新型高效TMO/c-Si诱导型异质结太阳电池研究

The induced heterojunction solar cell with ultra high and low work function materials as the emitter and back surface field separately, caused the movement of Fermi level close to the valence or conduction band which resulted in obtaining carrier’s selective contact on the silicon surface, is becoming an international research hotspot due to its low temperature and doping-free characteristics. Based on the previous work of MLBC (multilayer films back contact) solar cell, in this project, a novel type of high efficiency TMO /c- Si induced heterojunction solar cells was proposed. In order to explore the emitter's optical and electrical characteristics of TMO/Si solar cells, we focus on exploring the new transition metal oxide materials (TMO) such as CrO3, Co2O5, Ag2O and other materials. And the characteristic performance, numerical simulation and stability of the novel high efficiency TMO / c-Si solar cells will be further studied. In particular, the methods of the bulk and emitter passivation as well as the interface defects controlling will be explored. The efficiency loss mechanism will be established by the careful study of TMO/c-Si contact interface, the formation of p-n junction space charge region and the contact resistance loss. Finally, the ultimate efficiency of TMO/Si solar cells will be predicted by the numerical simulation. On the basis of the above research work, the efficiency of front junction and HBC structure crystalline silicon solar cells can exceed 22%, and the mechanical stacked solar cell efficiency reaches 26%. This research will establish the foundations to explore the industrialization technology of TMO/c-Si heterojunction solar cells with independent intellectual property rights, simple preparation process and high efficiency.

诱导型异质结太阳电池是采用极高和极低功函数薄膜材料作为发射极和背场，诱导费米能级的移动而获得载流子选择性接触，该电池具有低温、免掺杂特点成为国际研究热点。本项目是课题组在首次提出MLBC（multilayer films back contact）太阳电池基础上，提出新型高效TMO/c-Si诱导型异质结太阳电池研究。重点研究新型过渡金属氧化物（TMO）如CrO3、Co2O5、Ag2O等作为太阳电池发射极；开展新型TMO/c-Si诱导型异质结太阳电池器件性能、结构理论及工艺研究，解决器件接触界面及体区钝化。在上述工作基础上，将TMO与HBC晶体硅高效电池结构结合，制备出高效TMO/c-Si异质单结和机械叠层太阳电池。制备的TMO/c-Si异质结太阳电池单结和叠层效率分别达到22%和26%。为探索具有自主知识产权、制备工艺简单、高效TMO/c-Si异质结太阳电池的产业化技术奠定基础。

钝化接触太阳电池由于同时钝化c-Si表面而又选择性地提取一种载流子（即电子或空穴）的接触结构，该结构可以同时降低电池复合电流J0 和接触电阻ρc 而成为近几年光伏研究领域的一个热点。不同于传统的HJT和TOPCon太阳电池，TMO/Si异质结利用高、低功函数薄膜材料与晶体硅结合形成异质结接触结构，诱导硅能带弯曲，从而形成载流子选择性提取，是一种新型的载流子选择接触电池结构。该电池结构避免了高温、掺杂等工艺，从而具有低温制备、工艺简单、低成本和全面积实现钝化接触等优势具有较高的研究价值和应用前景。.本项目首先研究了多种不同的TMO薄膜材料、TMO多层膜的制备和表征，筛选出了WO3、MoOx、V2O5等多种不同薄膜材料作为发射极；采用热蒸发工艺制备TMO作为空穴选择性接触，重点研究了TMO/Si 异质结空穴选择性接触性能；实现低温、免掺杂TMO /硅异质太阳电池的制备，并在国际上首次提出TMO叠层/硅异质太阳电池结构，开展了TMO/Si 异质结太阳电池的数值模拟与机理研究；在上述工作基础上，为开展全免掺杂TMO/硅异质结太阳电池，重点开展低功函数的金属卤族化物如EuF3、CeF3、CsI和硫化物InS、SiC等电子选择性材料，并对异质结电子选择性接触特性进行了充分研究，接触电阻最小可以达到10 mΩ·cm2 (CsI/n-Si)；最终实现了新型的全免掺杂TMO/硅异质结太阳电池，并优化了电池制备工艺；用于免掺杂结构的TMO叠层/硅异质太阳电池的最高效率达到了22.4%。采用a-Si薄膜钝化的TMO/硅异质结太阳电池效率已超过23.5%；利用微晶SiC作为电子选择性接触和导电薄膜材料的异质结太阳电池效率为24%；最后，探索了MoOx多层膜组成TMO/硅异质结太阳电池和钙钛矿叠层太阳电池，最终效率达到25.5%。.该项目研究不仅丰富了载流子选择性接触材料研究领域，而且建立了新型全免掺杂背接触电池结构，并解决了金属和半导体之间的费米钉扎效应影响，深化了载流子传输与复合接触太阳电池理论，因此该项目的研究成果具有十分重要的科学意义和实际的应用前景。