| In recent years,with the increasing environmental and energy problems,the search for new renewable energy has become the top priority of the scientific research.Reasonable use of renewable energy(such as solar energy,wind energy,hydropower,tidal energy,etc.)can not only solve the energy crisis,but also effectively solve the environmental pollution problems caused by the burning of fossil energy.As a renewable energy source,solar energy has the advantages of being universal,rich in content and large in development potential.And,the solar energy has been widely concerned by human beings.The conversion of solar energy into electrical energy is directly available to people in our daily lives.Among them,perovskite solar cells(PSCs)are one of the devices that convert solar energy into electrical energy.As a suitable photoelectric conversion device,PSCs have been widely concerned by the society due to their excellent performance.Its efficiency has grown from 3.8%in 2009 to 23.7%so far,and is expected to become the next new energy source.Generally speaking,the structure of PSCs is mainly ITO glass substrate/electron transport layer/perovskite light absorbing layer/hole transport layer/Au electrode.In PSCs,organic-inorganic hybrid perovskite materials are easily decomposed by the influence of moisture in the air.The most commonly used hole transport materials are organic small molecules Spiro-OMeTAD,DM,polymer PTAA and etc.These organic materials not only have their own degradation,but also have strong water absorption during use,which greatly affects the stability of the devices and shortens the service life.Therefore,the researchers proposed various solutions,such as:using all-inorganic perovskite materials,doped perovskite materials,encapsulating perovskite solar cells,and preparing inorganic hole transport layers to block moisture in the air from contacting perovskite materials.In order to improve the stability of the devices,we mainly do the following two parts:(1)Passivation of the perovskite film using oxygen,reducing surface defects,improving devices efficiency and stability;(2)Using inorganic hole transport materials to explore the best preparation conditions and improve devices stability.The specific experimental results are as follows:Part ?:Under laboratory conditions,we prepared the PSCs in a glove box to isolate the effects of moisture and oxygen in the air on the perovskite film.However,the preparation of perovskite film in the relatively anhydrous and oxygen-free conditions in the glove box greatly increases the synthesis cost of the device and hinders the industrial application of the device,so the preparation of the perovskite film in air will be more cheap,more attractive preparation method.In order to promote the industrial application of PSCs and simplifV the preparation conditions of the devices,in this chapter we mainly study the effect of oxygen in the air on the characteristics of perovskite film.Normally,The perovskite film was prepared in an argon glove box and then placed in a water-removing air condition to sufficiently contact the perovskite film with oxygen in the air to passivate defects on the surface of the film.The perovskite films placed at different times were prepared into planar structure PSCs,and the optimal oxidation time was obtained by comparing the J-V characteristic curves of the devices under different conditions.Through a large number of experimental comparisons,we obtained an optimal photoelectric conversion efficiency of 21.07%.More importantly,the devices has a relatively high stability,and the efficiency of the PSCs is reduced by 17%relative to the initial value after being placed in the air for 100 days.The results of this experiment show that oxygen helps to passivate surface defects of perovskites and improve the efficiency and stability of PSCs.Part ?:Despite the power conversion efficiency of PSCs reaching more than 23.7%,some issues such as cost and stability must be solved for commercialization.One of the most effective ways is to develop inorganic hole-transporting materials(HTMs)for PSCs.In the present work,CuInS2 quantum dots(CIS QDs)were synthesized using a modified hot-injection method and applied to PSCs as an HTM.A high PCE of 18.8%for the optimized solar cells with CuInS2 as an HTM was achieved,which was very close to that of a device with Spiro-OMeTAD as an HTM(19.2%).More importantly,the stability of solar cells with CuInS2 was significantly improved compared to those made with Spiro-OMeTAD.The PCE of CuInS2-based solar cells only decayed by 9%of the original value after 30 days,while the PCE of a Spiro-OMeTAD-based device decayed dramatically by 33%of the original value within 15 days.This work demonstrates that CuInS2 is a promising inorganic HTM for the fabrication of PSCs with high power conversion efficiency and long-term stability. |
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