Preparation And Performance Study Of Lead Sulfide Thin Film Materials

Quantum dots(QDs)with special properties have received widespread attention from researchers all over the world in recent years.And QDs are becoming one of the preferred materials for assembling efficient and practial devices.Among them,lead sulfide(Pb S)has an exciton Bohr radius as high as 18 nm due to its bulk bandgap as low as 0.41 e V.It is easier to obtain QDs particles with quantum effects by adjusting the reaction parameters,so Pb S has become a research hotspot at present.However,the low mobility caused by the localization effect greatly constrains the transport and collection of charges.Therefore,Pb S QDs often appear in pairs with graphene with high carrier mobility.At present,the focus of research on this composite system is to improve the responsivity of applied devices and explore the factors that affect the responsivity.However,there are few studies on the effect of graphene on the assembly growth of Pb S QDs.Secondly,although there are many methods to synthesize Pb S QDs,the mainstream technology is still the heat injection method.However,the higher decomposition temperature of the precursor and the harsh synthesis environment greatly increase the production cost.Therefore,it is of great value to propose a relatively mild and efficient preparation process.With the above-mentioned problems as the core,this thesis has conducted the following researches:1.Firstly,thin film samples were synthesized by chemical liquid phase method with thiourea(SC(NH₂)₂)as precursor.Pb S thin films with high crystalline quality and preferred orientation were obtained.The band gap value was about 0.645 e V.The grain size of the sample was equal to 40.88 nm.By adjusting the concentration of SC(NH₂)₂,the grain size was successfully reduced to 29.69 nm,approaching the critical scale of 18nm.Secondly,QDs thin films with the band gap of 1.099 e V were successfully synthesized by adopting a solution method with butylamine as the core.It was proved that the deposition time was the key parameter to regulate the particle size.The decrease of deposition time resulted in a reduction in particle size down to 20 nm.2.PbS sol was successfully synthesized.And at room temperature the obtained samples had better stability.The grain size was concentrated at 5-6 nm,which was significantly smaller than the exciton Bohr radius of 18 nm.Secondly,the Pb S QDs/graphene heterostructure was constructed by the homogenization technology.And the reaction parameters that affect the synthesis of the sample,such as the time of heat treatment,the ratio of Pb/S,etc.,were studied.The results showed that the heat treatment was a key step in the preparation of the sol.At the same time,the increase of Pb/S ratio resulted in a decrease in particle size.3.Exploring the application of PbS QDs/graphene heterostructures.Firstly,the structure was applied to a detection device,and the photosensitive characteristics were measured.The calculated resistance change rate of the sample with or without light was about 40.0%.It showed that the structure could respond effectively to the change of external incident light.Then a prototype of the photovoltaic structure was constructed and its performance parameters were measured.The open-circuit voltage(V_oc),the short-circuit current density(J_sc),and the fill factor(FF)were equal to 0.39 V,2.38(?A·(cm)^-2),and 35.94%,respectively.It was proved that the structure could generate photovoltaic phenomenon.