陽極緩衝層對於小分子有機太陽能電池特性研究

在本研究中，第一部分以CuPc 和C60製作異質接面之有機太陽能電池，分別調變CuPc、C60、BCP之厚度以達到激子在薄膜之最佳擴散長度及激子阻隔厚度，從實驗得知元件參數為ITO/CuPc(100 nm)/C60(50 nm)/BCP(10 nm)/Al(90 nm)，元件最佳特性為Voc=0.38 V，Jsc=3.09 mA/cm2，F.F.=59.6，%, η=0.7 %。論文第二部分研究於PEDOT:PSS 中加入不同濃度的Glycerol 或Dimethyl sulfoxide作為添加物，並對於改質後PEDOT:PSS 的光性、物性與電性進行探討。而在PEDOT:PSS 中加入適當濃度的添加物，會使導電度有提升的現象；最後表面成膜粗糙度會隨著添加物的濃度增加而增加，使得旋轉塗佈方式容易有成膜不均的現象。最後將改質後的PEDOT:PSS 作為陽極緩衝層，應用於有機小分子太陽能電池元件上，其元件最佳結構為ITO/G-PEDOT:PSS(40 nm)(加入4 %濃度的甘油)/CuPc(100 nm)/C60(50 nm)/BCP(10 nm)/Al(90 nm)，元件最佳特性為Voc=0.44 V, Jsc=9.38 mA/cm2, F.F.=32.38 %, η=1.33 %。光電轉換效率可從0.7 %提升至1.33 %，短路電流密度大幅提升32 %。探討其改善原因為加入添加物使得導電度增加，造成短路電流密度增加，最後提升整體有機小分子太陽能電池元件的光電轉換效率。

關鍵字

異質接面；有機薄膜；甘油；碳60 ；銅酞

並列摘要

In the study, Heterojunction organic thin film photovoltaic devices composed of copper phtalocyanine (CuPc) and fullerene (C60) were inverstigated, the optimal diffusion length of excition is obtained through the modification of CuPc, C60, BCP thickness, respectively. The device consists of ITO/CuPc/C60/BCP/Al, where the electron acceptor layer C60 (50 nm) and exciton barrier layer BCP (10 nm) are the optimum exciton diffusion length and exciton barrier thickness respectively. The short current density Jsc has been studied by changing the thickness of donor layer CuPc from 80 to 110 nm. we can see when the thickness of CuPc at 100 nm it has the maximum short current density of 3.09 mA/cm2, thus the diffusion length of exciton in CuPc is approx. 100 nm. While if the thickness of CuPc is too thin will result in less exciton as generated after phototherapy which reduces the exciton in decomposing into electrons and holes and lowers the short current as well. If the thickness of CuPc exceeds the diffusion length, the exciton will have difficulties in diffusing to the p-n junction and decomposing into electrons and holes which reduces the short current density. The devices has the optimum structure and properties: ITO/CuPc(100 nm)/C60(50 nm)/BCP(10 nm)/Al(90 nm)，Voc=0.38 V，Jsc=3.09 mA/cm2，F.F=59.6 %，η=0.7 %。 In the study, investigated the different percentage of glycerol doped into PEDOT:PSS as anode buffer layer in OSC. The electrical, optical and physical properties of PEDOT:PSS were measured before and after adding glycerol Modified PEDOT:PSS with proper concentration addition increased its conductivity. Finally, surface roughness of PEDOT:PSS layer increased with higher concentration of addition resulted in bad film-forming from spin coating process. We fixed the doping 6 % glycerol first, then change the spin coating rpm of G-PEDOT:PSS from 4500 to 6000. we know when the rpm of G-PEDOT:PSS at 5500, there is the max. short current density of 6.1 mA/cm2 with conversion efficiency of 0.88 %. While rpm less than 5500 with thicker G-PEDOT:PSS will result in the increase of device equivalent circuit series resistance (Rs), which reduces the short current density. When rpm is more than 5500, due to the thickness of hole buffer layer is too thin that the hole buffer layer with poor efficiency of collection hole and results in low current density and efficiency. We fixed the G-PEDOT:PSS rpm at 5500 and varied the concentration of glycerol in PEDOT:PSS from 3 to 6 %. When the concentration of glycerol less than 4%, we can see that the conductivity of G-PEDOT:PSS layer is lower which increase the component equivalent circuit series resistance and lower the short current density. If the concentration of glycerol exceeds 4%, though the conductivity of G-PEDOT:PSS layer is higher, the surface roughness has reached to ITO level will influence the flatness and the evenness of organic layer as evaporation coated, which results in electronic holes difficult in transferring to ITO after decomposing, thus reduces the device short current density and efficiency. We fixed the G-PEDOT:PSS rpm at 5500 and varied the concentration of glycerol in PEDOT:PSS from 20 to 50 %. When doping DMSO at 25% the component has the optimum efficiency due to conductivity increased. Show when DMSO doped up to 33% and 50%, due to over-saturated caused the poor thin film surface in spin-coating and resulted in the component efficiency decreased. We fabricated small molecular solar cells with modified PEDOT:PSS as anode buffer layer. The devise was consisted of ITO/PEDOT:PSS (40 nm)(doping concentration of glycerol)/CuPc(100 nm) /C60(50 nm)/BCP(10 nm)/Al(90 nm). The devices has the optimum properties:Voc=0.38 V，Jsc=3.09 mA/cm2，F.F=59.6 %，η=0.7 %. We found that improvement of power conversion efficiency of small organic solar cell from 0.7% to 1.33% and short-circuit current was improved for 33%, with modified PEDOT:PSS as anode buffer layer. We suggested that the improved short-circuit current was originated from increased conductivity of PEDOT:PSS that was modified by glycerol or Dimethyl sulfoxide. Finally power conversion efficiency of small organic solar cell was increased with modified.