Study On Carrier Transport Of Perovskite Solar Cells

Organic-inorganic lead halide perovskite solar cells（PeSCs）can be prepared by simple solution engineering with an efficiency of 23.7%,which is a hot spot in the research and discussion of photovoltaic technology.Perovskite solar cell device optimization and physical mechanism research is currently the main research direction.Optimizing carrier transport performance is the main way to achieve high performance perovskite solar cell devices.This article optimizes the carrier transport properties of the electron transport layer（TiO2）,the perovskite light absorbing layer,and the hole transport layer spiro-OMeTAD.Prevent charge recombination and enhance conductivity.Finally,a battery device with high efficiency and low hysteresis was prepared.The main work and content include the following three aspects:（1）The optimization of the hole blocking layer in PeSCs is the most importance because it strongly affects device performance.The dense TiO₂（c-TiO₂）layer is an effective means to achieve fast carrier transport between FTO and perovskite and minimize electron-hole recombination.The simple method of doping the original precursor solution by TiCl₄ solution realizes the common coverage of the FTO-based,accelerates the transfer and transmission of electrons,effectively reduces the charge recombination,and achieves device efficiency of up to20%.Device efficiency has increased by nearly 43%.（2）The high-quality perovskite film with large grain size and little grain boundary is the main method to reduce the defect state and increase the carrier lifetime.Due to the uncontrolled solvent extraction process,the formed mesophase usually has unevenness,which ultimately affects the growth of perovskite grains.After solvent-evaporation post-treatment,a uniform perovskite intermediate phase is obtained after anti-solvent extraction,and then annealing can be performed to grow a large-grain perovskite film extending longitudinally through the entire absorption layer.It increases the carrier concentration,accelerates the longitudinal transfer and separation of charge,achieves a power conversion efficiency of 18.3%,and significantly prolongs the time window of the anti-solvent extraction process,effectively promoting the operability of practical applications.（3）Spiro-OMeTAD is currently the most important hole transport material,but the spiro-OMeTAD film which has been used for solution spin coating is highly disordered,which greatly reduces the mobility of hole carriers.For the structural characteristics of spiro-OMeTAD,a non-inhibited crystalline green solvent ethyl acetate was selected and an antisolvent methanol was assisted to grow a millimeter-sized spiro-OMeTAD single crystal.In comparison with amorphous powders or films,the carrier mobility and conductivity are increased by orders of magnitude.A crystalline spiro-OMeTAD is applied to a perovskite solar cell device.The carrier is more favorable due to its higher conductivity.A device performance with a hysteresis reduction efficiency of 18%was obtained.In summary,we optimize the carrier transport performance of each functional layer by different methods to achieve efficient battery device fabrication.It provides important practical experience and theoretical basis for further efficient and stable perovskite solar cells.