| Organic/polymer solar cells is one of the most promising solar cell technologies in the future due to their abundant active layer materials,light-weight,low cost and large-area production.In recent years,researchers have focused on non-fullerene polymer solar cells due to the rapid advancement of non-fullerene acceptors that possessing adjustable in absorption spectra and energy levels.To realize a highly efficient non-fullerene solar cells,it is the key to improve the energy conversion efficiency by constructing a photoactive layer with a donor and an acceptor possessing complementary light absorption.Therefore,the development of a wide band gap conjugated polymer donor becomes a hot spot in the field of solar cells.The wide band gap conjugated polymer constructed by the imide-functionalied benzotriazole(TzBI)electron-withdrawing unit has good photoelectric properties and has a large modification space in both the main chain and the side chain,and is a potential material.In order to further obtain more efficient wide bandgap conjugated polymer material,this paper focused on the construction of a series of wide bandgap conjugated polymers around alkoxy-substituted imide-functionalied benzotriazole electron withdrawing units:In the second chapter,alkoxy-substituted imide-benzotriazole electron with-drawing unit(TzBI-O)is synthesized by introducing the alkoxy chain into the imide of the TzBI electron-withdrawing unit.The dithiophene unit constitutes the polymer PTzBI-O.The introduction of oxygen atoms red shifts the absorption spectrum and lowers the HOMO level of polymer.The pre-aggregation of the polymer in the toluene solvent causes red-shifted in the absorption spectrum of the PTzBI-O pure film and the N2200 pure film.Whether using halogenated solvents(toluene)or non-halogenated solvents(chloroform and chlorobenzene),the performance of the device based on PTzBI-O:N2200 is higher than PTzBI:N2200,mainly exhibiting the increased short-circuit current density and open circuit voltage.The efficiency of the device processed by toluene can be up to 7.91% owning to pre-aggregation,while the efficiency of the device processed by chlorobenzene is 7.39%,and the efficiency of the device processed by chloroform is only 6.58%.This work provides an important reference for the development of new wide bandgap polymer donor materials and green processing toward all polymer solar cells.In the third chapter,based on the polymer PTzBI-O(referred to as Ph00 in this chapter),a series of terpolymer donor materials were synthesized by introducing the third component BDTP units instead of BDDT units.The effect of the content of BDTP unit on the optical/electrical properties of the polymer material and the photovoltaic performance were investigated.As the content of BDTP increases,the absorption spectrum of the polymer gradually become blue-shifted,and the HOMO level gradually decreases.Based on the terpolymer: ITIC non-fullerene solar cell device,as the content of BDTP unit increasing,the open circuit voltage in the device increases gradually,and the fill factor first increases and then decreases.The terpolymer Ph50 exhibited photovoltaic performance with a PCE of 8.55%,higher than the device efficiency of the binary polymers Ph00(7.42%)and Ph100(7.62%),the increase in the fill factor based on the terpolymer device is attributed to its more balanced charge mobility.This work proved that ternary copolymerization is an effective strategy to improve power conversion efficiency.In the fourth chapter of this paper,in order to improve the inter-molecular packing in the active layer,we developed two branched polymer acceptors P3F-0.5 and P3F-2 by introducing the truxene as a nuclear unit in the main chain of the traditional linear polymer acceptor N2200 and the polymer PTzBI-O was selected to construct all-polymer polymer solar cells.The introduction of units has an effect on the crystalline nature of the polymer acceptor,the packing between the molecular chains,and the overall device performance.The DSC test showed that the crystallization ability of the polymer decreased with the increase of the content of truxene.However,the reflection peak of the blended film(100)of the branched polymer acceptor in the GIWAXS diagram showed a narrower azimuthal integral distribution,indicating that the branch polymer acceptors can improve the stacking of molecular side chains.The overall polymer solar cell device based on PTzBI-O:P3F-2 has an efficiency of 8.0%,which is higher than the device efficiency of 6.7% of PTzBI-O:N2200.This is the first time that branched polymer acceptor materials have been used in all-polymer solar cells,providing a new strategy for the design of polymer acceptor materials. |
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