Structure And Interface Engineering For Organic/Silicon Heterojuction Solar Cells

With the rise of the energy revolution,environmental friendly renewable energy attracts wide interests.Since the 1980s,solar cells have been a hot research topic with the advantages of inexhaustible,efficient.stable,clean and safe.Hybrid solar cells combine organic and inorganic materials with the aim of utilising the high stability and carrier mobility of inorganic materials,as well as obtaining low cost,simple and flexible preparation of organic materials.Silicon(Si)/organic heterojunction solar cells based on poly(3.4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)and n-type Si have attracted wide interests because they promise cost-effectiveness and high-efficiency.The Si/PEDOT:PSS heterojunction formed at room temperature or low temperature simplifies the fabrication process,reduces the cost,and avoids the negative effects of high temperature induced problem.However,while hybrid solar cells have the potential to achieve high power conversion efficiencies(PCE),and currentl power conversion efficiencies have been reported over 16%.Further improvement still need to target possible future application.It is important to improve the efficiency of solar cell.In this paper,we have investigated the stability of the cells,particularly the organic part.The design of the electrode is crucial to avoid any optical loss and improve carrier collection eff iciency.Moreover,in oder to improve the device performance,Si morphology and rear contact is also investigated.Followings are the main content of this work:1.We have demonstrated a tunable and vivid color generation based on the non-lithographic patterning Si nanoholes.The nonlithographic metal assistant Si etching process is applied to fabricate Si nanoholes,which is low cost,simple fabrication and high throughput.Importantly,the color generation from nonlithographic patterning Si nanohole is angle independed.The relative reflected spectrum depended the electric and magnetic resonances can be easily tuned with the depth of Si nanoholes by the etching time.Finally,we applied this structure in the field of image display and sensing application.2.We have investigated a new type of infrared photo-doping to form the back field to improve the back electrode contact of silicon/PEDOT:PSS hybrid solar cells.A black phosphorus(BP):zinc oxide(ZnO)composite layer was inserted between Si and aluminum(Al)to improve their contact.Once the BP harvests photons with energies below 1.1 eV,the ZnO carrier concentration increases dramatically due to charge injection.This photo-induced doping results in a high carrier concentration in the ZnO film,mimicking the modulated doping technique used in semiconductor heterojunctions.We show that photo-induced carriers dramatically increase the conductivities of the BP-modified ZnO films,thus reducing the contact resistance between Si and Al.A photovoltaic power conversion efficiency of 15.2%is achieved in organic-Si heterojunction solar cells that use a ZnO:BP layer.3.We have developed a strategy to balance PEDOT:PSS conductivity and grid optical transmittance via a buried molybdenum oxide/silver grid electrode.The grid electrode coverage ratio is optimized from 12%to 7.8%.to reduce its light shading effect.The buried electrode dramatically reduces the device series resistance,which leads to a higher fill factor(FF).With the optimized buried electrode,a record FF of 80%is achieved for flat Si/PEDOT:PSS heterojunction devices.With further enhancement adhesion between the PEDOT:PSS film and Si substrate by a chemical cross-linkable silance,a power conversion efficiency of 16.3%for organic/textured Si heterojunction devices is achieved.4.We have investigated the electrical properties of PEDOT:PSS film during annealing process.The stability of PEDOT:PSS film was investigated.It showed that the moisture in air displayed negative influence on electrical properties of PEDOT:PSS film.In order to improve the stability of Si/PEDOT:PSS hybrid solar cells,we applied hydrophobic chemical component as a protective layer,and found that the protective layer can not only effectively improve the stability,but also reduce the reflection of the solar cell.The PCE of protected device only decay less than 10%,while the reference shows an 80% attenuation.