New Electron-Selective Contact Materials For Organic-Inorganic Hybrid Solar Cells

The solar cells include three functional materials such as the absorber,carrier-selective contact layers,and interface passivation layers.High-quality interface passivation and highly effective carrier-selective contact are basic prerequisites for high-efficiency crystalline Si solar cells.However,high-efficacy solar cells always employ two or more materials to achieve interface passivation and carrier transport.Passivating contact incorporate thin films within a stack contact structure that simultaneously suppress recombination and promote charge-carrier selectively transport in devices.Thus far,the most successful and empirically realizable example of passivating contact is the heterocontacts with asymmetric work functions on top of a thin passivating layer applied to the c-Si surface,such as so-called such as dopant-free asymmetric heterocontact?DASH?solar cells and organic-inorganic hybrid solar cells.Instead of p-n junction,the passivating contact is based on the difference of work function between two materials to tailor the energy lineup of heterojuncton,leading to the simple device structure and fabrication process.In this thesis,several new electron-selective contact materials were investigated for organic-inorganic hybrid solar cells,including three sections as follows.???The Rubrene:DMSO thin layer is introduced onto the rear side of the organic/inorganic hybrid solar cells as an efficient electron-selective contact,leading to significant improvement in the device performances.A Rubrene:DMSO composite film is fabricated by a spin-coating method.It is found that the Rubrene:DMSO thin film has a low work function of 3.84 eV,being lower than the electron affinity of the n-Si?4.05 eV?,which could tailor energy band structures.Since the Rubrene:DMSO thin layer is inserted between Si and Ag,the rear energy band achieves downward band bending,promoting the effective transport of electrons and suppressing the recombination of the holes.The optimal hybrid solar cell exhibits an average PCE of 11.9%and a maximum PCE of 12.1%.Moreover,this thesis presents the observation of an abnormal light-induced enhancement?LIE?effect in photovoltaic performance in organic/inorganic hybrid solar cells.With the light soaking,open circuit voltage(V_oc)shows the increase of relatively 8.9%and PCE shows the increase of relatively 16%.The passivating-contact interface is found to include light-induced-forming of the PSS/?SiOx?/Si species,being responsible for the LIE of the hybrid solar cells.The reduced density of interface defect states under light soaking leads to the improvement of the photovoltaic performances.???A hafnium?Hf?thin film is introduced for the first time as the rear metallization scheme on the rear side of organic/inorganic hybrid solar cells to achieve higher PCE.Hf thin films are uniformly deposited at room temperature by sputtering technology,showing its advantages of stable electrical ability.The insertion of Hf thin film reduced interfacial carrier recombination and contact resistance loss,leading to a significant improvement in V_oc and fill factor?FF?of the hybrid solar cells.Eventually,a high PCE of 9.73%is obtained.This efficacy could be attributed to low work function of Hf thin film to ensure the highly transparent to electrons at the rear side of the hybrid solar cell.This study indicates that Hf film can be used as an effective contact layer for engineering back surface of organic-inorganic hybrid solar cells.???n-type organic-inorganic hybrid solar cells have been extensively attracted because of well-known hole-selective PEDOT contact,however,little publication was done for p-type organic-inorganic hybrid solar cell probably due to lack of effective electron-selective contact materials with p-type Si.Here,a p-type organic-inorganic hybrid solar cell is presented through using a C₆₀0 electron-selective contact to p-type Si wafer.The C₆₀0 thin film was fabricated using spin-coating.The device structure as well as the effect of the concentration of C₆₀ solution on device performances were investigated.Devices subjected to a 3-day aging treatment in N₂ and post-annealing at 140?for 15 min yielded the best performance with the PCE of 7.42%.This study offers a viable and explorative way for next p-type organic-inorganic hybrid solar cells.