Precious Metal Nanostructures Improve The Performance Of Thin Film Silicon Solar Cells

The insufficient active layer thickness of thin film a-Si solar cell leads to weak absorption for visible light,especially the red light.The infrared photons' energy can be rarely utilized owing to the broad bandgap of a-Si(1.7eV).The combination of two or more infrared photons' energy into one visible photon's energy through upconversion luminescent materials seems to be a promising way to reduce energy loss in infrared range.However,the upconversion luminescence quantum yield is too small to apply it into TFSC under natural illumination.The surface plasmonic resonance effect of noble metal structure coupling with incident beam of specific frequency results in two main consequences.One one hand,the electric field intensity closed to the metal surface,which named as near field,is much larger than the initial incident light's electrical field intensity.The absorption of a-Si for visible light could be enhanced when it placed in the vicinity of noble metal structure.On the other hand,the upconversion process can be modulated when luminous-center placed nearby the noble metal structure.Thus,the upconversion luminescence intensity obtains a considerable enhancement under natural light illumination.In this framework,we designed an array of subwavelengh silver spheres and placed it onto the top surface of TFSC.Hence the absorption of active layer for visible energy in AM1.5G could be further improved.Additionally,a complex substrate consists of gold nanorods and upconversion materials,was put at the bottom of TFSC.It can produce usable visible radiation under natural infrared excitation.The infrared excitation was the transmission of AM1.5G at the rear side of TFSC.Our explorations include the following items.(1)An structure parameter optimization of the subwavelenth silver sphere array was performed to maintain a favorable light trapping result.(2)The improvement about electrical properties of TFSC with surface subwavelength silver sphere array was investigated.An analysis of performance enhancement on the basis of light harvesting and carrier separation was performed.(3)The interaction between gold nanorod and luminous center was investigated.We drew a conclusion about conditions for enhancing luminescence.(4)We designed the substrate structure of gold nanorods and upconverter.The performance enhancement of TFSC with the disigned substrate under AM1.5G illumination was explored.We investigated the feasibility of upconverter applying to TFSC under natural irradation.