Design And Preparation Of The Bottom Cell For Perovskite-Crystalline Silicon Tandem Solar Cells

Perovskite-crystalline silicon tandem cell is a new generation of photovoltaic cell combined with thin film cell and crystalline silicon cell,which has the advantages of wide spectrum absorption and higher photoelectric conversion efficiency(>30%),and has become a research focus in recent years.At present,the research of this cell is more about the optimization of perovskite solar cell(top cell),and less about crystal silicon cell(bottom cell).In this paper,Silicon Heterojunction solar cells(SHJ solar cells)were used as target bottom cells to optimize the performance of tandem cells,including the effects of crystal silicon surface roughness on bottom cell performance and perovskite absorption layer.The properties of the front/back bonded bottom cell structures are different,and the optimization of i-a-Si:H film on crystal silicon substrate on i-a-Si:H/c-Si interface passivation performance is studied.The main conclusions are as follows:1、Three kinds of N-type monocrystalline silicon with different front surface texture were prepared.The average surface pyramid size was 0μm(polished)/0.7μm/1.8μm,and the surface roughness(Ra)was 20nm/55nm/135nm.Under the 800-1180nm reflectance(R)to an average of 44.10%/15.78%/16.27%,after the pyramid on the surface of the average size of 1.8 microns.Under the same amorphous silicon film deposition conditions,the three kinds of crystalline silicon were prepared into SHJ bottom cells.It was found that the performance of 0.7μm and 1.8μm suved-surface bottom cells was basically the same,and both of them were better than that of the front surface polished crystalline silicon bottom cells.The maximum VOC could reach 0.742V.The maximum size of Jsc(800-1180nm)is 15.24 mA/cm2.2、The study on perovskite thin films of crystal silicon with different surface roughness found that the thickness of perovskite thin films gradually increased with the increase of Ra under the same rotational coating condition,resulting in a gradual decrease in the diffraction peak strength of perovskite phase and PbI2 phase in the thin films.In addition,the average particle size of perovskite on the polished crystalline silicon with the smallest Ra is 555.8nm,the corresponding photoluminescence intensity(PL)spectrum signal intensity is higher,and the perovskite thin films have fewer non-radiative absorption and defects.3、Under the same amorphous silicon film deposition conditions,the influence of the two kinds of bottom cell structure on the bottom cell performance was studied.It was found that the performance of the bottom cell of p-i-n structure(back junction)was better than that of n-i-p structure(front junction),where the maximum VOC was 0.739V and the maximum Jsc(800-1180nm)was 15.0mA/cm2.The i-a-Si:H/c-Si interface passivation optimization is carried out on the basis of the p-i-n bottom cell structure.When the optimal gas flow ratio R(R=H2/SiH4)is 0.4 and the optimal hot wire current is 30A,The minority child lifetime of "i-a-Si:H/c-Si/i-a-Si:H" samples were 3067μs and 2706μs,and iVoc were 0.743V and 0.742V,respectively.In addition,the microstructure factor(R*)and hydrogen content(CH)of i-a-Si:H films are both minimum.The denser the structure of i-a-Si:H films is,the better the interface passivation performance is.