Study On High-Performance Perovskite Photoelectric Devices Based On Bulk Modification

In recent years,perovskite materials have attracted extensive attention due to their excellent photoelectric properties.Asides from remarkable success in photovoltaics,they are highly promising in other optoelectronic fields,such as photodetectors,light-emitting diodes,and field-effect transistors.Although the above research is based on different device structures,the fabrication of perovskite films with high crystalline quality and low defect state density is the key to obtain high-performance devices.Therefore,the further development of the film-forming technology of perovskite materials and the improvement of the crystalline quality of perovskite films are issues worthy of consideration and attention.The work of thesis focuses on the fabrication of a perovskite absorber layer with high crystalline quality and low defect state density through bulk optimization of the perovskite absorber film,and then obtains the perovskite optoelectronic device with excellent performance,and has achieved the following results:(1)A new p-type?-conjugated ladder-like polymer P-Si has been designed and synthesized for the preparation of organic-inorganic hybrid perovskite films.Our investigation reveals that this?-conjugated ladder-like polymer system decorated with hydrophobic alkyl chains and siloxane chains is supposed to improve the surface morphology and crystallinity of the perovskite films to reduce defect state density and enhance the device stability.In addition,the P-Si with a suitable highest occupied molecular orbital energy level can act as a hole transport medium between the perovskite and the Spiro-OMe TAD to enhances the hole transport ability.Under the optimal addition conditions,we can obtain the champion device which can present as high as 21.5%power conversion efficiency(PCE)with 21.3%steady-state PCE.Further research shows that the P-Si modified device has excellent long-term stability and photoelectric stability.This work provides a new?-conjugated ladder-like polymer to fabricate good quality organic-inorganic hybrid perovskite films to obtain high-performance organic-inorganic hybrid perovskite solar cells.(2)A modified two-step multiple spin-coating method is used to prepare all-inorganic perovskite films.Our investigation reveals that by introducing dimethyl sulfoxide(DMSO)as an additive in the precursor solution,a high crystalline quality CsPb(I_xBr_1-x)₃(0<x<1)perovskite film can be obtained.It is found that,the introduction of a small amount of DMSO(2 vt%)in Cs Br/Me OH solutions can improve the surface morphology and crystalline quality of the perovskite film and effectively reduce its defect state density.Under the optimal addition conditions,we can obtain the champion device which can present as high as 13.27%PCE with 12.5%steady-state PCE.Especially,the devices exhibit superior stability in ambient condition without encapsulation.This work provides a new way to fabricate good quality all-inorganic perovskite films to obtain high-performance all-inorganic perovskite solar cells.(3)A urea-ammonium thiocyanate(UAT)molten salt modification strategy has been developed for the preparation of CsPb I₃ films.Our investigation reveals that the CsPb I₃ film with high crystalline quality can be obtained by fully release and exploit coordination activities of SCN^-.Studies have found that UAT is derived by the hydrogen bond interactions between NH₄⁺in NH₄SCN and urea.By optimizing the raw material ratio and addition amount of UAT,we can obtain the champion device which can present as high as 20.0%PCE with 19.2%steady-state PCE.Subsequent stability test results show that the device prepared under this condition did not show any performance degradation after 1000 hours of continuous operation.The above-mentioned performance is one of the highest records reported so far for all-inorganic perovskite solar cells.This work provides a new strategy for the preparation of high-quality CsPb I₃ films to obtain high-performance all-inorganic perovskite solar cells.(4)A spin-coating thermal-pressed strategy was developed for the preparation of CsPb I_xBr_3-x quasi-single-crystal(QSC)films.Our investigation reveals that the QSC film with high crystallinity and uniform orientation of CsPb(I_xBr_1-x)₃ can be obtained by hot pressing the traditionally annealed perovskite film.By adjusting the pressure parameters,perovskite grains with a lateral size close to 40?m can be obtained,which greatly reduces the grain boundaries and defect state density of the perovskite film.With the significant decrease of the defect state density,the perovskite film obtained a longer carrier lifetime and a larger two-photon absorption coefficient,which is better than the previous reports of CsPb(I_xBr_1-x)₃ quantum dots and thin films.Further studies have shown that the QSC film can achieve single/two-photon response in the 532 nm and 1030 nm bands,respectively.This work provides a new strategy for the preparation of high crystalline quality all-inorganic perovskite QSC films to obtain a dual-mode photodetector with excellent performance.