Theoretical analysis and modelling of ZnO or Si heterojunction solar cell

Abstract

There is a reasonably high gap between production and consumption of electrical energy due to highly power consuming electronics gadgets, industrial and domestic applications. In this regard solar cell is a ray of hope to fulfil the blank. Study of solar cell based on heterojunction between ZnO and crystalline silicon is the major work in this thesis. ZnO is considered as one of the key ingredient in solar cell due to its rich property in both optical and electrical field. Onset of this study is investigation of effect of small AC signal on heterojunction Al=µcand#8722;ZnO=cand#8722;Si=µcand#8722;Si1and#8722;xOx: H=Ag solar cell performance using AFORS-HET V2.5 simulator. In addition effects of interface defect state density located at heterojunction and temperature on capacitance and conductance are studied as well. The study reveals that increase in signal frequency causes fall in junction potential. Afterwards, in order to provide a passivation layer to ZnO a thin layer of MgZnO is used. 2:257% and 5:32mAcmand#8722;2 change in efficiency and short circuit current density is observed while comparing the devices with and without MgZnO layer under AM1:5 illuminations. In order to study the effect of temperature on minority carrier lifetime and rear surface recombination velocity, a heterojunction between amorphous ZnO and crystalline Si model is calibrated with a similar practical device that is existing. Such study reveals that voltage at open circuit and current at short circuit of the model decreases under the effect of high temperature. Variation of surface recombination velocity at interface between base and back surface field with rise in temperature is observed as well. In addition to the above advantages in our proposed model, a thin intrinsic layer is incorporated in the device to improve the performance. As a result, Al=aand#8722;ZnO=iand#8722;ZnO=cand#8722;Si=µcand#8722;Si1and#8722;xOx: H=Ag heterostructure is formed. Due to the insertion of intrinsic layer the fill factor and conversion efficiency of the device increased to around 75:71% and 21:23% respectively.