Effect Of Cationic Doping On Properties Of M₂ZnSn?S,Se?₄?M=Cu,Ag? Absorption Layer And Performance Of Relevant Photovoltaic Devices

In recent years,owing to plentiful component elements,band gap adjustable?1.0-1.5 eV?and high absorption coefficient(10⁴ cm^-1),Cu₂ZnSn?S,Se?₄?CZTSSe?with kesterite structure has developed rapidly.The optimal photoelectric conversion determinan?PCE?of CZTSSe film solar cell has been achieved was 12.6%,which is far further behind the theoretical expectation?31%?.The factors that the PCE of the CZTSSe solar cell can not be improved include the following:there existence of a large number of CuZn defects bring about the serious open circuit voltage(V_OC)deficiency.Secondly,the crystal quality of CZTSSe absorption layer was discussed.These determinant limit the further improvement of the efficiency.Some studies indicate that replace part of copper?Cu?with silver?Ag?in CZTSSe can effectively inhibit the formation of Cu _Zn defect,eliminate Fermi level pinning and improve the open circuit voltage.However,the optimum selenization temperature can be reduced by Ag-alloyed CZTSSe,which is a most critical parameter to control the electrical and optical properties of CZTSSe films.Therefore,finding the superlative selenization temperature is crucial for the further development of CAZTSSe based film solar cells.Ag₂ZnSn?S,Se?₄?AZTSSe?are n-type conductive materials.AZTSSe has a suitable band gap between 1.3-1.4 eV and an absorption coefficient higher than 10⁴ cm^-1.Moreover,the band alignment between AZTSSe and CdS is ideal and is considered to be a promising absorbent materia.However,research findings that AZTSSe has low carrier concentration,high resistivity and poor crystal quality,which slowed down the application and development of AZTSSe films.For the former problem,the effect of Ag alloying and selenization temperature on performance of the CZTS-based solar cell were systematically studied.To solve the latter problem,we introduced different content of Sb atoms into Ag₂ZnSn?S,Se?₄ films,hoping to improve the performance of AZTSSe films.The achievements of scientific research are as follows:1.In this paper,the single-phase of(Cu_1-xAg_x)₂ZnSn?S,Se?₄ films was successfully prepared by sol-gel method,and the influence of Ag doping CZTSSe films on electrical properties and device performance was investigated.The composition and electrical properties of Ag-doped CZTSSe were tested.It was found that the Ag was introduced to CZTSSe could reduce the carrier concentration,increase the space charge area,enhance the carrier collection,and improve the external quantum efficiency?EQE?in the wide spectral range from 600 nm to 1100 nm.Moreover,after silver doping,the PCE of CAZTSSe solar cell increased from 4.48%to 5.94%,mainly because the doping of Ag⁺changed the optical band gap,series resistance?R_S?and shunt resistance(R_Sh)of CZTSSe,thus increasing the open circuit voltage(V_OC)and fill factor?FF?of the device.2.For improving PCE of the CAZTSSe solar cell,we optimized crystalline quality of the CAZTSSe flms by adjusting selenization temperatures.CAZTSSe films and corresponding solar cells were prepared by adjusting the selenization temperature.The temperature range is 550-510?.The influence of selenization temperature on the crystallization quality,electrical properties,the thickness of MoSe₂ and performance of CAZTSSe films was systematically analyzed.It is found that the PCE of solar cells increases firstly and then decreases with the decrease of selenization temperature.At530?,the PCE of CAZTSSe solar cell was prepared with PCE of 7.91%.Through data analysis,it is not difficult to find that the change of efficiency is mainly caused by the change of series resistance?R_S?,diode ideality?A?and reverse current?J₀?,while the change of R_S is not affected by the thickness of MoSe₂.The variation of these parameters is mainly determined by crystal quality and grain size of CAZTSSe films,and the interface structure of CAZTSSe/CdS and CAZTSSe/Mo.3.The Sb atom was incorporated into Ag₂ZnSn?S,Se?₄ to improve the crystalline quality and electrical properties of films.Sb-doped Ag₂ZnSn?S,Se?₄ nanocrystalline films were successfully prepared by metal salt/thiourea method combined with selenization annealing technology.The effect of Sb impurity on the morphology and electrical properties of AZTSSe films was studied.Research findings that Sb doping can effectively improve the morphology and improve the crystalline quality of the films.However,it has influence on the improvement of carrier concentration.Further research is needed to change AZTSSe carrier concentration or realize transformation of AZTSSe.