Investigation on structures, band gaps, and electronic structures of lead free La2NiMnO6 double perovskite materials for potential application of solar cell

•Lead-free La2NiMnO6 are first studied for application on perovskite solar cell.•Electronic structures of monoclinic and rhombohedral La2NiMnO6 is very similar.•Monoclinic La2NiMnO6 is a better candidate than rhombohedral one for solar cell.

Lead free double perovskites La2NiMnO6 were first studied for potential application on solar cells. The rhombohedral and the monoclinic La2NiMnO6, with B-site of Ni3+/Mn3+, were respectively formed under different synthesizing conditions. The experimental results show that the monoclinic La2NiMnO6 sample has a band gap of 1.4 eV and valence band of −5.8 eV, on the other hand, the respective values for rhombohedral sample are 1.2 eV and −5.7 eV. The density function theory calculation demonstrates that the calculated band gap for the monoclinic La2NiMnO6 is larger than that for the rhombohedral one. However, the electronic structures for these La2NiMnO6 are found very similar to each other. Our combined experimental and theoretical studies indicate that, from the aspects of band gaps and energy levels, double perovskite La2NiMnO6 of monoclinic phase could be a better candidate than that of rhombohedral phase for light harvesting.