Improved Efficiency of Perovskite Solar Cells Using a Nitrogen-Doped Graphene-Oxide-Treated Tin Oxide Layer.

Tin oxide (SnO) is widely adopted as an electron transport layer in perovskite solar cells (PeSCs) because it has high electron mobility, excellent charge selective behavior owing to a large band gap of 3.76 eV, and low-temperature processibility. To achieve highly efficient SnO-based PeSCs, it is necessary to control the oxygen vacancies in the SnO layer, since the electrical and optical properties vary depending on the oxidation state of Sn. This study demonstrates that the performance of PeSCs may be improved by using nitrogen-doped graphene oxide (NGO) as an oxidizing agent for SnO. Since NGO changes the oxidation state of the Sn in SnO from Sn to Sn, the oxygen vacancies in SnO can be reduced using NGO. Multiple devices are fabricated, and various techniques are used to assess their performance, including X-ray photoelectron spectroscopy, dark current analysis, and the dependence of the open-circuit voltage on light intensity. Compared with the average power conversion efficiency (PCE) of control devices, PeSCs with SnO:NGO composite layers exhibit greater PCEs with less deviation. Therefore, the introduction of NGO in a SnO layer can be regarded as an effective method of controlling the oxidation state of SnO to improve the performance of PeSCs.