矽基太陽能電池的轉換效率，主要受限於兩類的能量損耗，其中一類是光子能量遠高於材料能隙時造成聲子散射的效應減少光能轉換成電能的機率形成熱能而散失。所以本論文探討的主題是利用成長矽量子點於氮化矽基質中取代一般氮化矽抗反射膜作為一光子轉換層，將高能量光子透過量子點轉換成低能量光子再吸收，預期能提升光子吸收機率，進而增加太陽能電池轉換效率。實驗中利用PECVD，通入SiH4和NH3作為反應氣體，改變NH3氣體的流量，當過量的Si原子無法和N原子反應析出形成結晶矽量子點。 藉由NH3流量的調變，改變了矽量子點的尺寸，造成矽量子點發光波長的變化。低NH3流量有較大矽量子點尺寸而發光波長較長，也就是能隙較小。沉積功率對矽量子點生成的大小只有微幅調變的效應，發光頻譜差異不大，低功率下發現發光強度較強。對矽量子點影響較大的因素是沉積溫度，低沉積溫度下矽量子點發光頻譜向短波長移動，也就是矽量子點尺寸較小，但膜層折射率較低符合抗反射層需求。 選用SiH4/NH3流量比為120/10 sccm、100℃和50W的條件沉積矽量子點抗反射膜於多晶矽太陽能電池上，效率的量測結果顯示，轉換效率達到12.12%，提升了百分之11％。The best conversion efficiency reported for crystalline Si solar cell is about 25%, which is very close to the theoretical limit. This limitation is the result of energy-loss processes inherent to the semiconductor materials and it can be divided into two categories. One of them is the high-energy losses resulting from the loss of excess energy of photogenerated carriers, as a consequence of phonon scattering. So, in this thesis we want to use a non-stoichiometric Silicon nitride layer containing Si quantum dots as photon-down converter which can convert high-energy photons into lower energy photons more easily absorbed by Si solar cell. We also want this layer to replace traditional SiN anti- reflection coating of Si-based solar cell. In the experiment process, we use SiH4 and NH3 as reaction gas to form Si quantum dots in SiN matrix. Decreasing the NH3 gas flow rate which increase the size of Si quantum dots. Larger size of Si quantum dot has smaller energy band gap so the larger size of Si quantum dot has longer wavelength of excitation light. The RF power has light influence on Si quantum dot formation but low RF power condition has stronger intensity of excitation light. The deposition temperature influence the formation of Si quantum dot seriously. In the low deposition temperature condition, the excitation light wavelength of Si quantum dots shift to short wavelength region and the refraction index of the film is much smaller that adaptable for anti-reflection layer of Si-based solar cell. By applying Si-rich Nitride film to anti-reflection layer of multi-crystalline Si solar cell, the conversion efficiency increase from 10.9% to 11.12%。
