Microscopic Photovoltaic Mechanism And Device Optimization Of Hybrid Solar Thin Films Based On Microscopic Imaging Technology

Along with the development of science and technology,the confliction between the increasing demand for traditional energy sources and the limited available traditional energy on the earth is becoming more and more severe.This has led to unprecedented development of new green and renewable energy sources.Among them,solar energy,as an inexhaustible source of clean energy,has been widely concerned all over the world,and thus the research on solar cells has attracted significant attentions from researchers.The International Energy Agency?IEA?predicts that by 2050,the global electricity consumption will exceed 50 trillion kWh,twice as much as in 2014,and the share of solar power will increase from 2%in 2014 to 17%.At the same time,in response to the global smog and haze,other climate deterioration and ecological sustainable development crisis,solar power technology will obtain a huge market.At present,a large number of attempts have been made in various materials under study,including commercially silicon-based solar cells,dye-sensitized solar cells,conductive polymer-based composite solar cells,and researched perovskite solar cells.The organic-inorganic hybrid perovskite is becoming a candidate material for high-efficiency thin film photovoltaic materials due to its excellent photoelectric properties such as direct band gap,high absorption coefficient,long carrier diffusion length and low temperature process performance.Perovskite solar cells have achieved unprecedented development in photoelectric conversion efficiency.Since the publication of the first dye-sensitized solar cell using perovskite as a material in 2009,the reported efficiency has ranged from 3.8%to over 23%.Despite the rapid performance of perovskite solar cells?PSCs?,there are still some problems.The stability of perovskite devices remains a major obstacle to the commercialization of PSCs in the future.Therefore,a variety of characterization techniques are needed to understand the optoelectronic properties of the perovskite film in order to better improve the efficiency and stability of the PSCs.In this paper,we studied the photoinduced charge separation and electron transfer process of Ag nanoparticles and conductive polymer PCPDTBT composite films using a Scanning Kelvin probe microscope?SKPM?.Charge separation was observed at resolutions of several to tens of nanometers,which provided a reliable basis for the subsequent application of atomic force microscopy to characterize perovskite films.In perovskite solar cells,each layer plays a different and crucial role in the PSCs.Various semiconductor organic and inorganic materials can be effectively used as an electron or hole transport layer of PSCs.However,in addition to their role in the final photovoltaic devices,their direct effects have rarely been reported.Therefore,we used a SKPM to verify the charge transport properties of SnO₂ and NiO_x.The change in surface potential measured before and after illumination directly indicates whether these carrier transport materials extract electrons or extract holes.This work undoubtedly provides us with a versatile and effective way to distinguish the carrier transport capacity of electron or hole transport materials.The carrier type has been undisputedly clarified,and the best carrier transport materials suitable for perovskite solar cells could then be selected.Doping is a powerful technique for carrier concentration modulation in semiconductors for microelectronic devices and is widely used in the solar cell industry.Doping in PSCs is also an effective way to improve the performance of solar cell.Here,the properties of perovskite-doped films with different Mn/Pb ratios were systematically studied.The efficiency of solar cells with 0.2%manganese was significantly improved compared to devices without manganese.Then,we used SKPM,electrostatic force microscope?EFM?,conductive force microscope?C-AFM?to study the surface potential,surface charge and surface current of different Mn doped films.This demonstrates that the multi-functional scanning probe microscope combined with a variety of thin film characterization techniques provides an effective tool for studying the role of doping in PSCs.Three-dimensional perovskite solar cells have received great attention due to their extremely high energy conversion efficiency and ease of preparation.However,their environmental instability is still a major commercial challenge.Compared to three-dimensional perovskites,long-chain organic hydrophobic cations commonly used in two-dimensional materials give them greater humidity stability.Although two-dimensional perovskite solar cells have excellent stability,they have relatively poor photovoltaic performance.Here,two-dimensional materials?F-PPEAI?are used to form hybrid 2D and 3D heterostructure perovskite films,which greatly improves the performance and stability of perovskite solar cells.In the 2D/3D heterostructure,the hydrophobic quasi-two-dimensional phase is vertically located between the perovskite grains,forming a grid-like structure,tightly enveloping the grains,and plays a significant passivation effect.2D/3D perovskite solar cells improve the stability of the device while maintaining high efficiency?20.1%?.This work presents the possibility of a more controllable heterojunction PSCs.This facilitates the timely commercialization of perovskite solar cells.