Study On The Performance Of Cs₂AgBiBr₆ Perovskite Solar Cells

Since the 21st century,people have faced two major problems:energy shortage and environmental pollution.The traditional fossil energy that has been relied on is not only non-renewable,but also produces exhaust gas harmful to human living environment.Therefore,it is necessary to develop new environmental energy.As one of the third generation of new thin-film solar cells,organic-inorganic metal halide perovskite solar cells have improved their efficiency rapidly in recent years,which has been comparable to commercial silicon-based solar cells,but their optical and thermal stability is poor and lead is contained.Using stable and low toxic all inorganic lead-free double perovskite Cs₂AgBiBr₆ as the light absorbing layer of the device has become a strategy that can be developed.Cs₂AgBiBr₆ has good stability in air and is less affected by temperature and humidity changes.However,the reported Cs₂AgBiBr₆ based solar cells have low efficiency.This is mainly because Cs₂AgBiBr₆ is an indirect band gap semiconductor with limited solubility in common organic solvents.The formed perovskite films have low crystallinity and defects.Based on this,we try to use a series of process optimization strategies such as interface modification engineering and additive engineering to improve the crystallization performance and film coverage of perovskite light absorbing layer and reduce the generation of trap states,so as to regulate the photoelectric performance of Cs₂AgBiBr₆ based double perovskite solar cells.The main work contents are as follows:（1）In order to adjust the energy level matching degree of the device and improve the carrier mobility,we used molybdenum disulfide（Mo S₂）nanoflakes as the interface modification layer to improve the photoelectric performance of Cs₂AgBiBr₆ perovskite solar cells.Subsequently,perovskite solar cells with Mo S₂ nanoflakes,PTAA and pure Cs₂AgBiBr₆ were compared.The valence band energy level of Mo S₂ nanoflakes stripped by ultrasonic liquid phase is well matched with that of the perovskite layer and the carbon layer,which accelerates hole extraction and improves the carrier migration efficiency in perovskite solar cells.In addition,the addition of Mo S₂ nanoflakes significantly improved the crystallinity of the perovskite layer and the morphology of the film.The PCE of devices based on Mo S₂ nanoflakes reached 4.17%,which was significantly higher than that of devices based on PTAA（3.21%）and control devices（2.61%）.In addition,the efficiency of devices containing Mo S₂ nanoflakes is only reduced to 92%after 23 days of storage in air,which has excellent stability.（2）In order to improve the crystallinity and film morphology of Cs₂AgBiBr₆,cobalt dibromide（Co Br₂）was doped into the perovskite precursor.The Co Br₂ content was added to the perovskite precursor by setting the concentration gradient according to different mass percentages.It is found that the quality of perovskite film can be improved by introducing an appropriate amount of Co Br₂ into the precursor.With the addition of2 wt%Co Br₂,the PCE of the device reached 2.94%and the J_sc was 4.35 m A cm^-2;V_ocis 1.14 V;FF is 0.59,which is the best device performance in this group of experiments,reduces the generation of leakage current in the device and charge recombination.It is proved that adding an appropriate amount of Co Br₂ can improve the photoelectric performance of Cs₂AgBiBr₆ perovskite solar cells.（3）Adding cellulose acetate（CA）as an additive to Cs₂AgBiBr₆ precursor can improve the quality of perovskite film.The abundant carbon oxygen double bond functional groups in CA interact with the under coordinated cations to regulate the crystallization rate of the films and improve the solution viscosity.In this experiment,the PCE of the device with CA is 2.87%,and the J_sc is 5.08 m A cm^-2;V_oc is 1.03 V;FF is 0.55,which is the best device performance in this group of experiments.The best PCE of pure Cs₂AgBiBr₆ based PSC is 2.66%and J_sc is 3.99 m A cm^-2;V_oc is 1.03 V;FF is0.54.In addition,the efficiency of CA based devices only decreased to 85%after 23days in air.Compared with pure Cs₂AgBiBr₆ based PSC,the efficiency decreased to80%,indicating that the device containing CA has better stability in atmospheric environment.