Alcohol-based bifunctional ammonium cations, 2-hydroxyethylammonium (HEA + ), HO(CH 2 ) 2 NH 3 + , were introduced into formamidinium (FA + ) tin-based perovskites (HEA x FA 1-x SnI 3 ; x = 0-1) to absorb light in carbon-based mesoscopic solar cells. We found that HEA + cations play a key role to control the crystal structures, the lattice structures altered from orthorhombic (x = 0) to rhombohedral (x = 0.2-0.4) with greater symmetry. When x was increased to 0.6-1.0, tin and iodide vacancies were formed to generate 3D-vacant perovskites (HEA x FA 1-x Sn 0.67 I 2.33 , x ≥ 0.6) with a tetragonal structure. Tin-based perovskites in this series were fabricated into mesoporous solar cells using one-step drop-cast (DC), two-step solvent-extraction (SE), and SE + 3% ethylenediammonium diiodide (EDAI 2 ) as an additive. After optimization of device performance with the SE + 3% EDAI 2 approach, the HEA 0.4 FA 0.6 SnI 3 (HEAI = 40%) device gave the best photovoltaic performance with J SC = 18.52 mA cm -2 , V OC = 371 mV, FF = 0.562, and overall efficiency η = 3.9% after the device was stored for a period of 340 h.