Morphology Control For Perovskite Solar Cells Absorber And Its Effects On Photovoltaic Performance Of Device

Organic-inorganic halide perovskite materials have a lot of fascinating properties,such as high absorption coefficient,high carrier mobility and tunable band position and bandgap.The power conversion efficiency(PCE)of perovskite solar cells(PSCs)has risen to 22%in the past few years.In addition,PSCs can be fabricated by solution-processed technique,which is simple and cost-effective.Consequently,organic-inorganic halide perovskites offers promising prospects for high efficiency and low cost solar cell.To achieve the commercialization of PSCs,there are many aspects for the improvement of the PCE of devices.The effect of the morphology of perovskite film on the performance of PSCs is particularly critical.Besides,controlling the morphology of perovskite absorber is also one of the research hot spots in PSCs.Therefore,my research focused on this main issue.1.A new deposition process,continuous dripping method,was proposed for fabricating PSCs.First,dimethyl sulfoxide(DMSO)was introduced into the precursor solution of lead iodide at a specific molar ratio,and the conditions of the formation of perovskite film via conventional solution two-step method process were explored.It was found that the surface morphology of CH3NH3PbI3(MAPbI3)films prepared via this process was porous and rough,resulting in poor performance device with PCE lower than 7%.In order to solve this problem and improve the efficiency of the devices,a continuous dripping method was proposed.High quality MAPbO=I3 films with good crystallinity and satisfactory morphology was achieved via this process.Meanwhile we analyzed the effects of intermediate phase PbI2(DMSO)2 on the crystallinity and morphology of perovskite thin films,and studied the effects of PbI2 sample and CH3NH3I(MAI)solution concentration on the perovskite film morphology and device efficiency.The PCE of PSCs has risen to 14%via this process.We also found that there was a crack between the crystal grains of perovskite thin film prepared via the continuous dropping method,which hindered the improvement of the device performance.2.To solve the problem of film cracking,the continuous dripping process was further optimized.The morphological control and performance improvement of MAPbI3-based PSCs were further studied.We have systematically investigated the impact of different molar ratio of PbI2 to DMSO on the growth,morphology and crystallinity of MAPbI3 films obtained via this process.The high PCE PSCs obtained from crack-free and highly crystallographic perovskite films prepared with optimized ratio of PbI2 to DMSO in first precursor solution.The best PCE of 17.76%and an average PCE of 16.37±0.51%were obtained via this process.Moreover,the conventional two-step spin coating process was also carried out as a comparison to our process.The impacts of fabrication techniques on morphologies of perovskite materials and the resultant PCE of PSCs was analyzed.The superiority of continuous dropping process has been further reflected through comparison results.In conclusion,this work provides an effective and simple solution process to obtain high quality perovskite thin films for high-performance and reproducible PSCs.