石墨相氮化碳的功能化及其在聚合物太阳能电池和光催化中的应用
发布时间：2018-09-01 07:19
【摘要】：聚合物太阳能电池是一种基于有机光活性材料的光伏器件,因具有制备工艺简单、成本低、重量轻且可大规模制备成柔性器件等优点而备受青睐。石墨相氮化碳因其特殊的电子能带结构以及良好的物理化学稳定性等特点,在光催化领域已经得到了广泛的应用,而在聚合物太阳能电池中却鲜有报道。本论文以探索石墨相氮化碳(g-C_3N_4)在聚合物太阳能电池中的应用以及提升其光催化性能为出发点,集中于对g-C_3N_4进行简单的功能化以拓展其应用,主要开展了以下四个方面的工作:(1)为提高g-C_3N_4在邻二氯苯溶剂中的分散性,我们首先通过溶剂热法制备了可溶液加工的C_3N_4量子点,然后将其掺杂到P3HT:PC61BM,PBDTTT-C:PC_(71)BM和PTB7-Th:PC_(71)BM三种不同光活性层体系中。所获得的反型体相异质结聚合物太阳能电池的能量转换效率分别达到了 4.23%,6.36%和9.18%,相对于未掺杂的参比电池器件分别提升了约17.5%,11.6%和11.8%,这一提升主要来源于短路电流(Jsc)的提升。通过对C_3N_4量子点掺杂前后活性层薄膜的表面形貌,光吸收和光致发光性质以及电池器件的电荷传输性质等一系列表征,表明C_3N_4量子点的掺杂改善了光活性层的形貌以及电荷在活性层及界面的分离和传输,从而提升了电池器件的性能。(2)为拓展g-C_3N_4在聚合物太阳能电池中的应用,我们通过改变溶剂热法所使用的溶剂,制备出了极性溶剂N,N-二甲基甲酰胺(DMF)中分散性较好的C_3N_4量子点,然后将其旋涂在ZnO薄膜上用于修饰ZnO电子传输层,在此基础上制备的基于 PBDTTT-C:PC_(71)BM,PTB7:PC_(71)BM 和 PTB7-Th:PC_(71)BM 三种不同光活性层体系的反型体相异质结聚合物太阳能电池的能量转换效率分别达到了7.03%,8.47%和9.29%,与基于未修饰的ZnO参比电池器件相比分别提升了约20.0%,12.2%和11.1%。电池器件的提升主要来源于短路电流(Jsc)的提高,这是由于C_3N_4量子点修饰ZnO后改善了 ZnO电子传输层的形貌,并降低了 ZnO的功函数,这有利于电子在光活性层和ZnO电子传输层界面的收集和传输。(3)作为与g-C_3N_4结构非常类似的另一类热门的二维材料,石墨烯已在聚合物太阳能电池中得到了广泛的应用,主要集中于将其应用于聚合物太阳能电池的空穴传输层。为替代正型体相异质结聚合物太阳能电池中常用的酸性PEDOT:PSS空穴传输层,我们发展了一种简单的修饰氧化石墨烯提高其空穴传输能力并应用于正型体相异质结聚合物太阳能电池的方法。我们首先在氧化石墨烯薄膜上旋涂了一层磷化物,发现磷元素修饰后的氧化石墨烯(P-GO)可以有效地替代PEDOT:PSS空穴传输层。以P-GO作为新型空穴传输层,基于三种不同的光活性层体系 PTB7:PC_(71)BM,PBDTTT-C:PC_(71)BM 和 P3HT:PC61BM 的正型体相异质结聚合物太阳能电池的能量转换效率分别达到7.85%,6.56%和3.75%,与相应的基于PEDOT:PSS空穴传输层的电池器件的效率相当。原子力显微镜和水接触角测试表明磷修饰有利于光活性层与GO空穴传输层的界面接触。紫外光电子能谱,X射线光电子能谱以及拉曼光谱揭示了磷修饰可以实现p型掺杂,从而增加了氧化石墨烯的功函数,使其与活性层形成了更好的欧姆接触。这两方面性能的改善使得电池器件的开路电压和填充因子相比于以未修饰的GO作为的空穴传输层器件得到了明显的提升,进而提高电池器件的能量转换效率。(4)由于石墨相氮化碳(g-C_3N_4)的带隙较宽以及层间接触电阻较大等原因,其可见光催化活性十分有限。为提高g-C_3N_4的电荷分离效率和导电性,我们发展了一种简单的利用富勒烯C_(60)共价修饰g-C_3N_4的方法。我们首先采用高能球磨法成功合成了 g-C_3N_4与C_(60)共价连接的g-C_3N_4/C_(60)杂化材料。通过一系列光谱表征,证实了 g-C_3N_4/C_(60)杂化结构的形成,并提出了一种可能的g-C_3N_4/C_(60)杂化材料的构型,即通过四元碳氮杂环将富勒烯C_(60)连接到g-C_3N_4的边缘。然后将g-C_3N_4/C_(60)杂化材料应用于可见光(λ420 nm)下分解水产生氢气,在没有使用包括Pt在内的任何贵金属助催化剂的条件下,我们获得了 266 μmol·h-1g-1的产氢速率,相比于未修饰的g-C_3N_4(67μmol·h-1g-1)提高了大约4倍。通过C_(60)共价修饰提高g-C_3N_4的光催化活性的原因是C_(60)共价连接降低了 g-C_3N_4的导带,有利于电子从光敏剂转移到g-C_3N_4上,同时光生电子从g-C_3N_4到C_(60)的快速转移有效地阻止了光生电子-空穴对的复合。
[Abstract]:Polymer solar cell is a kind of photovoltaic device based on organic photo-active materials. It has many advantages, such as simple preparation process, low cost, light weight and large-scale preparation of flexible devices. Graphite-phase carbon nitride is widely used in photocatalysis because of its special electronic band structure and good physical and chemical stability. Graphite phase carbon nitride (g-C_3N_4) has been widely used in polymer solar cells, but rarely reported in polymer solar cells. In this paper, the application of graphite phase carbon nitride (g-C_3N_4) in polymer solar cells and the enhancement of its photocatalytic performance were explored, focusing on the simple functionalization of g-C_3N_4 to expand its application. In order to improve the dispersion of g-C_3N_4 in o-dichlorobenzene solvents, we first prepared the soluble C_3N_4 quantum dots by solvothermal method, and then doped them into three different photoactive layer systems: P3HT: PC61BM, PBDTTT-C: PC_ (71) BM and PTB7-Th: PC_ (71) BM. The energy conversion efficiencies of the batteries are 4.23%, 6.36% and 9.18% respectively, which are 17.5%, 11.6% and 11.8% higher than those of the undoped reference batteries. This improvement is mainly due to the improvement of short-circuit current (Jsc). The surface morphology, optical absorption and photoluminescence properties of the active layer films before and after C 3N 4 quantum dot doping are studied. A series of characterizations, such as the charge transfer