Cerium and zinc co-doped nickel oxide hole transport layers for gamma-butyrolactone based ambient air fabrication of CH3NH3PbI3 perovskite solar cells

Highlights: • First-time demonstration of Ce and Zn co-doped NiO_xlayers and employment in inverted perovskite solar cells. • Co-doping with an optimum ratio of Ce and Zn increased the work function, electrical conductivity, hole concentration, and mobility of the NiO_xlayers. • Enhanced interface quality and decreased trap density in perovskite layer resulted in better device stability. • Fully solution-processed perovskite solar cells fabricated under 50–55% humidity using only γ-butyrolactone employed perovskite precursor for methylammonium lead tri-iodide and record power conversion efficiencies achieved. Cerium and zinc co-doped nickel oxide (NiO_x) hole transporter layers (HTLs) developed for boosting the efficiency and stability of inverted methylammonium lead tri-iodide (CH₃NH₃PbI₃) based glove box-free fabricated solar cells. Combining our humidity resistive gamma butyrolactone-based perovskite deposition route with an optimum doping ratio of NiO_x:Zn-Ce (18:6 mmol %) layers, power conversion efficiencies boosted from 10.04% to 14.47% and stability is increased under aging conditions. This performance enhancement was questioned over NiO_x layers, quality of perovskite layer and the interface between charge transport layers and perovskite. Zn doping increased the electrical conductivity while incorporation of Ce created a positive impact on surface morphology and interface quality by a decreased roughness compared to the only Zn doped layers. The work function, hole mobility and concentration were found to increase with co-doping. Besides, the trap density of the perovskite layer is lessened, hindering unfavorable charge recombination confirmed by space charge limited current (SCLC) and photoluminescence (PL) analysis.