Efficient inorganic CsPbI₂Br perovskite indoor photovoltaics demonstrated via slower crystallization by incorporated dimethylammonium iodide

Although inorganic CsPbI₂Br perovskite has an ideal bandgap for indoor photovoltaics (IPVs), its poor solubility causes rapid crystallization during spin-coating process and deteriorates the performance of IPVs. Here, efficient CsPbI₂Br IPVs are demonstrated through slower crystallization by introduction of dimethylammonium iodide (DMAI), which has better solubility in perovskite solvent compared to the inorganic CsPbI₂Br and is easily eliminated by thermal-annealing. Consequently, the incorporation of DMAI results in the CsPbI₂Br film with enlarged crystal grains with reduced interface traps. In addition, the incorporated DMAI orients preferentially the CsPbI₂Br crystals to expose (110) facet. Through controlling the amount of incorporated DMAI, eventually the CsPbI₂Br IPVs with 35.22% (0.096 cm²), 35.08% (1 cm²), and 29.80% (25 cm²) of power conversion efficiency under illumination of 1000 lux light-emitting diode lamp are achieved. The unencapsulated device has good long-term stability under 1000 lux lamp for 1000 h. (Figure presented.).