Study On Back Contact Optimization Of Antimony Selenide Thin Film Solar Cells

Antimony selenide(Sb₂Se₃)has developed rapidly in recent five years due to its many advantages such as simple composition,excellent optical and electrical properties and environmental protection.However,the low open circuit voltage(V_OC)currently limits the efficiency improvement of Sb₂Se₃ thin film solar cells.A large number of studies have shown that to enhance the P-N junction built in voltage,reduce the recombination of photo-generated carriers,and optimize the transmission of carriers is the key to improve the open circuit voltage and efficiency.On the one hand,the intrinsic p-type carrier concentration of Sb₂Se₃ thin film is very low,and various preparation methods will inevitably lead to complex intrinsic defects which is difficult to restrain in Sb₂Se₃thin film material.On the other hand,the construction of NIP structures is considered to be an effective way to solve the above problems.Among them,back contact optimization is the most important branch of NIP structure construction.Therefore,from the perspective of the back contact optimization of solar cells,studies were carried out in this paper on the basis of rapid thermal evaporation,which is the mainstream in preparing Sb₂Se₃ thin film at present.Different back contact materials were selected to construct superstrate thin film solar cells.The main research contents and results of the studies are as follows:1.The influence of Al₂O₃ thickness on the performance of Sb₂Se₃ thin film and battery was studied.The results show that the thickness of 0.1 nm Al₂O₃ improved Sb₂Se₃ thin film crystalline,carrier concentration and surface roughness,and thus to the greatest degree enhanced external quantum efficiency of thin film solar cells,rectifier features,built-in voltage as well as the open circuit voltage,finally improved the power conversion efficiency.2.Using MoO₃ as the back contact layer to prepare Sb₂Se₃ thin film solar cells,the material properties of the MoO₃ thin film prepared by electron beam evaporation were characterized to reveal its characteristics as the back contact layer and the influence of MoO₃ back contact layer on the photoelectric performance of the device was studied.The results show that the MoO₃ prepared by electron beam evaporation was highly pure and displayed n-type conductivity.Besides,the n-type MoO₃ exhibited a deep valence band edge with a high work function.MoO₃ enhanced the built-in voltage,external quantum efficiency response,and rectification characteristics.Moreover,MoO₃ also inhibited the carrier recombination and enhanced the photo-generated carrier transmission at the Sb₂Se₃ and Au interface.Finally,the device efficiency was improved from 5.12%to 6.33%.3.The magnetron sputtering process was selected to study the influence of different Se sputtering power on the performance of Sb₂Se₃ thin films and devices.The results show that the process of sputtering for Se supplementation enhanced the crystallization of Sb₂Se₃ films.The optical absorption characteristics of the films increased with the increase of Se sputtering power,and the optical band gap decreased with the increase of Se sputtering power.The carrier concentration of the film increased with the increase of Se sputtering power.The mobility decreased with the increase of Se sputtering power.The resistivity of the Sb₂Se₃ thin film was low when the Se sputtering power was 8W and 12W,but was the maximum when the Se sputtering power was 14W.When the Se sputtering power was 12W,the device exhibited the highest external quantum response and the highest power conversion efficiency,up to 6.2%.Compared with the device with Se sputtering power was 14W,the carrier recombination in the back contact region is lower when the Se sputtering power was 12W.The device exhibits the best V_OC and short circuit current density(J_SC)when the width of depletion region is 222nm.