Black phosphorus quantum dots as an effective perovskite interfacial modification layer for efficient low-temperature processed all-inorganic CsPbI2Br perovskite solar cells

Developing high-performance perovskite solar cells (PSCs) with all of the functional layers fabricated at low temperature (< 180 degrees C) is highly desirable for the roll-to-roll processing of CsPbI2Br based PSCs. As for the all inorganic perovskite, it is still a challenge to obtain void-free perovskite film especially prepared at this condition. Herein, we develop a facile approach to optimizing the morphology of low-temperature processed all inorganic perovskite via using black phosphorus quantum dots (BPQDs) as an excellent interfacial modification material atop the perovskite layer for the first time. It is found that high-electron-mobility BPQDs can fill the voids between the grains of the perovskite film to provide more efficient pathways for electron extraction. Moreover, the BPQDs modification can effectively reduce the surface trap density of the perovskite layer, in addition to enhance the absorption of the PSC, thus suppressing nonradiative recombination losses. As a result, by incorporating BPQDs as the interfacial modification layer, our designed all-inorganic PSCs produce a maximum PCE of up to 12.2%. Furthermore, such highly efficient CsPbI2Br based PSC combined with the full low temperature processing is rare, even outperforming most of previously reported CsPbI2Br based PSCs.