Decreased surface defects and non-radiative recombination via the passivation of the halide perovskite film by 2-thiophenecarboxylic acid in triple-cation perovskite solar cells

Organic-inorganic lead halide perovskite solar cells (PSCs) attract great research interest due to their significant device performance and optoelectronic properties. However, reducing charge recombination and efficiency loss due to surface defects of the perovskite layer are still big issues to overcome for PSCs. Herein, we have employed a simple molecule, 2-thiophenecarboxylic acid (2TiCOOH), via post-treatment to passivate the uncoordinated Pb2+ on the perovskite film surface and improve the stability at the perovskite/Spiro-OMeTAD interface. The spectral results illustrate that the 2TiCOOH passivated devices exhibit higher carrier lifetime, charge extraction, and minimized defect induced recombination. Also, solar cells with 2TiCOOH show better charge collection, improved J(SC), FF, and outstanding power conversion efficiency (PCE). In addition, 2TiCOOH passivated solar cells show tremendously stable performance output with less than 1% PCE drop after 100 days. This work provides a facile surface passivation strategy for fabricating highly efficient, low cost, and stable perovskite solar cells, which can be used for large scale technology and commercialization.