Preparation And Performance Of Antimony Selenide Solar Cells By Close Space Sublimation

Antimony selenide(Sb2Se3)is a promising photovoltaic material with many attractive photovoltaic properties.With appropriate band gap,high absorption coefficient,benign grain boundaries,low toxicity and abundant rare earth elements,the theoretical conversion efficiency can reach 31%.It has become a hot research topic in the field of photovoltaics.The main contents of this topic are as follows:(1)In order to study the growth mechanism and carrier transport behavior of Sb2Se3 thin film,we use the close-spaced sublimation method to prepare Sb2Se3 film.The results show that the microstructure of Sb2Se3 thin film is mainly determined by the competing result of lateral and vertical growth of(Sb4Se6)n ribbons.The ratio of these two growth modes can be significantly adjusted by changing the substrate material.When the Sb2Se3 thin film is deposited onto an indium tin oxide(ITO)substrate,the(Sb4Se6)n ribbons mainly show the lateral growth mode,which leads to poor vertical carrier transport.While the Sb2Se3 thin film deposited onto fluorine-doped tin oxide(FTO)substrate show the preferred orientations of(211),(221)and(301),indicating that the proportion of vertical growth of(Sb4Se6)n ribbons increases.Furthermore,we found that the(Sb4Se6)n ribbons grow perpendicular to the boron-doped zinc oxide(BZO)substrate(pure vertical growth)due to the existence of boron in the substrate.This Sb2Se3 thin film exhibits excellent vertical carrier transport properties and has the potential to yield efficient solar cells.(2)Based on the above experimental results,we prepared a Sb2Se3 light-absorbing layer with the same growth law on the ZnO electron transport layer by regulating the growth conditions,and obtained 3.31%photoelectric conversion efficiency(PCE).Based on SEM results,it can be found that the ZnO electron transport layer has a loose structure,which is detrimental to the performance of the cell and may be one of the reasons for the leakage of the cell.This result was also confirmed in the dark state bias test.Therefore,in order to solve the cell leakage phenomenon,an ultra-thin CdS buffer layer is inserted on the ZnO electron transport layer to fill the gaps and cracks of the ZnO film.The insertion of the buffer layer successfully weakens the non-ohmic contact of the p-n junction and promotes a reasonable energy band alignment,making the collection of carriers more favorable.Therefore,the photoelectric conversion efficiency of PCE=3.57%is obtained,which improves the cell efficiency by 11.56%.(3)We still use the simple CSS method.By fixing the substrate temperature,and then co-evaporating a certain proportion of Sb2Se3 and CuSe mixed powder on the CdS electron transport layer,Sb2Se3 light absorption layers with different Cu doping amounts are successfully prepared.And the effects of different Cu doping concentrations on the microstructure of Sb2Se3 thin film and cell performance are also studied.Through testing,it is found that a certain amount of Cu doping promotes the longitudinal preference of(002)and also reduces the roughness of the film.Additionally,the energy band of the Sb2Se3 film changes due to the Cu doping.This result not only increases the carrier concentration,but also lowers the back contact cell and enhances the collection of carriers,thus obtaining the highest conversion efficiency of PCE=4.11%.However,excessive Cu doping will cause the deterioration of the thin film and increase the defects of the cell,thus degrading the cell performance.The research proves that the doping of the light-absorbing layer has potential applications value for improving Sb2Se3 solar cells.