Aromatic carboxyl acid regulated nanoparticle deposition and passivation of tin oxide for high performance perovskite solar cells

The composition and nano particle agglomeration of hydrolyzed species in chemical bath deposition (CBD) plays a key role in obtaining efficient SnO2 film for high performance perovskite solar cells (PSCs). In this work, the aromatic acids with varied carboxyl groups were investigated to regulate the nano particle deposition and passivate the buried SnO2/perovskite interface. The quasi in-situ dynamic light scattering and Zeta potential results indicated that the nano particle agglomeration with trimesic acid (TMA) was significantly refined throughout the whole deposition process. The TMA-SnO2 achieved an ideal energy band alignment with perovskite and released the internal residual strain, promoting the growth and crystallization of the perovskite film due to the corrdination of carboxyl groups. As a result, the interface defects were effectively passivated with enhanced efficiency and stability. The small area device based on TMA-SnO2 obtained an efficiency of 25.07 %. The devices with an enlarged area of 1.4 cm2 and the 5x5 cm2 mini-module (active area 10.054 cm2) showed impressive PCEs of 23.93 % and 22.40 %, respectively. Furthermore, the unencapsulated devices exhibited enhanced long-term stability, maintaining 80 % and 90 % of the initial efficiencies under 80 +/- 5 degrees C thermal annealing in nitrogen for 1176 h and in air condition for 3224 h, respectively.