If the semiconductor substance is translucent, the light might be emitted through the junction as junction functions since the source of light. LED is operated in forward biased mode only. If it will eventually work in reverse biased it will get problems as it are unable to with stand reverse https://www.uk-exhibitionstands.co.uk/product/casonara-blimp-rectangle-360o-hanging-light-box-display-300m/