Researchers from China's Southeast University and Beijing Information Science and Technology University have explained that charge transport layers play a big role in facilitating the extraction and injection of carriers in perovskite solar cells (PSCs), but the performance of PSCs fabricated with conventional charge transport materials tends to exhibit significant hysteresis and instability.
To address this issue, the team used the composite TiO₂/SnO₂ with superior electron mobility and stability and the low-cost CuSCN as bilayer electron transport layer (ETL) and hole transport layer (HTL) materials, respectively. The PSCs with the p-n-n (p-type FAxMA1-xPbIxBryCl3-x-y (FA=CH(NH2)2), MA=CH3NH3)-n-type SnO2-n-type TiO2) construction of FTO/TiO2/SnO2/FAxMA1-xPbIxBryCl3-x-y/CuSCN/C/FTO have been investigated via computation simulation and experiment. It was observed that the performance of PSCs with p-n-n structure surpassed that of n-n-p (n-type SnO2-n-type TiO2-p-type FAxMA1-xPbIxBryCl3-x-y) structure, benefiting from the existence of the bilayer ETL with p-n-n structure, which improves the collection ability, and the lifetime and mobility of photogenerated carriers.
The perovskite thin film can be uniformly covered by the CuSCN HTL with 25 μL CuSCN drop-coating solution, which effectively reduced the hysteresis of the device under atmospheric conditions during the experiment.
Furthermore, the team also demonstrated that the thickness of the functional layers, conduction band offset, doping concentration, and operating temperature play crucial roles in determining the photophysical and photoelectric properties of PSCs.
The simulation results imply that the PSCs not only have high power conversion efficiency (PCE) (17.7619%) at 295 K but also maintain impressive stability.
This work could provide an effective strategy for the realization of high efficiency and long-term stable carbon-based PSCs.
