Research On The Preparation And Performance Optimization Of High-efficiency Crystalline Silicon Heterojunction And Perovskite Solar Cells

Silicon heterojunction?SHJ?solar cells and perovskite solar cells as well as their tendem cells are outstanding in the first generation and the third generation solar cells due to their advantages of high PCE and low cost which arouse wide concern and research interests in recent years.This thesis is based on these two kinds of solar cells,which focus on their light absorption and carrier collection by lowing the parasite absorption and reducing the carrier recombination to improve the light and power conversion efficency.The first section of research is aim to a-Si/c-Si SHJ solar cell which contains the key factors such as enhancing light capture,increasing the minority carrier lifetime of passivated silicon wafer,lowering the parasitic absorption loss that can lead to the higher PCE.The second section of research is aim to PEDOT:PSS/c-Si heterojunction solar cell.The high PCE of PEDOT:PSS/c-Si SHJ solar cell in normal structure is just 13%at present.We can improve the PCE if we induce the surface and field passivation technology into solar cells and use inverted structure in the meantime.The third section of research is aim to MAPbI₃ perovskite solar cell.The defect could be in both perovskite absorbance layer and each interface in solar cell that could result in carrier recombination loss.We used graphdiyne QDs to modify the surface and inside of solar cell that can lower the trap density,enhance the efficiency of carrier use and boost the PCE.Then we applied all inorganic CsPbX₃?X=Cl,Br,I?perovskite QDs materials into Perovskite solar cell in order to strengthen the stability and PCE.This work lays the foundation for the development of high performance crystalline silicon SHJ solar cell,high performance and stable Perovskite solar cell and their tendem solar cells.Our main research findings as following:I.After the crystalline silicon?c-Si?wafer surfaces were textured as random pyramid structure,intrinsic and doped amorphous silicon?i/n/p a-Si?films,as well as ITO films,were deposited by plasma enhanced chemical vapor deposition?PECVD?process.Microwave transient photoconductive decay?TrPCD?and Fourier Transform Infrared Spectroscopy?FTIR?technologies were used to investigate the influences of i-a-Si film qualities on the c-Si surface passivation.By optimizing such PECVD parameters as temperature,power,pressure,and gas flow ratio,the minority carrier lifetime of passivated c-Si reaches to 3 ms and carrier recombination velocity on a-Si/c-Si interface lowered to 2 cm/s.Transmission spectroscopy and the Hall magnetometery were applied to measure the transmittance of p-a-Si and the carrier concentration and mobiliy of ITO,respectively,which affects the performances of SHJ solar cells.Using p-a-SiC as emitter layer and by optimizing the ITO film deposition process,which effectively reduces parasite absorption in solar cells and increases the EQE near the UV and near infrared wavelengths,with integrated Jsc over 40.5 mA/cm.The efficiency of the fabricated SHJ solar cells by comprehensive optimization reached to 21.28%.II.The influences of surface,field passivation and window layer parasite absorption on the performances of PEDOT:PSS/c-Si heterojunction solar cell?HSC?.The PEDOT:PSS film shows significant parasite absorption in 600-1100 nm region.Combining with surface and field passivation technology in SHJ solar cells and depositing the PEDOT:PSS on the rear side of the c-Si wafer,we developed an inverted structured HSC with much higher solar cell response in 600-1100 nm spectrum.Jsc has been significantly increased from 29.7 mA/cm² to 36.2 mA/cm² and the power conversion efficiency?PCE?of the inverted HSC is improved to as high as 16.1%.III.Novel ?-graphdiyne quantum dots?GD QDs?is used in perovskite solar cells as a surface modifier or dopant to TiO₂,CH₃NH₃PbI₃,and Spiro-OMeTAD to realize multiple advantageous effects,in hoping that it would form a more effective carrier transport channel for boosted solar cell performance.Firstly,the presence of GD QDs on TiO₂ surface increases perovskite grain size for higher current density and fill factor.Secondly,the GD QDs at each interface reduces the conduction band offset,passivates the surface for suppressed carrier recombination to attain higher open-circuit voltage.Thirdly,it improves hydrophobicity and eliminates pinholes in the Spiro-OMeTAD film for enhanced solar cell stability.Finally,doped with GD QDs,CH₃NH₃PbI₃ film with larger crystals was formed,significantly reducing carrier the transmission resistance and improving carrier lifetime.As a result,the optimized device shows>15%enhancement in power conversion efficiency?from 17.17%to 19.89%?comparing to the reference device.IV.The all-inorganic CsPbCl₃:Mn,CsPbBr₃ and CsPbI₃ perovskite quantum dots?QDs?were prepared by hot-injection method,and their applications in solar cells were also studied.First,CsPbCl₃:Mn based quantum dots?QDs?are designedzed and applied onto the front side of the perovskite solar cells as the energy-down-shift?EDS?layer,improving the efficiency and stability for photovoltaic devices.Second,uniform,compact,larger grain size and few defect dual-phase CsPbBr₃-CsPb₂Br₅ composite film was obtained from CsPbBr₃ quantum dots via optimizing by thiocyanate ethyl acetate?EA?solution in all-ambient condition.The fabricated solar cells show the record champion efficiency of 6.81%,as well as long-term stability.Finally,the stability of a-CsPbI₃ QD film after stored in ambient condition?30%RH and 25 ??and post-annealed at different temperature was studied.The efficiency of solar cells based on a-CsPbI₃ QD film has been improved to 5.87%,the work is ongoing.