Effect of Interfacial Molecular Carboxylate Layers in Photovoltaic Properties of CH3NH3PbBr3 Heterojunction Solar Cells

초록

In a new heterojunction solar cell employing CH3NH3PbBr3 (MAPbBr3) as light absorber, we found that the introduction of a carboxylate monolayer on the mesoporous TiO2 surfaces significantly enhances JSC as well as VOC. In particular, the presence of a bromoacetate monolayer at the interface of TiO2/MAPbBr3 remarkably increases the photovoltaic conversion efficiency (PCE) from 2.65 % to 5.57 % with JSC of 5.411 mA/cm2, VOC of 1.372 V, and FF of 0.75. Time-resolved photoluminescence measurements indicate that presence of the interfacial carboxylate groups expedites electron injection from MAPbBr3 to TiO2. Furthermore, according to pulsed light-induced transient measurements (PLITM) of photocurrent analysis, the lifetime of photoinjected electrons (τe) in TiO2 conduction band (CB) significantly increases with the passivation of the interface, implying the suppression of charge recombination as well.