Effects of Doped Hole-Transporting Layers on Perovskite Solar Cell Performances

The influences of doped hole-transporting layers (HTLs) on the performances of perovskite solar cells were studied. The influences of electrostatic and surface roughness effects using solvent additive doping were compared. The electrostatic effect of solvent additive doping was compared through the addition of 1,8-diiodooctane and 1,8-dichlorooctane to the HTL. The surface roughness effect of solvent additive doping was examined using atomic force microscopy. The perovskite crystallinity of doped HTLs was studied using X-ray diffraction. The conductivity of HTLs was measured using four probe methods and was higher for doped devices. The enhanced conductivity of PEDOT: PSS film was also proved using fluorescence emission quenching. The long-term stability of the device was enhanced through doping HTLs. The device with the solvent additive exhibited much greater enhanced stability retained over 80% of the initial PCE for 400 h, while PCE of the device without the solvent additive decreased to less than 80% after 200 h. A very weak power microwave treatment was used for the post-annealing of the fully fabricated devices. Post-annealing enhanced the lifetime of the device. Comparing different sizes of cells, the device lifetime was decreased as the cell area increased and as the size of the cell increased; the extent of lifetime enhancement through doping was increased.