Egyptian researchers have developed a new hole transport layer (HTL) for inverted perovskite solar cells using silver thiocyanate instead of the commonly used PEDOT:PSS and copper thiocyanate. The new HTL material showed exceptional efficiency and stability in the constructed cell.
“The advantages of CuSCN lie in the fact that it can act as both a hole transport layer and a source of Cu doping, while AgSCN with better resistivity can only act as a source of Ag doping with a slower diffusion rate,” the researchers. explained, noting that AsSCN is also better at transferring charges between the HTL and perovskite layer compared to PEDOT:PSS.
The team built the cell on an indium tin oxide (ITO) substrate, an Electron transport layer (ETL) based on AgSCN, an absorber based on a type of lead halide perovskite known as methylammonium lead iodide (MAPbI3), phenyl C61 butyric acid methyl ester layer (PCBM)., bathocuproin (BCP) buffer layer, and a silver (Ag) metal contact.
The academics placed the AgSCN thin film in a dry glove box with a relative humidity of 25–30% for at least 30 minutes before starting the deposition of the perovskite layer. They then deposited a perovskite layer on the HTL active layer by spin coating at 4,000 rpm for 30 seconds. The performance of the solar cell was compared to a reference device built with an HTM based on PEDOT:PSS.
The AgSCN-based device achieved a power conversion efficiency of 16.66%, a breakdown voltage of 1.14 mV, a short-circuit current of 19.0 mA/cm2, and a duty cycle of 77.1%. The PEDOT:PSS cell achieved 15.11% efficiency, 1.04 V open circuit voltage, 18.17 mA/cm2 short-circuit current, and 80.37% fill factor.
“The successfully achieved AgSCN thin film made a better perovskite film with free holes and large grains, while the PEDOT:PSS thin film made a perovskite film of similar quality with observed holes,” the team explained, noting that the AgSCN cell was also able to retain 80.9% of its original efficiency after 500 hours in an atmosphere with a relative humidity of 48%.
“This low-temperature and low-cost AgSCN production method is seen as facile and scalable, which bodes well for the commercialization of perovskite-based flexible devices and photovoltaic technologies,” the researchers concluded. “In summary, AgSCN is a non-toxic, low-cost competitor that is easy to work with at low temperatures. It is a strong contender for the creation of perovskite tandem devices and high efficiency pin junction solar cells.
They described the cell technique in “AgSCN as a novel hole-transporting material for inverted perovskite solar cells,” published recently Scientific reports.