Adaption of MAPbI3 perovskite with copper phthalocyanine inorganic hole transport layer via nitrosonium tetrafluoroborate additive to enhance performance and stability of perovskite solar cells

Due to their high resistance to real operational conditions, perovskite-based solar cells (PSCs) with dopant-free inorganic hole transport materials are good candidates for PSC commercialization. It should be noted that these types of PSCs have recorded lower power conversion efficiency (PCE) compared to Spiro-OMeTAD-based PSCs, with a recent PCE record of 25.8%. Here, we introduced nitrosonium tetrafluoroborate (NOBF4) into the perovskite precursor to improve hole carriers' transport between the perovskite layer and copper phthalocyanine (CuPc) layer. Electrochemical impedance spectroscopy (EIS) showed that NOBF4 additive reduces series resistance in PSC devices, which may be due to a band alignment between the valance band of perovskite and CuPc. In addition, due to a partial BF4- substitution with I- ions during the fabrication process, the crystallinity properties of the perovskite layer are tailored, leading to the formation of a film with larger grains. By employing NOBF(4 )material, in the obtained perovskite layer, a small unreacted lead iodide (PbI2) amount remained. In total, the NOBF4 additive brings a maximum efficiency of 16.77% for the target solar cell group, higher than the 14.42% for control devices. The target PSCs, compared with the control PSCs, showed improved air stability results from the suppressed PbI2 with enlarged perovskite grains.

Automated summary

Dopant-free inorganic hole transport materials show high resistance and potential for commercialization of perovskite-based solar cells. Introducing NOBF4 as an additive improves efficiency and air stability of the solar cells.