Improving Performance Of Perovskite Solar Cells Via Modifying Electron Transport Layer

Perovskite solar cells (PSCs) have been attracting considerable research attention owing to their advantage of ever-increasing power convernsion efficiency (PCE), low cost, simple process and high-flexibility. Several practical methods to efficiency improvement of PSCs have been developed, including enhancing the crystallinity of perovskite material, synthesis of new perovskite materials, micro-morphology control of the perovskite photoactive film and modification of electron transport layer (ETL) or hole transport layer (HTL). In this thesis, we focused on enhancing PCE of inverted structure perovskite solar cells (ISPSCs) devices by modifying PCBM ETL, and carried out the following two works:(1) An amphiphilic surfactant, oleamide, was for the first time applied to dope PCBM ETL, resulting in dramatic efficiency enhancement of ISPSC devices. Under the optimized oleamide doping ratio of5.0wt%, PCE of the CH3NH3PbIxCl3-x perovskite-based ISPSC device is enhanced from10.05%to12.69%, and such a PCE enhancment of26%is primarily due to the increases of both fill factor (FF, from61.8%to69.3%) and short-circuit current (Jsc, from17.08mA/cm2to18.76mA/cm2). According to the surface morphology study of the perovskite/PCBM bilayer film, oleamide doping improves the coverage of PCBM ETL onto the perovskite layer, and this is beneficial for the interfacial contact between the perovskite layer and the Ag cathode and consequently the electron transport from perovskite to the Ag cathode. Such an improved electron transport induced by oleamide doping is further evidenced by the impedance spectroscopic study, revealing the prohibited electron-hole recombination at the interface between the perovskite layer and the Ag cathode..(2) A Water-soluble non-conjugated polymer Poly(vinylpyrrolidone)(PVP) was spin-coated onto PCBM ETL, leading to efficiency enhancement of ISPSC devices. Under the optimized PVP incorporating condition (isopropanol was used as solvent, solution concentration:1.0mg/mL, spin-coating speed:3000rpm), PCE of the CH3NH3PbIxCl3-x perovskite-based ISPSC device is enhanced from9.07%to11.98%, and such a PCE enhancment of32%is is primarily due to the increases of both fill factor (FF,16%enhancement) and short-circuit current (Jsc,10%enhancement). According to the UV-vis absorption spectroscopic study, PVP incorporation did not affect the absorbance of perovskite photoactive layer, therefore efficiency enhancement is not attributed to the change of the absorbance of perovskite photoactive layer. Further study is need to understand the underlying efficiency enhancement mechanism.