Passivating SnO2/perovskite interface via guanide hydrochloride toward efficient and stable n-i-p perovskite solar cells

Nonradiation recombination of interfacial carriers is a key factor hindering the improvement of efficiency and stability of perovskite solar cells (PSCs). Here, we report an effective electron transport layer/perovskite interface regulation strategy. By introducing the multifunctional molecule guanidine hydrochloride (GCl) on the surface of SnO2, we can enhance the electron extraction between SnO2 and perovskite and promote the growth of high-quality perovskite films. GCl is anchored on the surface of SnO2 and interacts with undercoordinated ions in perovskite. The experimental results show that GCl has interaction with both SnO2 and perovskite layer, and a "bridge" connection is formed between the two layers. This strategy not only passivates the SnO2/perovskite interface defects, improves the perovskite crystallization quality, but also helps to reduce the interface charge accumulation. More importantly, the PCE of GCl passivated device reached 21.63 %, which was much better than that of control device (19.56 %). In the air environment, after 30 days at room temperature, the GCl modified unpackaged device maintained 83 % of its initial efficiency. Therefore, interface modification with GCl is an effective strategy to improve the interface state, improve the crystallization quality and obtain high-performance PSCs.