient, which yields a reduced Voc,loss (0.45 V) and improved PCE (as high as 17.63%) for the derived PVSCs. This work provides a promising platform for unleashing the complete potential of ideal bandgap PVSCs and prospects for further improvement.