Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池数值模拟

银锌锡硒(Ag2ZnSnSe4)是一种禁带宽度为1.4 eV的n型半导体材料.本文提出一种由n型Ag2ZnSnSe4与石墨烯(Graphene)组成的Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池,并借助wxAMPS软件对电池的物理机理和性能影响因素进行模拟研究.模拟结果表明,高功函数的石墨烯与n型Ag2ZnSnSe4半导体接触时,Ag2ZnSnSe4吸收层的前端能带向上弯曲,在n型Ag2ZnSnSe4吸收层表面诱导形成p型Ag2ZnSnSe4反型层,p型Ag2ZnSnSe4和n型Ag2ZnSnSe4组成p-n同质结.模拟发现石墨烯和背接触的功函数会影响载流子的分离、输运和收集,严重影响器件性能,石墨烯功函数达到5.5 eV,背接触功函数不高于4.4 eV,都有利于提高器件性能.Ag2ZnSnSe4吸收层的掺杂浓度主要影响器件的短路电流,而Ag2ZnSnSe4吸收层的体内缺陷对器件整体性能产生影响.在石墨烯和背接触功函数分别为5.5和3.8 eV,Ag2ZnSnSe4吸收层的掺杂浓度和缺陷密度分别为1016和1014 cm–3时,Graphene/Ag2ZnSnSe4诱导p-n结薄膜太阳电池能够取得高达23.42%的效率.这些模拟结果为设计新型高效低成本太阳电池提供了思路和物理阐释.

Numerical simulation of graphene/Ag2ZnSnSe4 induced p-n junction solar cell

Ag2ZnSnSe4 is an n-type semiconductor with a suitable bandgap of 1.4 eV.In the present study,a graphene/Ag2ZnSnSe4 induced p-n junction thin film solar cell is proposed and the physical mechanism and performance influencing factors of the solar cell are simulated and analyzed by using the wxAMPS software.The simulation results show that when a high work function graphene contacts an n-type Ag2ZnSnSe4 semiconductor,the energy band of the Ag2ZnSnSe4 absorber layer bends upward,meanwhile a p-type Ag2ZnSnSe4 inversion layer is induced on the surface of n-type Ag2ZnSnSe4,therefore the p-type Ag2ZnSnSe4 and n-type Ag2ZnSnSe4 form an induced p-n homojunction.It is found that the work function of graphene and back contact significantly influence the photogenerated carrier separation,transportation and collection.The graphene work function should be 5.5 eV and the work function of back contact should not be greater than 4.4 eV,which is beneficial to the improving of the device performance.The doping concentration of Ag2ZnSnSe4 absorber mainly affects the short-circuit current of the device,however,the defect density of Ag2ZnSnSe4 absorber affects the whole device performance.When the work function of graphene and back contact are 5.5 eV and 3.8 eV,the doping concentration and defect density of Ag2ZnSnSe4 absorber are 1016 cm–3 and 1014 cm–33,respectively,the conversion efficiency of the graphene/Ag2ZnSnSe4 induced p-n junction thin film solar cell can reach 23.42%.These simulation results provide the idea and physical explanation for designing a novel type of solar cell with high efficiency and low cost.