Fabrication Of High-efficiency Perovskite Solar Cells Based On Simplified Structure

To face important issues such as“energy crisis”and environmental pollution,the exploitation and utilisation of renewable energy resources is nowadays a priority for humankind.As an inexhaustible and clean resource,solar energy has always been a research focus of scientists.Photovoltaics as a technology that makes efficient utilisation of solar energy is the most promising alternative to address these issues.Over the last few decades,many photovoltaic technologies have emerged.Among these photovoltaics,perovskite solar cells（PSCs）is definitely the most promising due to their dramatic growth of power conversion efficiency（from 3.8%to 24.2%within only 10years）,low cost and solution processability.Although major problems,including the toxicity of perovskites and the long-term device stability,still remain to be solved for PSCs,the feasibility of their commercialisation has been investigated.The commercialisation of PSCs requires high efficiency,low material cost and simple manufacturing procedure.To meet these requirements,it is crucial to simplify the device structures while maintaining high efficiency.Therefore,in this dissertation,we focused on the simplification of the device structures in PSCs and the main works are as follows:（1）The preparation of high efficiency hole transport layer（HTL）-free perovskite solar cells can greatly promote the commercialization of PSCs.However,removing of HTL directly typically results in a significant decrease in device efficiency due to the energy levels mismatch at the ITO/perovskite interface.In order to solve this issue,we introduced a 4,4’-Cyclohexylidenebis[N,N-bis（4-methylphenyl）benzenamine]（TAPC）monomolecular layer（TAPC-ML）on bare ITO.The interface dipole created by Sn-N bond between the TAPC monolayer and the ITO effectively raised the work function of the ITO and reduced the energy level barrier（ΔE_h）at the ITO/perovskite interface.The reducedΔE_h at the ITO/perovskite interface effectively improved the charge transfer efficiency at the interface and suppressed the non-radiative carrier recombination.Hole transport layer-free perovskite solar cells with the structure of ML-ITO/perovskite/C₆₀/BCP/Ag was fabricated.The HTL-free PSCs based on the ML-ITO yields an efficiency of 19.42%,much higher than those of HTL-free PSCs on bare ITO（10.26%）.（2）In order to further simplify the device structure,we eliminated the additional fabrication process of the conventional electron transport layer by forming a perovskite-electron transport layer heterojunction using a unique solvent engineering（PCBM（[6,6]-phenyl-C61-butyric acid methyl ester）solution dripping）method.Finally,ultra-simplied device structure:ML-ITO/perovskite-PCBM/BCP/Ag was fabricated.During the formation of the perovskite-electron transport layer heterojunction,part of the PCBM can be reserved in the perovskite films,which facilitated carrier extraction and transfer and reduced carrier recombination.While others will form a thin and uniform PCBM layer atop the perovskite crystal,serving as a conventional electron transport layer.When the PCBM solution concentration was optimized to 15 mg/mL,the ultra-simplied structure device exhibited a higher maximum PCE of 19.61%compared with that from the conventional method（15.12%）.The ultra-simplied structure device also showed excellent long-term stability,maintaining nearly 90%of the original efficiency after 60 days without encapsulation under ambient atmosphere.