Reducing　the　dark　current　of　photodetectors　is　an　important　strategy　for　enhancing　the　detection　sensitivity,　but　hampered　by　the　manufacturing　cost　due　to　the　need　for　controlling　the　complex　material　composition　and　processing　intricate　interface.　This　study　reports　a　new　single-component　photochromic　semiconductor,　[(HDMA)4(Pb3Br10)(PhSQ)2]n　(1,　HDMA　=　dimethylamine　cation,　PhSQ　=　1-(4-sulfophenyl)-4,4＇-bipyridinium),　by　introducing　a　redox-active　monosubstituted　viologen　zwitterion　into　inorganic　semiconducting　skeleton.　It　features　yellow　to　green　coloration　after　UV　irradiation　with　the　sharply　dropping　intrinsic　conductivity　of　14.6-fold,　and　the　photodetection　detection　sensitivity　gain　successfully　doubles.　The　reason　of　decreasing　conductivity　originates　from　the　increasing　the　band　gap　of　the　inorganic　semiconducting　component　and　formation　of　Frenkel　excitons　with　strong　Coulomb　interactions,　thereby　decreasing　the　concentration　of　thermally　excited　intrinsic　carriers.　This　study　reports　a　new　photochromic　semiconductor　with　conductivity　dropping　sharply　by　14.6-fold　after　photochromism,　and　succeeds　in　realizing　photodetection　detection　sensitivity　gain　by　photoinduced　electron　transfer　strategy　for　the　first　time.image