This article reports the experimental studies on simultaneously enhancing the dissociation and suppressing the recombination in perovskite solar cells by using high-dielectric Nickel Oxide (NiOx) as hole transport layer. Specifically, the magneto-photocurrent, generated by the electron-hole pairs, surprisingly becomes negligible at short-circuit condition when the NiOx is used to replace the poly (3,4-ethylenedioxythiophene) poly (styrene-sulfonate) (PEDOT:PSS). This indicates that the NiOx transport layer leads to a complete dissociation of electron-hole pairs in perovskite layer. On the other hand, the negligible magneto-photocurrent can be recovered to become appreciable when a forward bias is applied towards open-circuit condition to weaken the built-in field. This magneto-photocurrent result suggests that the NiOx transport layer enhances the built-in field, completely dissociating the electron-hole pairs. Furthermore, the photoinduced capacitance studies confirm that the built-in field is enhanced essentially through static and dynamic parameters, by removing the interfacial traps and decreasing the accumulation of photogenerated carriers. The time-resolved photoluminescence shows that the NiOx/CH3NH3PbI3 interface leads to a reduction on non-radiative recombination, increasing the fraction of useful excitons available for photovoltaic actions. Moreover, the field-dependent photoluminescence measured alternatively at short-circuit and open-circuit conditions shows that the NiOx layer can also suppress the radiative recombination within available excitons, boosting the photovoltaic actions. Therefore, our studies reveal that the high-dielectric NiOx transport layer can simultaneously enhance the dissociation of electron-hole pairs and suppress both non-radiative/radiative recombination, leading to the more efficient generation of Jsc and Voc in perovskite solar cells.
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