Preparation And Application Of Narrow Bandgap Tin-Lead Alloyed Perovskite Photovoltaic Cells

At present,the perovskite solar cells have attracted extensive attention from researchers at home and abroad.After more than ten years of development,single-junction perovskite solar cells have reached a certified efficiency of 25.8%,which has very broad application prospects.In order to further break through the power conversion efficiency（PCE）,it is an effective method to assemble perovskite cells and other solar cells into tandem cells.Among them,organic-inorganic metal halide perovskite materials have the characteristics of tunable optical band gap（1.2-2.4 e V）,which provides a good light absorption window for the preparation of multi-junction tandem cells.Among various types of perovskite tandem cells,all-perovskite tandem cells have received much attention due to their perfect inheritance of the low-temperature solution processability and roll-to-roll compatibility of single-junction perovskite solar cells.This has drawn attention to narrow-bandgap Sn-Pb alloyed perovskite solar cells,with a certified PCE of 26.4%.However,such narrow-bandgap Sn-Pb alloyed perovskites have many urgent problems to be solved,including low crystalline quality,oxidation of Sn²⁺,interfacial defects,and energy loss due to energy level mismatch etc.,which resulted in the loss of PCE.Therefore,the preparation of high-quality Sn-Pb alloyed perovskite solar cells is a challenging and interesting research topic.This thesis focuses on the optimization of narrow-bandgap Sn-Pb alloyed perovskite,including interface modification and additive engineering,so as to improve the performance of narrow-bandgap Sn-Pb alloyed perovskite and further improve the PCE of Sn-Pb alloyed perovskite solar cells.This paper mainly includes the following contents:1.On the basis of the original narrow-bandgap Sn-Pb alloyed perovskite,the upper surface of the perovskite was modified with ethylenediamine dihydroiodide（EDAI）,and its concentration was optimized to obtain the best concentration.By modifying the upper surface of the perovskite at an optimal concentration,a higher-quality perovskite film was obtained.The PCE of modified Sn-Pb alloyed perovskite solar cells increased from 18.9%to 20.4%compared with that without EDAI passivator.2.On the basis of the above work,although the crystal quality of the thin film has been improved,the photoelectric performance of the device still needs to be further improved.The reason may be the oxidation of Sn²⁺and the energy band mismatch.Therefore,the additive tris（2,4-pentanedionato）gallium（TPGa）was added to the above perovskite precursor solution for optimization,which helps to obtain larger grain size and uniform distribution of perovskite microcrystalline films.At the same time,TPGa can also inhibit the oxidation of Sn²⁺,transform p-type doping into n-type doping,and make the energy level between perovskite absorption layer and electron transport layer better match,promote electron transport,and thus increase the PCE of the solar cells to 21.5%.In addition,the perovskite solar cells prepared by these comprehensive strategies can still maintain 80%of the initial efficiency after being aged in a nitrogen glove box for 1500 h.3.Finally,the four-terminal（4-T）tandem cells was prepared by stacking it with wide-band gap perovskite solar cells（1.74e V）as the bottom sub-cell,and its PCE was increased to 23.14%.Moreover,the steady-state output power（SPO）of the tandem device can maintain 5.03%efficiency after 100 s.