Depth-dependent defect manipulation in perovskites for high-performance solar cells

Defects at the bulk grain boundaries and heterojunction interfaces could dictate the power losses of perovskite solar cells (PSCs) during the operation process, which are regarded as major roadblocks towards further development of this emerging photovoltaic technology. The common modulation strategies reported for the state-of-the-art cells cannot concurrently heal the defects located at the grain boundaries and interfaces. Herein, a depth-dependent manipulation strategy is demonstrated to concurrently modulate the bulk and interfacial defects in the perovskite films. According to the distinct penetrability of the employed binary modulators within the polycrystalline perovskite film, one of the modulators can penetrate through the bulk to the buried interface, accompanied by bulk and buried interface defect healing, while the other remains to anchor atop the surface along with the surface defect modulation, assuring simultaneous defect management from the interfaces to the bulk. As a result, the mitigated non-radiative losses and the improved charge transport of the modulated perovskite film boost the efficiency of PSCs from 21.79% to 24.36%. This universally effective depth-dependent manipulation strategy provides new insights into spatial defect modulation, which would open up a promising way for defect modulator design for highly efficient perovskite optoelectronic devices.