ZnO:X透明导电膜的调制掺杂生长与氢化处理的研究

ZnO-TCO is thought to have potential value to replace ITO and FTO using in solar cell front electrode, because of its low-cost, environmental protection and stable performance. At present, the ZnO-TCO still exists the following problems: (1) The transmittance is low in the infrared spectrum domain; (2) The native crater-like texturing is prepared by magnetron sputtering is not breakthrough; (3) The potential barrier is too high between the ZnO-TCO and the cell window layer. According to the element can improve the carrier mobility and have similar ionic radius with Zn2+, so this project put forward X doped ZnO was prepared by magnetron sputtering (X is an appropriate doping element). The band structure have arrived at change via doped or the resilience of thin film, which could eliminate or splitting of degenerate energy level; meanwhile, that reduce the carrier effective mass and improve ZnO:X film layer mobility; finally, the constraint problem was solved between visible - infrared wavelengths of light transmittance and conductivit. Through the X-H co-doped, this can change the ZnO surface dipole and polar crystal plane, so that thin-film vacuum level move upwards; which solved the Schottky barrier height between the ZnO-TCO and the window layer. By hydrogen plasma etching and sputter particle bombardment transition loose layer on the surface, which obtain the native crater-like texturing on the films surface. This method of modulation doping and hydrogenation process is the innovative of this project.

ZnO-TCO因其廉价、环保和性能稳定，有望取代ITO和FTO应用在太阳电池前电极，有着巨大的潜在应用价值。但目前还存在如下问题 ：（1）红外光谱域光透过率低；（2）磁控溅射直接制备陨石坑状绒面难点仍未突破；（3）与电池窗口层之间势垒过高。本项目提出用磁控溅射方法，按有利于提高载流子迁移率原则，从高掺杂效率和与Zn2+半径相近角度考察选择合适的掺杂源X，通过调 制掺杂或薄膜层的应变力，改变能带结构，消除或劈裂简并能级，减小载流子有效质量，提高ZnO：X薄膜层迁移率，解决可见-红外光波段光透过率和导电性相制约问题。通过对ZnO：X薄膜层的氢化，生长ZnO: X-H过渡疏松层，出现（0001）极性面，吸附氧，上移真空能级，解决ZnO: X-H与电池窗口层之间势垒过高问题。通过氢等离子体刻蚀和溅射粒子轰击过渡疏松层表面，直接生长陨石 坑绒面。这种调制掺杂和氢化处理的方法，体现了本项目的创新性。

ZnO-TCO因其廉价、环保和性能稳定，有望取代ITO和FTO应用在太阳电池前电极，有着巨大的潜在应用价值。但目前还存在如下问题 ：（1）红外光谱域光透过率低；（2）磁控溅射直接制备陨石坑状绒面难点仍未突破；（3）与电池窗口层之间势垒过高。为了解决这些问题，首先总结归纳了前期工作成果，初步确定了W和Ga为掺杂元素。然后，采用调制掺杂方法，分别研究了ZnO:W和ZnO: Ga透明导电薄膜的导电性、透光性，以及表面性能。通过溅射功率调制掺杂制备的ZnO:W薄膜，可将薄膜高透光性拓展至可见-红外光谱域（400-1500纳米范围内的平均透光率超过85%），且电学性能良好（约6.69×10−3Ωcm）。然而，其电学性能仍然偏低，未能实现陨石坑绒面的本征制备。为了进一步研究薄膜表面的绒面生长特性和界面特性，在分别研究了靶间、溅射功率、溅射气压、氩气流量和沉积时间等调制掺杂对制备ZnO: Ga薄膜性能影响的基础上，通过正交试验方法，确定了最优化的调制掺杂方案。根据优化后的调制掺杂方案和氢化处理方法制备的ZnO: Ga薄膜，测试结果表明：薄膜样品在光波段450nm-2000nm平均透光率为83%，电阻率为6.03×10-4Ω·cm， ZnO: Ga薄膜表面具有陨石坑绒面结构，且界面性能明显改善。通过项目研究，解决了传统ITO 和FTO透明导电薄膜在红外光谱域的光透过率低的问题。同时，解决了传统透明导电薄膜陨石坑状绒面本征制备和界面问题，使得ZnO-TCO有望取代传统ITO 和FTO 应用在太阳电池前电极，有着巨大的潜在应用价值。