| Perovskite solar cells(PSCs)have attracted widespread attention due to their remarkable photoelectric properties,excellent power conversion efficiency(PCE),and low-cost manufacturing.Currently,PSCs have received a certified PCE of up to 25.5%,and are considered as a strong competitor of many advanced photovoltaic(PV)technologies,indicating potential commercial applications.Compared with mesoporous PSCs,n-i-p planar heterojunction PSCs are hailed as the most promising PV technology due to their remarkable optoelectronic properties,good cost-effectiveness,and low-temperature processing.However,planar perovskite absorbers tend to suffer from additional optical losses due to insufficient light harvesting and deteriorate device performance.In addition,the hetero-interface charge recombination and hysteresis in planar PSCs are also the key factors leading to a poor PV output of the devices.Accordingly,this work will combine solution spin coating,interface passivation and solvent engineering to improve the PV performance of planar PSCs.1)A novel“hillocks”-like random-textured perovskite(HRT-perovskite)was constructed to enhance the light harvesting of planar PSCs;2)the electronic properties and interface quality of a tin oxide(Sn O2)electron-transporting layer(ETL)were improved by introducing 2-hydroxyethyl modified gold nanostars(HEPES-Au NSs)into a commercialSn O2colloidaldispersion;3)the film quality of perovskite and hysteresis behavior of planar device were improved by adjusting the solvent environment.In addition,the crystallization kinetics of perovskite and hetero-interface carrier transport/recombination mechanism were systematically explored by using several advanced measurements and characterization.The main contents are as follows:(1)To alleviate the optical losses of planar PSCs,a novel HRT-perovskite absorber is developed using a facile chlorobenzene(CB)anti-solvent assisted spin-coating approach.The crystallization kinetics and formation mechanisms of CB-induced HRT-perovskite absorbers are systematically explored,allowing us to gain insights into the role of CB,i.e.an appropriate volume of CB promotes the formation of a porous MAI-Pb I2-DMSO intermediate structure.The results show that the porous nature of the intermediate film provides sufficient space for the coming lattice reconstruction and structure expansion during crystal growth,thus effectively improving the film and surface/interface quality,and finally enhancing the optoelectronic properties of the perovskite absorber.In addition,the HRT-perovskite exhibits excellent light-trapping capability and carrier mobility,due to its optimized surface roughness and longitudinally ordered grain boundary distribution.As a result,the efficiency of planar PSC(?400 nm-thick HRT-perovskite)was increased to 20.03%with a short-circuit current density(Jsc)of 22.98 m A cm-2,a fill factor(FF)of 77.53%and an open-circuit voltage(Voc)of 1.12 V.The processing exhibits very high reproducibility with 20 individual devices fabricated in one batch,achieving an average PCE of 19.00%.(2)We propose a simple and effective strategy to simultaneously improve the electronic properties and interface quality of a Sn O2ETL by introducing HEPES-Au NSs into a commercial Sn O2 colloidal dispersion.Owing to the synergistic effects of the Au NS plasmonic structure and 2-hydroxyethyl(HEPES)modifier,the modified ETLs exhibit higher conductivity and greater efficiency in the extraction/transfer/collection of electrons than conventional Sn O2 ETLs.Moreover,the chemical bond interaction between HEPES-Au NSs and perovskite enhances the affinity of the Sn O2/perovskite interface,which improves the nucleation and crystallization kinetics of the perovskite,thus producing a high-quality absorber and superior absorbance.Furthermore,the HEPES adsorbed onto the Sn O2 surface effectively passivates perovskite-related trap states,suppressing the non-radiation recombination and leakage current,thus improving the PV output and hysteresis behavior of the modified device.As a result,the PCE of the modified planar PSCs is significantly better than that of the original Sn O2-based planar devices,with negligible hysteresis.In addition,the functionalized devices without encapsulation also shows good stability and reproducibility.(3)To achieve efficient and non-hysteresis planar PSCs,we systematically explore the influence of solvent environment on the precursor configuration,perovskite crystallization kinetics,and photoelectric properties of the PSCs.Dimethyl sulfoxide/dimethylformamide(DMSO/DMF)blend solvent(BS)promotes the construction of porous"rod"precursor film,which provides sufficient space for lattice expansion and orientation selection during perovskite growth,thus preparing high-quality perovskite absorbers with high crystallinity.Moreover,DMSO/DMF BS also induces the formation of amorphous lead chloride(Pb Cl2)and stores it in the final perovskite film,effectively passivating perovskite defects,extending carrier lifetime,and significantly improving device performance.In addition,we also introduce formamidinium iodide(FAI)into methyl-ammonium iodide(MAI)/iso-propyl alcohol(IPA)solution,and evaluate the effect of different mixed-cation environments on perovskite morphological characteristics,surface/interface properties,and solar cell hysteresis behavior by optimizing the loading time.Ultimately,a DMSO/DMF-based planar PSC is prepared with reverse efficiency of 19.69%and forward efficiency of19.54%. |
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