| Energy sources play a decisive role in modern civilization and daily life.In the context of the global response to energy shortage and climate change,energy security has increasingly become the focus of common concern of all mankind.Solar energy is broadly recognized as clean,low-cost and reliable technology that has the advantages of abundant resources,unlimited supply over the years and widely distribution.Nowadays,photovoltaics has gradually become an important energy technology for social development.As a semiconductor device that directly converts photon energy into electrical energy,the development of solar cells has benefited from a variety of absorber materials and device configurations,such as inorganic semiconductor based monocrystalline silicon,polycrystalline silicon,amorphous silicon,cadmium sulfide film and gallium arsenide,etc.Although the power conversion efficiency（PCE）of the representative solar cells has been very close to their thermodynamical limit,namely Shockley-Queisser limit（～33%）,their large-scale applications are still limited by the high manufacturing cost at this stage.As a promising photovoltaic technology,organic solar cells（OSCs）have drawn extensive attention from researchers around the world.At present,the maximum power conversion efficiency of reported single junction OSCs has exceeded 19%,which would encourage and stimulate more research for the design of organic photovoltaic materials and devices.Organic photovoltaic materials possess many unique advantages,such as tunable chemical structure,tunable electronic energy levels and optical properties,while the fabrication of organic photovoltaic devices can be achieved through low-cost,high-throughput printing technology.Nevertheless,it should be pointed out that the power conversion efficiency of organic solar cells is relatively low,while their stability issue still remains a big challenge.It should be noted that at present,OSCs rely on indium tin oxide（ITO）as transparent conductive electrode,which is another limitation that need to be overcome imposed by shortage of tin element.In order to resolve the above problems,it is of great significance to further develop promising organic photovoltaic materials and develop effective methods to enhance their performance continuously.Starting from the research on the preparation and working mechanism of high-efficiency devices for organic solar cells,this thesis attempts to study and explore the physical mechanism behind the device structure optimization and photoelectric conversion process of organic solar cells from three aspects:i)the optimization of electrode layers,ii)the influence of different interface modification layers on device performance,and iii)the energy loss mechanism of non-fullerenes material systems.We also attempt to analyze the reasons for the impact of new structural substrates on device performance,and to gain a deeper understanding of the mechanism of performance enhancement based on non-fullerenes acceptor material systems,which have become very popular in recent years.The main results are summarized as follows:1.High-performance gallium-doped zinc oxide GZO/Ag/GZO multilayer structured transparent conductive electrodes were deposited on glass substrates by magnetron sputtering technique through optimizing oxygen flow,thickness of GZO and thermal annealing treatment.In a comparative study of optical and electric properties with the most commonly used indium tin oxide（ITO）electrode,the resultant GZO/Ag/GZO electrodes show lower sheet resistance of 10.66Ω·sq-1,higher average visible transmittance of 90.04%and superior figure of merit（Fo M）of 328Ω-1.When used as ITO-free transparent conductive electrode（TCE）for both classical fullerene and non-fullerene organic solar cells,comparable device performance or even better than that of those fabricated from ITO electrode is obtained.Given its low-cost,large-scale production accessibility,the GZO/Ag/GZO based electrode could be a good candidate for application in a wide range of Organic Electronics.2.Aluminum-doped zinc oxide AZO/Ag（Ti）/AZO,AZO/Ti/Ag/AZO,and gallium aluminum co-doped zinc oxide GAZO/Ti/Ag/GAZO multilayer transparent conductive films were deposited on the glass substrate by magnetron sputtering at room temperature.The effects of different Ti power co-sputtered with Ag and Ti as a seed layer for Ag films on the optical,electronic and structural properties of multilayer films were investigated.In addition,the influences of the oxide layer and Ti/Ag layer thicknesses on the photoelectric properties of multilayer films were further studied.The experimental results show that Ti as a seed layer changes the growth pattern of Ag.AZO/Ti/Ag/AZO and GAZO/Ti/Ag/GAZO films exhibit high photoelectric performance.Multilayer films with 50 nm GAZO and 12 nm Ti/Ag displayer low sheet resistance of 5.88Ωsq-1,high average light transmittance in the visible range of94.38%,and the figure of merit is above 1000Ω-1.The optical simulation results of non-fullerene receptor solar cell devices based on GAZO/Ti/Ag/GAZO electrodes are superior to those of ITO devices,so it is expected to be applied in the field of optoelectronic devices.3.Starting from the impact of two representative electrode interface layers——with perylene diimide（PDI）as the core and amino（PDIN）or amino N-oxide（PDINO）as the terminal substituent on the performance parameters of organic solar cell devices made from three different active layer materials,we found that the non-radiative recombination loss caused by different interlayers was significantly different,which was one of main reasons responsible for the differences in open circuit voltage of the devices.The analysis shows that the concentration of traps at the PDINO/active layer interface is relatively higher,and the photogeneration process is affected by the carrier trapping and de trapping release process.In contrast,devices based on PDIN interlayer have a more significant effect on reducing surface defect states,which effectively reduces the trap-assisted recombination.4.By comparing the solar cell devices based on a variety of classic fullerene acceptors and ITIC/Y-series non-fullerene acceptors,we demonstrate that the injection-dependent emission line-shape in organic semiconductors is primarily associated with a state-filling effect,where the extent of spectral blue-shift can be a strong indicator for energetic disorder.Molecular geometry with rigidity and coplanarity not only promotes preferential face-on stacking that narrows the energetic distribution of sub-gap states but also impedes torsional deformations of the conjugated backbone away from planarity,thereby facilitating largerπ-electron delocalization.These structural characteristics explain the seemingly contradictory high radiative efficiency of low-bandgap non-fullerene molecules,providing promising molecular design strategies to realize high-efficiency organic photovoltaics. 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