有機高分子-無機矽奈米線混成太陽能電池之研究

Study of Organic polymer-Inorganic Si Nanowires Hybrid Solar Cells

林岱宏(Dai-Hong Lin)

指導教授 ： 林清富

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2010年)

https://doi.org/10.6342/NTU.2010.02949

摘要

有機導電高分子與無機半導體材料的結合對於光伏電池的可能應用吸引了許多關注。此主要是由於導電高分子薄膜有許多無機薄膜所沒有的優點，例如沒有晶格匹配問題、大面積覆蓋性、低溫製程容許性、簡易製程，及低成本等。因此，高分子/半導體異質接面結構對於進一步降低光伏元件成本被視為大有可為的。平面型高分子/半導體異質接面元件結構，只有接面附近的的光生載子能被有效地收集而不至於復合。為突破高分子/半導體異質接面太陽能電池的功率轉換效率，高分子/半導體奈米線異質接面結構被提議出來。由高分子覆蓋奈米線之結構大幅地增加放射狀方向的接面數，因此提高了電子電洞對分離後、復合前收集位於高分子與半導體界面處光生載子的機率。並且，使用矽奈米線可提供電子未被打擾的傳導路徑，矽奈米線結構更能有效抑制光學反射，並增加材料的光學吸收。這些性質能夠改善高分子/半導體異質接面太陽能電池的功率轉換效率。
我們以低成本、低溫製程且製程簡單的金屬輔助化學濕蝕刻方式，去製作大面積的矽奈米線，以此方式所製備的矽奈米線能保有原矽晶片的高品質單晶的優點，並探討蝕刻時間對矽奈米線長度、形態，以及其對於反射率的影響。
為了改善金屬輔助化學濕蝕刻對於較長矽奈米線所產生的聚集成束現象，我們發展二次金屬輔助化學濕蝕刻法，先沉積銀粒子於矽晶圓表面，後以蝕刻溶液藉銀粒子垂直向下蝕刻，製備出大面積且均勻分布的矽奈米線陣列。
最後呈現出矽奈米線/poly(3,4-ethylenedioxy thiophene)/poly(styrenesulfonate) (PEDOT:PSS)異質接面太陽能電池，我們觀察到奈米線結構型異質接面太陽能電池之光伏表現較平面型有明顯改善。為呈現此效應，一大面積矽奈米線陣列藉金屬輔助化學濕蝕刻製作於n型矽基板上，並以PEDOT:PSS旋塗於矽奈米線上製成異質接面，於寬頻可見光照射下對其作電流對電壓量測觀察。

關鍵字

矽奈米線 ； 有機導電高分子 ； 金屬輔助化學濕蝕刻 ； 異質接面 ； 混成太陽能電池

並列摘要

The combination of electrically conductive polymers and semiconductor materials attracts lots of interests for possible applications in photovoltaic devices. It is mainly because the conductive polymer thin films have several advantages over inorganic thin films such as no lattice mismatch problem, large-area coverage, low-temperature process-capability, easy preparation, low cost, etc. Therefore, the polymer/semiconductor heterojunction structure is promising to further lower the cost of photovoltaic devices. However, with a planar polymer/semiconductor device structure, only the photogenerated carriers near that junction can be collecting efficiently without recombination.
To break the limit of the power conversion efficiency of polymer/semiconductor heterojunction solar cells, the polymer/semiconductor nanowire heterojunction structure was proposed. The nanowire structure covered with polymer greatly increases the number of junctions in the radial directions, thus enhancing the probability of collecting photogenerated carriers at the interface after separation of hole-electron pair and before recombination. Furthermore, silicon nanowires (SiNWs) provide an uninterrupted conduction path for electron transport, and the silicon nanowire structure will suppress the optical reflectance and enhance the optical absorption of materials. These properties will improve the power conversion efficiency of polymer/semiconductor heterojunction solar cells.
We use metal-assisted etching, which contains several advantages, such as low-temperature process-capability, easy preparation, low cost, to fabricate large area, well-aligned silicon nanowires (Si NWs) from Si wafer. Si NWs fabricated by this method keep the properties of single-crystalline quality. Some discussions on morphology by SEM images and optical reflectance of Si NWs would be reported.
To overcome the drawbacks of the silicon bundles from longer silicon nanowires fabricated by metal-assisted etching, we develop ‘two times metal-assisted etching’ to fabricate large area, uniform-spreading silicon nanowire arrays.
We demonstrate silicon nanowires (Si NWs)/ poly(3,4-ethylenedioxy thiophene) /poly(styrenesulfonate) (PEDOT:PSS) heterojunction solar cells. We observe that the photovoltaic behavior of heterojunction solar cells improves remarkably. To demonstrate this, heterojunctions obtained by coating n-type silicon nanowires with PEDOT:PSS are investigated by means of current versus voltage measurements, which were performed under broad band visible light irradiation. Some discussions on combination of Si NWs and PEDOT:PSS by TEM images and optical reflectance of solar cells would be reported.

並列關鍵字

silicon nanowire ； polymer ； metal-assisted etching ； heterojunction ； hybrid solar cells

參考文獻

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