Chinese researchers have built one of the most efficient carbon electrode perovskite solar cells reported to date. The device uses an organic/inorganic planar hole transport layer structure that is claimed to have superior electrical contact.
Researchers at Henan University in China have produced a perovskite solar cell based on a carbon electrode that is said to achieve a power conversion efficiency of 20.8 percent while improving stability.
Metal contact electrodes commonly used today can stimulate the degradation of perovskite solar cells due to the diffusion of metal impurities across the interfaces. This problem could theoretically be solved by replacing the metal contact with carbon electrodes, which are very promising for commercialization because their processability at ambient pressure is based on industrially established printing techniques.
However, perovskite solar cells based on carbon electrodes present a problem elsewhere in the devices, leading to performance degradation where the carbon electrode meets the perovskite layer.
“In carbon electrode perovskite solar cells, the interface between the carbon electrode and the perovskite plays a major role in the performance of the solar cells,” the researchers said. “Most inorganic hole transport layers (HTLs) are based on dispersive nanoparticles that can easily aggregate to form a rough contact with both the perovskite and the viscous carbon paste; this negatively affects hole collection.”
They sought to solve this problem by sandwiching an organic semiconducting polymer called polythiophene (P3HT) between the perovskite and the HTL made of nickel(II) oxide (NiOx), and said that this organic/inorganic planar HTL structure has superior electrical contact to the carbon electrode perovskite solar cell. cells.
“The organic P3HT layer enables efficient moisture settlement and a tightly contacted interface where the energy level is aligned with the perovskite, while the stable NiOx nanoparticle layer further protects the P3HT from carbon paste corrosion so that we can further optimize the spread of the carbon blade coating forming a tight contact with the HTL” , they also explained.
The Chinese group built the cell with a substrate made of indium tin oxide (ITO), a tin(IV) oxide (SnO2) buffer layer, a perovskite absorber, a P3HT layer, an HTL made of NiOx, and a carbon electrode.
The electrode is based on a carbon paste containing carbon black and graphite powder supplied by Saidi Technology Development Inc., China. “The carbon electrode was prepared by a tip coating process and the wet film was annealed at 110 C for 5 minutes,” it said.
The researchers compared the performance of the solar cell to a reference device without the modified anode-buffer interfaces, which they say can facilitate charge collection.
The master solar cell constructed with these interfaces achieved a power conversion efficiency of 20.8%, a breakdown current of 1.15 eV, a short-circuit current of 22.9 mA/cm2, and a fill factor of 78.8%.
“This efficiency is one of the highest for carbon-electrode perovskite solar cells; a peak efficiency of 22% was reported for a half-cell assembly on a carbon-electrode substrate,” they noted. “The functional stability of this cell is clearly enhanced by the hydrophobic P3HT layer and dense carbon precoating.”
The efficiency of the comparison device, on the other hand, only reached 13.4%.