Preparation And Performance Of Low-Temperature And High-efficiency Carbon-Based Perovskite Solar Cells

In this world,the need for clean energy has continuously increased and photovoltaic industry is developing fast.In recent years,emerging perovskite solar cells(PSCs)are considered to be one of the most promising new thin-film solar cells because of their stronger light absorption,better technology repeatability and higher power conversion efficiency(PCE).Up to now,their certified efficiency up to 25.2%has been achieved.However,most traditional PSCs including expensive hole transport material and metal electrode need high-temperature process,which greatly increases the cost of raw material and operation.Serious non-radiative recombination of carriers and a large number of defect state at the interface would break photoelectric performance of the device.Based on the above problems,this paper replaces hole transport layer and metal electrode with carbon electrode to fabricate planar carbon-based PSC(C-PSC)and uses this structure as a basis.On one hand,adopt the alkali metal hydroxide interface engineering to explore its impact on electron transport layer(SnO2),inorganic perovskite layer(CsPbI2Br)and overall device performance.On the other hand,integrate device at room temperature and introduce PEG into the perovskite/carbon interface to explore its mechanism on this interface and impact on performance of room temperature device.And then apply this process to preparation of flexible devices.The specific details are as followed:(1)Using alkali metal hydroxides(KOH,NaOH)as interface modifiers,SnO2,alkali metal hydroxides,and CsPbI2Br are sequentially spin-coated on the ITO conductive substrate,a carbon-based device is integrated after coating carbon layer.Characterization finds that the alkali metal hydroxide layer not only reduces work function and surface tension of the SnO2 layer,but also improves the quality of CsPbI2Br film and accelerates the electron transfer between CsPbI2Br and SnO2.More importantly,K+can effectively suppress halide ion migration and vacancy defect formation by forming KBr-like compounds.The PCE of carbon-based CsPbI2Br PSC reaches to 11.78%(0.09 cm2)and 9.34%(1.00 cm2),respectively.Moreover,improved stability and reduced hysteresis of devices have been realized.(2)We prepare SnO2,perovskite and carbon electrode at room temperature respectively,and explore the room-temperature integration process of planar C-PSC.A low-cost polyethylene glycol(PEG)is introduced as an interface passivation layer,in which the lone electron pair of oxygen atom coordinated with uncoordinated Pb2+ to reduce the defect state at the perovskite interface.In addition,hygroscopic PEG can adsorb water molecule on the surface to prevent the destruction of the perovskite structure.Research indicates that the device efficiency passivatied by PEG increases by nearly 50%and reaches to 14.54%,which still keeps 90%of the initial value in humid air for 20 days.Moreover,the efficiency of flexible C-PSC prepared by the same process exceeds 10%.