© 2020 Elsevier GmbHIntermediate-band solar cells, IBSCs, with single IB provide better utilization of the solar spectrum than single junction solar cells. In this study, Model−B IBSC was proposed, investigated and compared with previously used two models named here as Model−A and Model−C respectively. Detailed Balance Model was applied to satisfy Current Balance Equations with the optimum photo filling of IB states in Model−B. Optimum design parameters were obtained using 104 cm−1 of band-to-band absorption coefficient, α, in the wide range of band gap materials, overlapping absorption, photo filling, f, of IB states, capture cross-section ratio of carriers, concentration of IB states, and IB layer thickness, w, under 1–46,000 sun concentration, X. Maximum limiting efficiency value of 63.2% has been obtained with 1.95 eV of band gap, for fαw≥5 and 46,000X, under non-overlapping absorption. The peak efficiency of Model−B was 16% over the Model−A and 8% over the Model−C, for equal capture cross sections under large overlapping. The peak efficiency of Model−B was 35% over Model−A, at large non-equal capture cross-sections and large overlapping. Results predicted that the materials in the wide range of band gaps could be good candidates for fabricating IBSCs using Model−B with an efficiency of 50% or above at lower sun concentration, 10,000X, even under large overlapping.