LONGi toasts new p-type TOPCon and commercial heterojunction cell efficiency records News Cell production at a LONGi facility. Image: LONGi. Solar cell efficiency records have continued to fall after LONGi toasted breakthroughs in both high-efficiency p-type solar cells and commercial heterojunction (HJ) cells. LONGi revealed today that its Cell R&D Center had achieved a new record cell efficiency of a p-type monocrystalline bifacial TOPCon solar cell of 25.02%, the first time a p-type cell had recorded a conversion efficiency in excess of 25%. The record was validated by the Institute for Solar Energy Research (ISFH) in Hamelin, Germany, which also confirmed LONGi’s record for its commercial-sized monocrystalline HJ solar cell produced by LONGi’s New Technology R&D Center.