Simultaneously enhancing dissociation and suppressing recombination in perovskite solar cells

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.