High Performance Counter Electrode Based On The Composite Of Lamellar Material And CuS In Quantum Dot Sensitized Solar Cells

Quantum dots（QDs）are one of zero-dimensional materials with many characteristics,such as adjustable band gap,good photostability and multi-exciton effect.The theoretical efficiency of quantum dot sensitized solar cells（QDSCs）can reach 44%,which is thought the most promising third-generation solar cells.The main function of counter electrodes（CEs）in QDSCs is that transfer the electron to the interface between electrolyte and CE and reduced the electrolyte.The ideal CEs materials need larger specific surface area,higher catalytic activity and good electronic transmission performance to contact with more electrolyte,restored holes and transmit the electron.At present,the most common CE is Pt.However,as a precious metal,Pt has high price due to its scarce reserves.Metal sulfide,with large specific surface area,good stability,high electrocatalytic activity and low cost,is a powerful substitute for Pt.Graphite carbon nitride（g-C₃N₄）has a large specific surface area,excellent stability and lamellar structure which similar to it of graphene.Two-dimensional transition metal carbide/nitride（MXene）is a new kind of lamellar material,which has the structure and performance of graphene.In this paper,g-C₃N₄was prepared by melamine,Cu S particles were grown on g-C₃N₄sheet via low-temperature solid-state method.The g-C₃N₄/Cu S composite CEs had significantly reduced interface impedances,greatly improved interface catalytic activities and enhanced stabilities.The CN/10Cu S CE has the best performance,of which the J_scwas 23.37m A/cm~2and the PCE was 5.05%.Ti₃C₂was prepared by Li F and HCl,and pure Ti₃C₂CE was prepared by uniform gel mechanism.Cu S with different periods were deposited via SILAR method to prepare Ti₃C₂/Cu S（QDs）composite CE.When the deposition period is 7,TC-7Cu S CE,with an efficiency of 4.68%,has the best performance,interfacial catalytic activity and stability.Compared with the two composite CEs,g-C₃N₄/Cu S CEs have the simpler preparation method,the larger open-circuit voltage,the better stability and the better photoelectric performance with CN/10Cu S.Ti₃C₂/Cu S（QDs）CEs have better catalytic reduction,higher average efficiency,larger short-circuit current and smaller band gap.