A full range of defect passivation strategy targeting efficient and stable planar perovskite solar cells

Defects and inferior charge transport dynamics within devices are key issues that inhibit the improvements of photovoltaic performance and stability. Developing facile and feasible strategies for synchronous passivation of defects regarding charge transport layers (CTLs), perovskite films and their interfaces, and precise tuning of energy level structure, is a definite way to solve above problems. Herein, we develop a synergistic passivation strategy for perovskite films and bilateral interfaces to improve device performance. Firstly, an appropriate amount of phenylethylammonium chloride is adopted to modify SnO2 electron transport layer (ETL). The complexation reaction between N atoms in -NH2 and Sn4+ improve the agglomeration of SnO2 nanoparticles and film quality of SnO2 ETL. The presence of Cl- ions not only effectively fill oxygen vacancies within SnO2 ETL, but also participate in regulating crystal growth dynamics of perovskite films, thus improving electron transport properties at interface. Subsequently, p-type conducting material N,N'-Bis-(1-naphthalenyl)-N,N'-bis-phenyl(1,1 '-biphenyl)-4,4 '-diamine (NPB) is introduced into anti-solvent chlorobenzene during the preparation of perovskite films to further regulate the crystal quality and achieve full-range defect passivation. Particularly, the introduction of NPB helps to construct a gradient heterojunction between upper perovskite film and SpiroOMeTAD hole transport layer, thus reducing the accumulation of hole carriers near interface and further suppressing current-voltage hysteresis behavior of devices. Additionally, the hydrophobicity of NPB and full range of defect passivation greatly enhance the humidity and thermal stability of devices. Finally, a high power conversion efficiency of 21.88% is obtained with suppressed hysteresis and enhanced long-term stability. This work highlights the role of full-range defect passivation on CTLs, perovskite absorption layers and interfacial charge transport properties, which provide a novel concept for constructing high-performance and stable perovskite devices.