Interface Charaterization Of Heterojunction Solar Cell And Its Photovoltaic Properties

Solar energy will be a significant component forfuture energy sources due to its unique advantages such as abundant rawmaterial,renewable energy,eco-friendly utilization process.Solar cells,also called photovoltaic(PV)cells,which convert sunlight directly into electricity,have made a great process for last half century.Among all kinds of solar cells,Silicon(Si)-based heterojunction solar cells have been currently under intensive investigation,which benefit from their low cost fabrication processes and achieve high power conversion efficiency(PCE).It is critical for high performance solar cells to select suitable materials to integrate with n-type Si(n-Si)as hole selective contact.Herein,we will focus on two representative hole selective materials MoOx and PEDOT:PSS integrating with Si to investigate their interface and PV performance.The main works can be summarized as follows:Firstly,we presented the investigation of MoOx/n-Si interfaces.We utilize a stepwise in-situ deposition of MoOx to investigate its interaction with Si by X-ray photoelectron spectroscopy(XPS)and ultraviolet photoelectron spectroscopy(UPS)measurements.A strong inversion layer originating from a charge transfer process is quantitatively demonstrated in n-Si surface region upon MoOx contact characterized by XPS,UPS,capacitance-voltage(C-V)measurements.A dopant-free p-n junction is built within n-Si with a high built-in potential(Vbi)of-0.80 V which benefits for acquiring the high open circuit voltage(Voc).These results give a detailed interpretation on carrier transport mechanism of MoOx/n-Si heterocontact.Secondly,we presented the fabrication and properties of MoOx/n-Si heterojunc-tionsolar cells with poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)as transparent conductive electrodes(TCEs).A PCE of 11.8%and a fill factor(FF)of 0.708 were achieved.The conductivity of PEDOT:PSS films increased from 0.5 S/cm to 1800 S/cm with p-hydroxybenzene sulfonic acid(PHSA)treatment while the transmittance was still kept at a high level above 94%.Flexible PEDOT:PSS films were fabricated by using a simple solution-based process compared with the traditional indium tin oxide(ITO)electrodes which limited to brittle characteristic and high-coat sputtering processes.Meanwhile,a flexible device with a PCE of 8.72%was also fabricated.These works suggest a promising approach to fabricate high efficiency,low-cost MoOx/n-Si heterojunction solar cells.Thirdly,we presented the fabrication and properties of PEDOT:PSS/inverted py-ramid nanostructured n-Si heterojunction solar cells with high Voc.We introduced a simple and effective method to improve the contact between nanostructured n-Si and PEDOT:PSS film by inserting(N4,N4'-Di(naphthalen-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine)(VNPB)layer.VNPB is widely used as hole transport layer in photoelectric device which can be thermal crosslinked at 120 ?.A solar cell based inverted pyramid nanostructured n-Si achieved a Voc of 0.640 V,a short circuit current density(Jsc)of 29.1 mA/cm2,a FF of 0.730,a PCE of 13.6%.