Investigation On Polymer/Nanocrystal Hybrid Solar Cells With ZnO Electron Transport Layer And Their Properties

With the increasing of global energy consumption,environmental degradation and resource depletion,people has realized the importance of developing clean and sustainable solar energy.Aqueous-processed polymer and nanocrystals（NCs）hybrid solar cells（HSCs）have attracted wide attention of researchers due to the flexibility,portability of polymers and high extinction coefficient,adjustable band gap of NCs.In recent years,people have made advances in manipulating the defects in active material and optimizing device architecture,etc.However,it has been long a challenge to improve carrier transport,enhance extraction ability and control the width of the depletion region.To solve the above problems,this thesis mainly carried out the following two aspects of work:（1）CdTe/PPV single-side bulk heterojunction（BHJ）HSCs with ZnO as electron transport layer（ETL）.The device structure was ITO/ZnO/CdTe/CdTe:PPV/MoO₃/Au.By studying the photophysical properties of sol-gel ZnO,ZnO possessed the characteristics of high transmittance and high conductivity than that of sol-gel TiO₂ used in aqueous-processed method,which enhanced the absorption of light,increased short-circuit current(J_sc),improved carriers transport ability,extraction efficiency and fill factor（FF）.In addition,a large energy difference between ZnO and CdTe accelerated the injection of electrons from CdTe to ZnO.Compared with the TiO₂ ETL,the ZnO ETL had a stronger ability to extract electrons,which accelerated the separation of carriers in the CdTe phase,leading to high FF.Finally,power conversion efficiency（PCE）of 4.68%was obtained.The PV performance of the device with ZnO ETL was improved by 11.4%,compared to that of TiO₂ ETL.（2）ZnO/CdTe and CdTe/PPV double-side BHJ HSCs by ZnO as ETL.To widen the width of depletion region and prolong carrier lifetime,on the basis of（1）,a layer of ZnO:CdTe film was successfully applied to double-side BHJ solar cells.The device structure was ITO/ZnO/ZnO:CdTe/CdTe/CdTe:PPV/MoO₃/Au.The optimum PCE of 6.51%was obtained by adjusting the thickness and morphology of ZnO:CdTe film.The in-depth studies showed that thick ZnO:CdTe film increased the optical absorption,enhanced carrier extraction ability,extended the width of depletion region and prolonged carrier lifetime,increasing J_sc and FF,compared to TiO₂:CdTe film.The highest J_sc of 19.5 mA cm^-2 and the widest depletion region width of 177 nm were obtained based on aqueous-processed HSCs.