Recent advances and future directions to optimize the performances of p-type dye-sensitized solar cells

[Display omitted] ► We have examined the key factors affecting the efficiency of NiO based DSCs. ► The main causes of low efficiency are interfacial current losses and fast charge recombination reaction leading to poor fill factor, low short current density and low open circuit potential. ► Molecular dyads can slow down charge recombination and increase the photocurrent. ► Cobalt based electrolyte can reduce charge interception of the holes in NiO by the redox mediator and increase the fill factor and open circuit potential. ► A new p-type semiconductor is certainly the key target for future improvements to these devices. This review provides a summary of the most important developments in the field of solar cells based on the sensitization of p-type semiconductors, such as NiO, and identifies the future challenges and opportunities to enhance their overall performance. In particular, the main factors responsible for the low open-circuit voltage, short circuit photocurrent and fill factor are discussed in detail.