Current prototypes of quantum-dot intermediate band solar cells suffer from voltage reduction due to the existence of thermal carrier escape. An enlarged subbandgap E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> would not only minimize this problem but would lead to a bandgap distribution that exploits more efficiently the solar spectrum. In this study, we demonstrate InAs/InGaP QD-IBSC prototypes with the following bandgap distribution: E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> = 1.88 eV, E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> = 1.26 eV, and E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> > 0.4 eV. We have measured, for the first time in this material, both the interband and intraband transitions by means of photocurrent experiments. The activation energy of the carrier thermal escape in our devices has also been measured. It is found that its value, compared with InAs/GaAs-based prototypes, does not follow the increase in E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> . The benefits of using thin-AlGaAs barriers before and after the quantum-dot layers are analyzed.