Low-temperature solution-processed Mg: NiOx hole transport layers for formal (n-i-p) perovskite solar cells

NiO x is one of the most promising inorganic hole transport materials for perovskite solar cells . However, lots of fabrication methods refer to NiO x are limited in n-i-p type perovskite solar cells. Because the deposition procedure of NiO x film such as polar solvents and high temperature process is seriously incompatible with perovskite light-absorption underlayers. In this work, highly crystalline NiO x nanocrystals are prepared using solvothermal method under the presence of long-chain oleylamine molecules. The resulted NiO x nanocrystals can be easily dispersed in weak-polar toluene and form films on perovskite layer without annealing procedure. The n-i-p type device with NiO x hole transport layer achieves an efficiency of 10.34%. Later, Mg 2+ with different molar ratios are incorporated into the NiO x nanocrystals. It is found that introducing a certain amount of Mg 2+ benefits to improve the ratio of Ni 3+ /Ni 2+ , thereby changing the work function and increasing the hole conductivity. As a result, the n-i-p type device with Mg-NiO x hole transport layer yields an improved efficiency of 12.41%.