Smart　windows　with　adjustable　transmittance　via　physical　stimuli　are　eagerly　desired　for　sorts　of　energy-saving　lighting　systems.　However,　reciprocal　trade-off　relationship　such　as　high　transparency　and　coloration/discoloration　ability　exists　in　smart　windows,　not　conducive　to　optical-electrical　coupling　and　leap　in　performance.　Substituting　for　common　composites　utilized　in　smart　windows,　here,　single　transparent　ceramic-based　smart　windows　are　reported　through　composition　design　and　defect　management　strategies　to　regulate　the　optoelectronic　performances　and　break　off　the　contradictions　between　optical　transmittance,　photo-thermochromism　and　electrical　conductivity.　By　first　principles　calculations　and　precisely　tuning　Er3+,　Ba2+,　Sr2+　concentrations　in　non-stoichiometric　Er-doped　(K0.5Na0.5)NbO3-(Ba,　Sr)TiO3,　the　fabricated　ceramics　exhibit　brilliant　transparency　and　multi-mode　dramatical　and　reversible　modulations　of　pellucidity,　photoluminescence　intensity,　along　with　conductivity　(over　fivefold　variation),　enabling　prominent　optoelectronic　information　storage　and　modulating　capacity　in　vivid　potential　applications,　such　as　easy-readout/erasable　optical　memorizers,　photo-memristors　and　anti-counterfeiting　displays.