Strategies Towards Improve The Efficiency And Stability Of Inverted Perovskite Solar Cells

Perovskite solar cells is one of the most promising technologies to realize commercialization among various next-generation solar cells.Since the Japanese scientists Miyasaka et al.introduced perovskite materials into dye-sensitized solar cell in 2009,perovskite solar cells have made rapid progress in terms of photoelectric conversion efficiency and device stability,and there certificated efficiency was as high as 25.2%.This record efficiency is much better than the commercially available copper-indium-gallium-selenium solar cells and cadmium telluride solar cells,and is comparable to crystalline silicon solar cells.In the development of perovskite solar cells,the researchers have focused on the improving the efficiency and stability of solar cells.In order to address these issues,interface engineering,additive engineering,anti-solvent engineering,and device structure optimization,and so on are performed.This thesis is based on the inverted perovskite solar cell as the structural foundation,with the purpose of improving the efficiency and stability of the device,and we have achieved the following results:（1）We prepared a patterned ITO substrate with a hexagonal honeycomb structure to improve the optical and electrical properties of conductive glass substrate.The hexagonal honeycomb ITO substrates were fabricated by combining the polytetrafluoroethylene microsphere template method and magnetron sputtering technology,and are successfully used in the inverted perovskite solar cells.Compared with the traditional ITO substrate,the hexagonal honeycomb ITO can partly scatter the incident light and change the propagation path of light in the device,thereby increasing the optical path and improving the absorption efficiency of the incident light.On the other hand,it can increase the contact area between NiO_xand the perovskite layer,thereby enhancing the charge extraction capability of the device.Compared with the traditional ITO substrate,the photovoltaic device used hexagonal-tiled ITO substrate with ITO/NiO_x/MAPbI₃/PCBM/BCP/Ag structure exhibited a maximum PCE of 18.2%,with the V_ocof 1.06 V,J_scof 21.65 m A cm^-2and FF of 0.791,which showed an encouraging improvement of over 7.2%in the J_scand a 7.4%enhancement in the PCE compared with the traditional ITO substrate.This work provided an innovative approach to improve the photon management and capture in perovskite solar cells.（2）We combined an anti-solvent strategy and additive engineering to improve the crystal quality of perovskite films,and enhance the efficienty and long-term stability of the device.This method involved in chlorobenzene solution containing methylamine gas as a new type of antisolvent to treat the FACs-based perovskite films.Based on this method,we fabricated the high-quality FA_0.85Cs_0.15Pb(Br_0.15I_2.85)films with the preferred orientation of（101）.The modified films showed a lower defect density and a better hydrophobic performance.Meanwhile,the perovskite films became dense and uniform.Based on this modified strategy,the PCE was up to 19.6%.It showed an encouraging improvement of over13.95%enhancement compared with the traditional antisolvent strategy.The high-efficiency devices could maintain over 95%or 88%of their initial PCEs after 500 h under continuous light soaking or thermal aging in dark at 85℃in a N₂filled glove box,respectively.These results provided an approach to control and adjust the grain size,morphology and hydrophobic performance of perovskite films.（3）We found a new way to improve the efficiency and stability of perovskite devices used the gradient CsPbBr₃/CsPbI₂Br all-inorganic perovskite films.In this method,a more stable CsPbBr₃perovskite thin layer was thermally evaporated on the surface of the CsPbI₂Br perovskite film.Our study demonstrated that the CsPbBr₃was only enriched on the sample surface,and can improve the charge transfer at the interface and inhibit the electron and hole recombination.The PCE of CsPbI₂Br perovskite solar cell with a 1 cm²area was up to10.99%,which showed an encouraging improvement of over 17%enhancement compared with the standard device.At the same time,the stability of the Cs Pb I₂Br film and device has been improved.The CsPbI₂Br solar cell with 4 nm thermally evaporated CsPbBr₃showed better stability under the double 85 testing standard;and the device has better stability under the light aging test at 60℃.