Carbon quantum dot-incorporated nickel oxide for planar p-i-n type perovskite solar cells with enhanced efficiency and stability

Carbon quantum dots (CQDs) have attracted extreme interest as a promising nanocarbon platform for divergence optoelectronics due to their high stability, good dispersibility in solvents, and tunable optical and electronic properties. Herein, planar p-i-n type perovskite solar cells (PSCs) with enhanced efficiency and long-term stability were developed by incorporating CQDs into a nickel oxide (NiO) hole transport layer (HTL). The incorporation of CQDs downshifts the band structure of NiO, leading to good alignment with the work-function of the tin-doped indium oxide (ITO) electrode and the band-edges of the perovskite. The efficient cascade charge transport achieved with the optimized incorporation ratio of CQDs resulted in an enhanced power conversion efficiency (PCE) of 17.02%, compared to that of the PSC fabricated with bare NiO (15.66%), even though they were fabricated in air. The suppressed charge recombination accompanied by restricted charge accumulation curtails the J-V hysteresis, with a reduction from 4.5% to less than 1%. Moreover, long-term stability under atmospheric conditions without any encapsulation was achieved with CQD-incorporated NiO. More than 70% of the initial PCE was retained over 190 h. This work suggests a novel strategy for fabricating solution-processible metal oxide interlayers with highly efficient charge migration for divergence energy conversion devices. •Carbon quantum dots (CQDs) incorporated in NiO hole transport layer (HTL).•Perovskite solar cells with enhanced efficiency and long-term stability by CQDs incorporated NiO HTL.•Good match with the work-function of the ITO electrode.