Recently,　hybrid　improper　ferroelectricity　in　layered　perovskites　is　becoming　an　effective　way　to　expand　the　compositional　palette　to　find　new　ferroelectrics.　In　the　present　work,　the　ground　state,　electronic　structure,　optical　properties,　effective　carrier　masses,　ferroelectric　polarization,　and　polarization　switching　pathways　of　the　Ruddlesden-Popper　perovskite　chalcogenides　Sr3B2X7　(B　=　Ti,　Zr,　Hf;　X　=　S,　Se)　were　thoroughly　investigated　by　first-principles　calculations.　Some　new　hybrid　improper　ferroelectrics　with　the　A2(1)am　polar　ground　state,　i.e.,　Sr3Zr2S7,　Sr3Zr2Se7,　Sr3Hf2S7,　and　Sr3Hf2Se7,　were　predicted　by　confirming　the　electric　polarization　induced　from　a　trilinear　coupling　of　octahedral　rotation　and　tilting　modes.　The　results　showed　that　the　ferroelectric　photovoltaic-related　properties　such　as　band　gaps　and　electric　polarizations　depend　crucially　on　the　amplitude　of　octahedral　rotations　and　tilts　of　perovskite　blocks.　It　was　predicted　that　Sr3Zr2Se7　could　be　a　good　candidate　for　ferroelectric　photovoltaic　device　applications　by　a　systematical　evaluation　of　ferroelectric　photovoltaic　properties　of　all　hypothetical　compounds.