新型硒化锑薄膜太阳电池背接触优化

Back contact optimization for Sb_(2)Se_(3) solar cells

硒化锑(Sb_(2)Se_(3))具有低毒、原材料丰富和光电性能优异等优点,被认为是最具有发展潜力的薄膜太阳电池光吸收层材料之一.但目前Sb_(2)Se_(3)薄膜太阳电池光电转换效率与碲化镉、铜铟镓硒和钙钛矿等太阳电池相比仍存在较大差距.限制Sb_(2)Se_(3)薄膜太阳电池光电转换效率进一步提升的关键因素之一是,太阳电池结构中Mo背电极和Sb_(2)Se_(3)薄膜构建的背接触界面处容易形成较高的势垒,降低载流子的抽取效率.本工作则对Mo背电极进行热处理生成缓冲层MoO_(2)薄膜,发现缓冲层MoO_(2)的引入,可有效地促进Sb_(2)Se_(3)薄膜的择优取向生长,同时实现太阳电池Mo/MoO_(2)/Sb_(2)Se_(3)背接触势垒降低,相应的填充因子、开路电压和短路电流密度均获得显著提高,构建的太阳电池光电转换效率从5.04%提升至7.05%.

Antimony selenide(Sb_(2)Se_(3))has advantages of low-toxicity,abundant and excellent photoelectric properties.It is widely considered as one of the most promising light-harvesting materials for thin-film solar cells.However,the power conversion efficiency of the Sb_(2)Se_(3)thin-film solar cell is still far inferior to that of cadmium telluride,copper indium gallium selenium and perovskite solar cells.As is well known,the Sb_(2)Se_(3)solar cell performance is closely related to the light absorber layer(crystallinity,composition,bulk defect density,etc.),PN heterojunction quality(charge carrier concertation,energy band alignment,interface defect density,etc.)and back-contact barrier formation,which determines the process of carrier generation,excitation,relaxation,transfer and recombination.The low fill factor is one of the core problems that limit further efficiency improvement of Sb_(2)Se_(3)solar cells,which can be attributed to the high potential barrier at the back contact between the Mo electrode and Sb_(2)Se_(3) absorption layer.In this work,a heat treatment is applied to the Mo electrode to generate a MoO_(2)buffer layer.It can be found that this buffer layer can inhibit MoSe2film growth,exhibiting better Ohmic contact with Sb_(2)Se_(3),and reducing the back contact barrier of the solar cell.The Sb_(2)Se_(3)thin film is prepared by an effective combination reaction involving sputtered and selenized Sb precursor.After introducing the MoO_(2)buffer layer,it can also promote the formation of(hk1)(including(211),(221),(002),etc.)preferentially oriented Sb_(2)Se_(3)thin films with average grain size over 1μm.And the ratio of Sb to Se is optimized from 0.57 to 0.62,approaching to the stoichiometric ratio of Sb_(2)Se_(3)thin film and inhibiting the formation of Vseand SbSedefects.Finally,it enhances the open-circuit voltage(VOC)of solar cells from 0.473 to0.502 V,the short-circuit current density(JSC)from 22.71 to 24.98 mA/cm~2,and the fill factor(FF)from46.90%to 56.18%,thereby increasing the power conversion efficiency(PCE)from 5.04%to 7.05%.This work proposes a facile strategy for interfacial treatment and elucidates the related carrier transport enhancement mechanism,thus paving a bright avenue to breaking through the efficiency bottleneck of Sb_(2)Se_(3)thin film solar cells.