I ' m happy I spent that night inside . <| sep |> Per unit weight , yes they weigh the same . But often in chemistry the weight isn ' t as important . The mass of a tin nucleus is just over half the mass of a lead nucleus so per unit weight , there are almost twice as many tin atoms as there are lead atoms . Or in other words , each perovskite unit cell will be the same size , but weigh much less . The volumetric energy will be comparable and the energy density of the tin cell would be much higher if the efficiency is the same , which it isn ' t because the tin perovskite efficiency is horrible . <| sep |> Sg might be my favorite anime but I can kind of agree . But ultimately the delivery was dramatically worse . And no one in rn is as awesome as okabe .