Research On Materials And Devices Of SnSe Thin-film Solar Cells

Due to low preparation cost,excellent photovoltaic performance,and flexible preparation methods,Sn Se thin-film solar cells are known as a new generation of energy devices.However,current Sn Se thin-film solar cells have problems such as immature fabrication process and generally low photoelectric conversion efficiency(<0.8 %).These problems are mainly caused by insufficient research on process technology and photoelectric properties of the Sn Se absorber film.In this paper,the preparation process parameters(substrate temperature,Sn/Se mass ratio,film thickness and evaporation rate)of the Sn Se thin-film solar cell absorber layer prepared by the co-evaporation method were first explored and optimized.Subsequently,microscopic morphology,optical properties,and electrical properties of Sn Se thin films prepared with different process parameters were systematically studied.Moreover,these films were fabricated into solar cells and further studied the effect of substrate temperature,Sn/Se mass ratio,film thickness,and evaporation rate on photoelectric conversion efficiency of these cells.Main work and innovative results are as follows:(1)Grain size,crystallinity,and carrier mobility increase when substrate temperature increases from 400 ? to 460 ?.Besides,dislocation density,recombination rate of carriers at the grain boundary and resistivity decrease with the increase of the substrate temperature from 400 ? to 460 ?.Crystallinity,grain size,and carrier mobility of crystals increase as the Sn/Se mass ratio increases from 1.25 to1.50.Moreover,dislocation density,recombination rate of carriers at the grain boundary and resistivity decrease with Sn/Se mass ratio increases from 1.25 to 1.50.Crystallinity,grain size,and carrier mobility of the crystal decrease as the Sn/Se mass ratio increases from 1.50 to 1.75.Furthermore,dislocation density,carrier recombination rate at the grain boundary and resistivity decrease as Sn/Se mass ratio increases from 1.50 to 1.75.In summary,solar cells prepared under the condition that substrate temperature is 460? and Sn/Se mass ratio is 1.50 has better performance in all samples.Under this condition,both open circuit voltage and short circuit current reach the maximum value in all samples,and finally achieve the best photoelectric conversion efficiency of 0.89 %.(2)Grain size,crystallinity,and carrier mobility increase when film thickness increases from 0.6 ?m to 1.3 ?m.Besides,dislocation density,recombination rate of carriers at the grain boundary decrease when film thickness increases from 0.6 ?m to1.3 ?m.Crystallinity,grain size,and carrier mobility of crystals increase as evaporation rate of Sn increases from 1 ?/s to 2.5 ?/s.In addition,carrier recombination rate and dislocation density at the grain boundary decrease as evaporation rate of Sn increases from 1 ?/s to 2.5 ?/s.Crystallinity,grain size,and carrier mobility of the crystal decrease as evaporation rate of Sn increases from 2.5?/s to 5 ?/s.Besides,dislocation density and recombination rate of carriers at the grain boundaries increase as evaporation rate of Sn increases from 2.5 ?/s to 5 ?/s.All samples have no impurity phases and are pure Sn Se phases.In summary,solar cells prepared under the conditions that the film thickness is 1.3 ?m and the evaporation rate of Sn is 2.5 ?/s shows best performance in all samples,with the highest photoelectric conversion efficiency of 1.02 %.