EAGER: TDM solar cells: High Efficiency Perovskites and CuInSe (CIS) Tandem Solar cells

摘要：非技术性：硅是世界上使用的主导光伏技术。这些太阳能电池被组装在一起生产太阳能电池板。它们占据了太阳能电池板市场90%以上的份额。硅晶体太阳能电池的最大光伏太阳能转换效率约为25%，在过去的10年里，这一转换效率并没有太大的提高。另一方面，串联太阳能电池利用具有不同带隙的两种不同材料的堆叠，可以大幅提高太阳能电池的能效，这将导致产生相同能量所需的太阳能电池板数量减少。该项目基于一种太阳能电池，该电池由一层薄薄的钙钛矿和一层薄薄的铜铟二硒化物(CIS)整体堆叠在一起，总厚度为2.5-3微米，预计能量转换效率接近30%。与晶硅太阳能电池相比，这些太阳能电池将允许能量转换效率的巨大飞跃。它们还将允许为许多低成本应用实现灵活的太阳能电池。串联太阳能电池使用由三种元素组成的硫化物材料：铜、铟和硒，但不使用镓，这是单结CIGS太阳能电池的典型做法。这种方法的优点是，CIS比CIGS具有更小的带隙，这使得可以在更大的波长范围内收集光子，从而导致更高的转换效率。此外，串联电池中使用的第二种材料是CH3NH3Pb(I1-xBrx)3，这是一种稳定的材料。相反，如果要使用CIGS作为低禁带材料，所需的CH3NH3Pb(I1-xBrx)3材料将需要使用非稳定浓度的溴。这两种单结太阳能电池都已经在首席研究员的实验室中制造出了高性能的电池。技术描述：我们实验室开发的最先进的CH3NH3PbI3钙钛矿型和铜铟硒(CIS)太阳能电池都将用于实现高性能串联电池，预计在单日照下效率超过30%。无镓太阳电池的带隙为1.0 eV，比传统的CIGS太阳电池和1.15 eV的硅基太阳电池更适合于实现基于钙钛矿结构的高效串联太阳电池。这是因为，对于带隙为1.15 eV的材料来说，最有效的串联太阳能电池是带隙为1.7-1.8 eV的材料。CH_3NH_3Pb(I_(1-x)Brx)_3的禁带宽度为1.74 eV，但不稳定。对于带隙为1.0 eV的材料，最佳的较高带隙为1.64 eV，对应于钙钛矿层CH3NH3Pb(I1-xBrx)3稳定的溴化物比例。在本项目中，将开发高效、环境稳定的CH3NH3Pb(I1-xBrx)3/CIS叠层太阳电池。我们将研究机械堆叠式和整体式钙钛矿型/顺式串联太阳能电池。该方法利用了已经在工业中得到验证的薄膜太阳能电池技术，并为高效、低成本的太阳能电池开辟了道路。

Abstract:Non-technical:Si is the dominant photovoltaic technology used around the world. These solar cells are assembled together to produce solar panels. They represent more than 90% of the solar panel market. The Si crystalline solar cells have demonstrated a maximum photovoltaic solar energy conversion efficiency of about 25% and this conversion efficiency has not improved very much over the last 10 years. On the other hand, tandem solar cells, where one utilizes a stack of two different materials with different band gaps, can lead to a sizable increase in the energy efficiency of solar cells, which would lead to a reduced number of required solar panels to generate the same amount of energy. The project is based on a solar cell made up of a thin layer of perovskite and a thin layer of copper-indium di-selenide (CIS) monolithically stacked together for a total thickness of order 2.5-3 µm, with an expected energy conversion efficiency approaching 30%. These solar cells would allow a quantum leap in energy conversion efficiency as compared to crystalline silicon solar cells. They would also allow the realization of flexible solar cells for many low cost applications. The tandem solar cell uses a chalcogenide material made up of three elements: Cu, In, and Se but does not use Ga as is typically done for single junction CIGS solar cell. The advantage of this approach is that CIS has a smaller bandgap than CIGS and this allows collecting photons over a larger wavelength range and therefore leads to a higher conversion efficiency. In addition, the second material used in the tandem cell is CH3NH3Pb (I1-xBrx)3, a material which is stable. On the contrary, if one would use CIGS as the low bandgap material, the required CH3NH3Pb (I1-xBrx)3 material would need to use a non-stable concentration of bromide. Both of these single junction solar cells have already been made in the Principal Investigator's laboratory with high performance. The challenge is to monolithically integrate both materials in an efficient tandem solar cell.Technical description:Both state-of-the-art CH3NH3PbI3 perovskite and Copper Indium Selenide (CIS) solar cells developed in our laboratory will be used to implement a high performance tandem cell with a predicted efficiency above 30% at one-sun illumination. The band gap of CIS (no gallium) solar cells is 1.0 eV and is more adapted than the traditional CIGS solar cell or silicon based solar cells with a bandgap of 1.15 eV to realizing high efficiency tandem solar cells based on perovskites. The reason is that the most efficient tandem solar cell for a material with a bandgap of 1.15 eV is a material with a bandgap of 1.7-1.8 eV. CH3NH3Pb(I1-xBrx)3 can be made to have a bandgap of 1.74 eV but has been found to be unstable. For a material with a bandgap of 1.0 eV, the optimum higher bandgap is 1.64 eV and corresponds to a proportion of bromide where the perovskite layer CH3NH3Pb(I1-xBrx)3 is stable. In this project, high efficiency, environmentally stable, CH3NH3Pb(I1-xBrx)3 /CIS tandem solar cells will be developed. Both mechanically stacked and monolithic perovskite/CIS tandem solar cells will be studied. The approach leverages thin film solar cell technology that has been validated in industry and opens up the way to highly efficient low cost solar cells.