<p>Multi-band semiconductors are promising candidates for high-efficiency photovoltaic devices. Various technological methodologies have been explored and put into practice. However, the efficiencies achieved experimentally fall short of expectations. In this study, considering the relative scale of all inter-band absorption coefficients, it has been determined that the anticipated efficiencies are difficult to attain. Furthermore, with all the results and considering the mathematical and boundary properties, a fit as a function of the absorptivities for efficiencies and energies of all examined multi-band solar cell types has been obtained.</p> Graphical abstract <p></p>