Tunable energy transfer in (Ba2−xSrx)Ca0.92Yb0.04Li0.04(Mo1−yWy)O6 with broadband sensitization and intense near-infrared emission

► Charge transfer state (CTS) of MoO6 can efficiently transfer energy to Yb3+ with 1000 nm near infrared (NIR) emission. ► The introduction of Sr2+ causes distortion of (Mo/Ca)O6 frameworks and results in more energy being transferred to Yb3+. ► Higher energy of CTS of WO6 prevents energy quenching among MoO6 groups, thus more energy is trapped by Yb3+. ► Underlying model for the tunable energy transfer of this series is proposed.