Defect engineering of oxygen vacancies in SnOx electron transporting layer for perovskite solar cells

In this work, we present the self-passivation of tin oxide (SnO x ) electron transporting layer (ETL) induced by manipulatively filling the oxygen vacancies for perovskite solar cells (PSCs). The oxygen component of SnO x ETL is tuned by the annealing under the oxygen (O 2 ) atmosphere to control the trap state density for high electron collection efficiency. With increasing the O 2 content when annealing, oxygen vacancies of SnO x ETL are filled gradually, with the x of SnO x being up to 1.84, while the crystalline structure grown better to be rutile. Furthermore, the measurement of electron transport dynamic demonstrates that the SnO x ETL is benefit for electron collection after O 2 -annealed, and receiving high power conversion efficiency (PCE) of PSCs. The PSC based on the O 2 -annealed SnO x ETL yields an average PCE of over 19%, much higher than 17.81% of that after N 2 -annealing. The O 2 -annealed PSC gives a champion PCE of 20.40%, with a short current density of 24.41 mAcm −2 , an open circuit voltage of 1.14 V and a fill factor of 73.37%. Therefore, the annealing is an efficient and simple way to control the quality of SnO x ETL for the high performance PSCs.