高效硫硒化锑薄膜太阳电池中的渐变能隙结构

Bandgap grading of Sb_(2)(S,Se)_(3) for high-efficiency thin-film solar cells

硫硒化锑(Sb_(2)(S,Se)_(3))薄膜太阳电池因其原材料丰富、制备方法简单、性能稳定等优势近年来得到了快速发展.本文基于Sb_(2)(S,Se)_(3)吸光层能隙可调的特点,应用wx-AMPS软件对具有渐变能隙Sb_(2)(S,Se)_(3)太阳电池进行建模仿真和结构设计,并与50%Se含量的恒定能隙Sb_(2)(S,Se)_(3)太阳电池进行了对比分析.结果显示,递减能隙结构所形成的附加电场能够促进空穴的输运,抑制载流子的复合,相比与恒定能隙Sb_(2)(S,Se)_(3)太阳电池可以得到更高的短路电流密度和填充因子,使光电转换效率由12.03%提升至14.42%.此外,递减能隙结构通过抑制载流子的复合,有效地缓解Sb_(2)(S,Se)_(3)太阳电池因厚度厚或者缺陷态高所引起的性能下降.在厚度为1.5μm,缺陷态密度在1016 cm^(–3)时.采用递减能隙Sb_(2)(S,Se)_(3)太阳电池的效率比恒定能隙Sb_(2)(S,Se)_(3)太阳电池高6.34%.研究结果表明通过吸光层的能隙结构设计能够发挥Sb_(2)(S,Se)_(3)等多元合金或化合物的能隙可调的优势,是提高太阳电池器件性能的有效技术路线之一.

Sb_(2)(S,Se)_(3) thin film solar cells have been developed rapidly in recent years due to their abundant raw materials,simple preparation method,stable performance,etc.In this study,based on the characteristic of tunable band gap of Sb_(2)(S,Se)_(3) light absorption layer,wx-AMPS software is used to simulate and design the Sb_(2)(S,Se)_(3) solar cell with narrowing band gap structure,and compared with the Sb_(2)(S,Se)_(3) solar cell with constant band gap(50%selenium content).The results show that the additional electric field formed by the narrowing band gap can promote the holes’transport and inhibit the carrier’s recombination.Compared with the constant band gap structure,the narrowing band gap structure can increase the short-circuit current density of Sb_(2)(S,Se)_(3) solar cells from 19.34 to 22.94 mA·cm^(–2),the filling factor from 64.34%to 77.04%,and the photoelectric conversion efficiency from 12.03%to 14.42%.Then,the effect of electron mobility on the performance of Sb_(2)(S,Se)_(3) solar cells with narrowing band gap is studied.It is found that when the hole mobility is 0.1 cm^(2)·V^(–1)·s^(-1),the advantage of narrowing band gap can gradually appear after the electron mobility is higher than 0.25 cm^(2)·V^(–1)·s^(-1).The performance of Sb_(2)(S,Se)_(3) solar cell is enhanced with the electron mobility further increasing.However,when the electron mobility is higher than 5 cm^(2)·V^(–1)·s^(-1),the device performance is saturated.Moreover,we demonstrate that the degradation caused by thick or high defect state of Sb_(2)(S,Se)_(3) solar cell can be effectively alleviated by applying the narrowing band gap due to the suppression of the carrier recombination.When the thickness is 1.5μm and the defect density is 1016 cm^(–3),the photoelectric conversion efficiency of Sb_(2)(S,Se)_(3) solar cell with narrowing band gap is 6.34%higher than that of the constant bandgap.Our results demonstrate that the band gap engineering of the light absorption layer is one of the effective technical routes to optimizing the performance of Sb_(2)(S,Se)_(3) solar cells.Since the photo-absorption material such as amorphous/microcrystalline silicon germanium,Copper indium gallium selenide and perovskite have the characteristic of tunable band gap.The design of the gradient band gap structure can also be applied to the optimization of the above alloy or compound solar cells.