Highly reproducible, efficient hysteresis-less CH3NH3PbI3-xClx planar hybrid solar cells without requiring heat-treatment

CH3NH3PbI3-xClx(MAPbI(3)-Cl-x(x)) mixed halide perovskite powder with uniform composition was synthesized via simple solution chemistry, which demonstrates highly reproducible, efficient planar type MAPbI(3-x)Cl(x) mixed halide perovskite solar cells. Pure MAPbI(3-x)Cl(x) mixed halide perovskite powder was synthesized by reacting a 3 : 1 molar ratio of MAI : PbCl2 powder mixture in isopropanol (IPA) solution for 30 min at 60 degrees C with subsequent repeated centrifugation and washing in IPA. IPA functions as both the reaction medium for the formation of MAPbI(3-x)Cl(x) mixed halide and a selective remover of unreacted MAI and MACl byproducts. Accordingly, we could deposit a pinhole-free dense MAPbI(3-x)Cl(x) mixed halide perovskite film on a TiO2/FTO substrate through a simple one step spin-coating of pure MAPbI(3-x)Cl(x) mixed halide perovskite powder in DMF solution with HI additive, without further long heat-treatment processes. The deposited MAPbI(3-x)Cl(x) mixed halide perovskite film revealed uniform composition throughout the entire area, and the ratio of Cl to I + Cl and I + Cl to Pb was constant at similar to 0.03 and similar to 1/3, respectively. On the other hand, the conventional MAPbI(3-x)Cl(x) mixed halide perovskite film prepared by the long heat-treatment process had non-uniform composition because the ratio of Cl to I + Cl fluctuated greatly from 0 to 7.2. The average efficiency of planar type MAPbI(3-x)Cl(x) mixed halide perovskite solar cells was 18.65% +/- 0.30% and the champion cell had 1.11 V V-oc, 22.1 mA cm(-2) J(sc), 77% F.F., and 18.9% eta for forward scan conditions and 1.11 V V-oc, 22.1 mA cm(-2) J(sc), 78% F. F., and 19.1%. for reverse scan conditions. Although the thickness of the MAPbI(3-x)Cl(x) mixed halide perovskite layer varied from similar to 500 nm to similar to 900 nm, the efficiency was within the range of 18.3%-19.0%.