Research On Perovskite Solar Cells With Broad Spectral Response

Perovskite solar cells(PSCs)have achieved incredible development in the past few years,and the certified power conversion efficiency(PCE)of PSCs has been obtained 25.5%,which is comparable to that of silicon-based solar cells.Although PSCs have achieved rapid development,the efficiency of converting solar energy into electricity is still to be increased.Its conversion ability is mainly related to the spectral utilization rate:low-energy photons cannot be absorbed by PSCs while high-energy photons are not efficiently used.The AM 1.5 sunlight can be used in the spectrum wavelength range of 280-2500 nm.However,the commonly used high-efficiency lead-based perovskite materials have a large band gap.It only can absorb a small part of the ultraviolet and visible light,accounting for only 45-50%of entire solar spectrum.Therefore,further broadening the utilization of near-infrared light and improving the effective utilization of ultraviolet light of PSCs has become urgent issues for PSCs.My research during my Ph.D period is to expand the near-infrared light spectral response and improve the utilization of ultraviolet light.The efficient and highly stable PSCs with broader spectral response can be achieved by using the synergistic effects of inorganic semiconductors,organic heterojunctions and gold metals.(1)Firstly,hydrophobic Cu₂Cd_xZn_1-xSnS₄(CZTS:Cd)films and gold nanorods(Au NRs)were successfully introduced into the PSCs.The co-introduction of CZTS:Cd films and Au NRs simultaneously broadened and enhanced the near-infrared spectral response of the device.The PSCs integrated with CZTS:Cd and Au NRs extended the photoelectric response to 900 nm.The efficiency of the device was increased from 19.30%to 21.11%.The modified PSC device also showed highly improved humidity stability.This work shows that the perovskite/inorganic semiconductor integrated device structure is a promising strategy to expand and enhance the NIR response of PSCs.(2)Secondly,in order to further expand the near-infrared photoelectric spectral response of PSCs,PBDB-TF:BTP-4Cl organic heterojunction and Au NRs were introduced into PSCs at the same time.The spectral response of PSCs was broadened to 950 nm.To improve device stability,the Mo O₃ was applied as the hole transport layer(HTL).After adopting this device,the PCE was significantly increased from16.67%to 21.55%,which was the optimum among the reported organic/perovskite hybrid solar cells and the devices employing Mo O₃as the HTL.The device under standard sunlight for 1000 h still maintained 70%of the initial PCE.(3)Thirdly,to further increase the spectral response of PSCs and improve the ultraviolet light utilization of the device,the new COTIC-4F:PC₆₁BM:PBD7-Th ternary organic heterojunction layer,gold nanotriangular(NTs)and efficient three-doped CsPbCl₃:Yb³⁺,Ce³⁺,Cr³⁺were successfully integrated on the PSCs,thereby extending the photoelectric response of the device to 1100 nm.Finally,the PCE was significantly increased from 19.23%to 21.34%,which is one of the most efficient hybrid organic/PSCs reported.The improved PSC device also showed highly improved humidity and light stability.This work has important guiding significance for improving the collection of ultraviolet and near-infrared light.(4)Finally,the property of flexible,large-area and semi-transparent devices had been significantly increased.Gold nanostar(Au NSs)and Sn O₂ were successfully introduced into PSCs.This design increased the capture of light and the carrier transport of the device.As the thickness of the absorption layer is 250 nm,the PCE of the device was increased from 15.34%to 18.50%,and the maximum enhancement factor reached 20.60%.As the thickness of the absorption layer is 400 nm,the PCE reached 20.06%.More importantly,flexible,large-area and semi-transparent PSC was also successfully synthesized.After 100 times of bending,the efficiency of the flexible devicemaintained more than 90%of its initial PCE.Our work has important guiding significance for obtaining ultra-thin,efficient,flexible and semi-transparent PSCs.