Strong absorption of (Mn 2 O 3 ) 3 CuSiO 3 with Jahn-Teller elongation and direct photothermal storage of (Mn 2 O 3 ) 3 CuSiO 3-Mg(OH) 2

To improve photon harvesting, we demonstrated that Jahn-Teller defects can efficiently reduce the band gap and increase the carrier density, which significantly intensify light harvesting and widen the absorption band. This may be an effective method for designing solar materials. The substitution of Mn 2 + with Jahn-Teller active Cu 2 + leads to quasi-metallic (Mn 2 O 3 ) 3 CuSiO 3 nanoparticles with a high concentration of charge carriers, displaying intense absorption in entire solar spectrum. Silicates may represent a new type of photon harvesting material. Mg(OH) 2 powder coated by Cu-braunite shows a 150 % increase in photothermal temperature, a tenfold improvement in photothermal-dehydration conversion and a 15.8-fold increase in the reversibility of 30 cycles of heat storage and release. This material may be practicable for directly harvesting solar energy and storing thermoenergy. Jahn-Teller effects are effective for tuning photon harvesting.