Research On Functional Materials And Performance Improvement Of Devices In Perovskite Solar Cells

Perovskite solar cells have attracted extensive attention due to their high optical absorption coefficient,low exciton binding energy,and low material cost.In addition,the flexible and tunable band gap and high process compatibility make it suitable as the top cell of tandem cells,and the theoretical prediction of the photoelectric conversion efficiency of perovskite/silicon two-terminal tandem solar cells can reach 42%.At present,perovskite/silicon tandem solar cells are still in the stage of rapid development of efficiency,and there is still a lot of room for improvement in photoelectric conversion efficiency.The crystalline quality of the key functional layers and wide-bandgap perovskite absorber layers suitable for stacked devices is one of the main factors limiting the efficiency of stacked devices.In this paper,the carrier transport rate is improved by developing low-temperature atomic layer deposition Sn O₂,and additive engineering is used to improve the quality of perovskite films and reduce the non-radiative recombination energy loss.The use of high-density silicon heterojunction bottom cells to improve the utilization of photons in tandem cells.Thus,a high-performance PIN-type perovskite/silicon two-terminal tandem solar cell was prepared.The main research work of this paper is as follows:First,in the preparation process of the PIN-type electron transport layer C60/Sn O₂,the higher deposition temperature of Sn O₂ will destroy the perovskite absorber layer.This paper innovatively uses hydrogen peroxide as the oxygen source in the atomic layer deposition process.The Sn O₂ thin films with large area uniformity and excellent optoelectronic properties were prepared at low temperature by using its high oxidizing property.At the same time,due to the low deposition temperature,the temperature and TDMASn damage to the perovskite absorber layer during the deposition process is reduced.Based on a perovskite absorber layer with a bandgap of1.67 e V,a single-junction PIN-type wide-bandgap perovskite cell with C60/Sn O₂ as an electron transport layer achieves a V_OC of 1.240 V and an efficiency of 19.04%.Second,for high-efficiency high-efficiency perovskite/silicon two-terminal tandem solar cells.In this paper,a magnetron sputtering metal nickel target post-annealing process was developed to prepare a hole transport layer Ni Ox with excellent performance and suitable for large-area tandem batteries,and a double-layer transparent conductive film was prepared.The first layer of DC low-power sputtering was used to reduce the transparent conductivity The destruction of the underlying material during the deposition process of the film,the use of a double-sided small-textured silicon bottom cell to increase the photon utilization rate of the stacked device perovskite and silicon absorber layer.By optimizing the preparation process,a PIN-type perovskite/silicon two-terminal tandem solar cell with a V_OC of up to 1.85 V and an efficiency of 26.67%was finally obtained.And a 11.8 cm² large-area PIN-type perovskite/silicon two-terminal tandem solar cell with an efficiency of 23.07%.Third,single-junction flexible perovskite solar cells are usually prepared based on flexible polymer substrates,which have high water vapor permeability,so flexible perovskite cells have poor humidity stability.Aluminum acetylacetonate（Al（acac）₃）is introduced between the perovskite layers as the interface bonding layer.Since Al（acac）₃ is a typical cross-linking agent,on the one hand,it can form a unique spider web structure to block the penetration of water vapor.On the other hand,Al（acac）₃ can passivate perovskite,reduce perovskite defects,improve the crystal quality of perovskite,and significantly improve the stability and efficiency of FPSC.After optimizing the preparation process,20.87%efficiency and good long-term stability under atmospheric conditions（>50%relative humidity）.At last,we propose and design quasi-heteroplane（QHF-PSC）perovskite solar cells,which are designed from bilayer perovskite films.This novel structure of PSCs has excellent carrier separation ability,which effectively suppresses the non-radiative recombination of PSCs,thereby improving the open-circuit voltage and PCE.At the same time,by combining the wide bandgap perovskite layer with the narrow bandgap perovskite layer,the bandgap of the final perovskite absorber layer can be flexibly tuned by changing the film thicknesses of the narrow bandgap layer and the wide bandgap layer,the average V_OC is increased from 1.08V to 1.12 V,an increase of 40 m V,and the average J_SC is increased from21.50 m A/cm² to 22.20 m A/cm²,the average FF increases from 72%to77%.The main reason for the improved device performance is due to the fact that the heteroplane can increase the strength of the built-in electric field.At the same time,the bandgap of the perovskite absorber layer can be flexibly tunable in the range of 1.53 e V to 1.75 e V by combining a wide-bandgap perovskite layer with a narrow-bandgap perovskite layer.