Revisiting the Shockley–Queisser Limit: Understanding Solar Cell Efficiency in One Sun and Indoor Environments

junction as a blackbody (BB) illuminated by the sun as a BB, remains a theoretical benchmark but overlooks key loss mechanisms like nonradiative recombination. By reproducing the SQL and incorporating the external radiative efficiency (ERE), we quantify real-world efficiency losses. Our findings show that GaAs and perovskite solar cells, with minimal nonradiative losses, approach theoretical limits under both AM1.5G and indoor lighting. We also demonstrate that BB intensity─modulated by temperature or geometric factors─shifts optimal efficiency: lower BB temperatures cause a red shift, while reduced geometric factors induce a blue shift. Among artificial sources, LEDs and fluorescents offer the best performance at higher energies, whereas incandescent light favors lower energies. These results highlight the need to minimize nonradiative losses and tailor device design to specific spectral irradiance.