Computation simulation and experiment investigations of stable co-doping perovskite solar cells with TiO2/SnO2 bilayer and CuSCN structures

Abstract

The charge transport layers play a momentous role in facilitating the extraction and injection of carriers in perovskite solar cells (PSCs). Unfortunately, the performance of PSCs fabricated with conventional charge transport materials exhibits significant hysteresis and instability. Here we utilise 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 FA_xMA_1-xPbI_xBr_yCl_3-x-y (FA=CH(NH₂)₂), MA=CH₃NH₃)-n-type SnO₂-n-type TiO₂) construction of FTO/TiO₂/SnO₂/FA_xMA_1-xPbI_xBr_yCl_3-x-y/CuSCN/C/FTO have been investigated via the computation simulation and experiment. It has been observed that the PSCs performance of p-n-n structure surpasses that of n-n-p (n-type SnO₂-n-type TiO₂-p-type FA_xMA_1-xPbI_xBr_yCl_3-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 reducing the hysteresis of the device under the atmosphere conditions during the experiment. Furthermore, we further demonstrate that the thickness of 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 we designed and optimized not only have high power conversion efficiency (PCE) (17.7619%) at 295 K but also maintain ascendant stability. This work shall provide up an effective strategy for the realization of high efficiency and long-term stable carbon-based PSCs.