激光晶化制备硅量子点/碳化硅多层膜p-i-n结构的光伏特性探索

Fabrication and photovoltaic properties of laser crystallized p-i-n structures based on Si quantum dots/SiC multilayers

对不同能量密度激光晶化的硅量子点/碳化硅周期性多层膜的结构与光学性质进行了研究.结果表明,激光晶化技术可以获得晶化的硅量子点并且保持良好的周期性层状结构;随着激光能量密度的增大,多层膜中的硅量子点的晶化率和晶粒尺寸都随之增大,光吸收系数增强,吸收边红移,光学带隙减小.进而初步尝试了对在镀有氧化铟锡(ITO)透明导电电极的玻璃衬底上制备的基于硅量子点/碳化硅周期性多层膜的全硅量子点太阳能电池光伏性能的探索,提出利用KrF准分子脉冲激光晶化技术代替传统的高温退火技术来获得全硅量子点电池的方法,以避免长时间的高温过程对玻璃衬底和ITO膜的破坏,获得了有效面积为0.8cm2的电池.研究发现激光晶化技术制备的全硅量子点电池具有良好的整流特性,并且随着激光能量密度的增大,电池的外量子效率先增大后减小,170mJ·cm^(-2)是最佳的激光晶化能量密度,基于此条件制备的全硅量子点电池初步获得了0.16mA·cm-2的短路电流密度.

Periodical Si quantum dots（QDs）/SiC multilayers were obtained by using the laser induced crystallization technique and the structural and optical properties were studied. The cross-sectional TEM measurements were performed to characterize the microstructures of laser-crystallized Si QDs/SiC multilayers. The periodically layered structures are well kept and the formation of Si QDs in a-Si layers can be clearly identified. It is found that with increasing the laser fluence, both the crystallinity ratio and the average dot size were increased. The optical absorption coefficient is gradually increased and optical band gap decreased accordingly. The p-i-n structures based on laser crystallized Si QDs/SiC multilayers on the Indium Tin Oxide （ITO）transparent electrode coated glass substrates were fabricated to get all-Si QDs-based solar cells containing Si QDs/SiC multilayers. KrF pulsed excimer laser was used to crystallize a-Si layer to form Si QDs, which could avoid damaging the ITO layer and the glass substrates during the long time high-temperature annealing process. The cell area was about 0. 8 cm2. The rectification characteristics was observed and the rectification ratio reached to 102 at the applied voltage V= d：2 V, which indicated that the p-i-n structures are well formed with the laser crystallization method. The photovoltaic properties of all-Si QDs-based solar ceils containing Si QDs/SiC multilayers were studied. It is worth noting that the external quantum efficiency（EQE）of ail-Si QDs-based solar ceils were located the spectral range of 300~700 nm and were influenced by different laser fluence, which must be controlled in a proper range. It is found that 170 mJ. cm-2 is the most suitable laser fluence. The short circuit current density（J~ ）and the open circuit voltage（V~ ）obtained in the 170 mJ. cm 2 laser crystallized-solar cell was 0. 16 mA. cm 2 and 287 mV, respectively. These results laid a foundation for further research based on all-Si QDs-based solar cells.