Preparation And Optoelectronic Properties Of Perovskite Solar Cells With Hole Additives

Organic-inorganic hybrid perovskite solar cells?PSCs?are considered the most promising competitors for silicon solar cells because of their excellent optoelectronic properties,such as broad absorption spectrum,high charge mobility and long carrier diffusion length.However,there are some problems remained in PSCs,such as large bandgap energy causing no near-infrared light absorption,high energy consumption,expensive hole-transport materials,toxic,poor stability.Our research is mainly about how to improve efficiency and cost effective of PSCs by using some additives.There are two contents in my paper.One is to introduce additives into the perovskite light-absorbing layer to form bulk heterojunctions,which could increase device efficiency in bi-layer PSCs.The other is to introduce carbon powder additives into the Ti₃C₂,which has been used as composite back-electrode.By introducing these additives,we further explore the function and demonstrate mechanism in PSCs.The specific contents are as follows:?1?Self-designed cognition experiments were conducted to improve hole extraction efficiency,as well as to deeply understand the work principle of additives.A common hole transport material,2,2',7,7'-tetrakis[N,N-di?4-methoxyphenyl?amino]-9,9'-spirobifluorene?Spiro-OMeTAD?,was used as an additive for bulk heterojunction PSCs?BHJ-PSCs?.Results showed that the PCE of mesoporous BHJ-PSCs?M-BHJ-PSCs?was enhanced by more than15%when an extremely low concentration of Spiro-OMeTAD additive was added.However,the crystallization of perovskite was hampered and recombination risk increased when grain boundaries increased in the perovskite layer.Planar BHJ-PSCs were fabricated to further investigate the role of additives.In comparison with those in planar BHJ-PSCs,hole extraction efficiency and diffusion length significantly improved in M-BHJ-PSCs due to the transport path and relay effects formed by Spiro-OMeTAD additives.Subsequently,exact functions and new work principle of additives in BHJ-PSCs were proposed.?2?Two-dimensional transition metal carbide Ti₃C₂ with good conductivity was prepared from Ti₃AlC₂ and used as counter electrode of the PSCs.Efficiency of the device was not good enough due to the disconnections between the Ti₃C₂ film and perovskite layer and also the disconnection betwenen Ti₃C₂ particles.After adding the carbon powder additive in Ti₃C₂,Ti₃C₂ and carbon powder interpenetrate each other.At the same time,the adhesion between the Ti₃C₂/C counter electrode and perovskite layer is also enhanced.Therefore,the internal resistance of electrode and the interfacial resistance are reduced and the efficiency of whole devices has been promoted.