properties of the cell devices, show that the doping of C 3N 4 quantum dots improves the morphology of the photoactive layer and the separation and transmission of charge at the active layer and interface, thus improving the performance of the cell devices. (2) To expand the application of g-C 3N 4 in polymer solar cells, we changed the solvothermal method. C_3N_4 quantum dots with good dispersion in polar solvents N, N-dimethylformamide (DMF) were prepared and spin-coated on ZnO thin films to modify the ZnO electron transport layer. On this basis, three inverters based on PBDTTT-C:PC_ (71) BM, PTB7:PC_ (71) BM and PTB7-Th BM and PTB7-PC_ (71) BM were prepared. The energy conversion efficiency of phase heterojunction polymer solar cells is 7.03%, 8.47% and 9.29% respectively, which is about 20.0%, 12.2% and 11.1% higher than that of unmodified ZnO reference cells. The improvement of cell devices is mainly due to the improvement of short circuit current (Jsc), which is attributed to the improvement of ZnO electrons by C_3N_4 quantum dots modified ZnO. The morphology of the transport layer and the reduction of the work function of ZnO are beneficial to the collection and transmission of electrons at the interface between the photoactive layer and the ZnO electron transport layer. (3) Graphene has been widely used in polymer solar cells as another popular two-dimensional material with similar structure to g-C_3N_4, mainly focusing on its application in polymer solar cells. In order to replace the acidic PEDOT: PSS hole transport layer commonly used in normal bulk heterojunction polymer solar cells, we developed a simple method to modify graphene oxide to improve its hole transport capacity and apply it to normal bulk heterojunction polymer solar cells. It was found that the modified graphene oxide (P-GO) can effectively replace the PEDOT:PSS hole transport layer by spin coating the graphene oxide film with phosphides. The orthotropic phase heterojunction polymerization of P-GO as a novel hole transport layer based on three different photoactive layer systems PTB7:PC_ (71) BM, PBDTTT-C:PC_ (71) BM and P 3HT:PC61BM was carried out. The energy conversion efficiencies of solar cells are 7.85%, 6.56% and 3.75% respectively, which are comparable to the corresponding devices based on PEDOT:PSS hole transport layer. The results of atomic force microscopy and water contact angle test show that phosphorus modification is beneficial to the interface between the photoactive layer and the GO hole transport layer. Raman spectroscopy reveals that phosphorus modification can achieve p-type doping, thus increasing the work function of graphene oxide and forming a better ohmic contact with the active layer. (4) The visible photocatalytic activity of graphite carbon nitride (g-C_3N_4) is very limited due to its wide band gap and large contact resistance between layers. To improve the charge separation efficiency and conductivity of g-C_3N_4, a simple covalent modification of fullerene C_ (60) has been developed. The g-C_3N_4/C_ (60) hybrid material covalently bonded with g-C_3N_4 and C_ (60) was synthesized by high energy ball milling. The formation of g-C_3N_4/C_ (60) hybrid structure was confirmed by a series of spectral characterization, and a possible configuration of g-C_3N_4/C_ (60) hybrid material was proposed. Leene C_ (60) is connected to the edge of g-C_3N_4. Then g-C_3N_4/C_ (60) hybrid material is applied to decompose water to produce hydrogen under visible light (lambda 420 nm). Without any precious metal cocatalyst including Pt, the hydrogen production rate of 266 micromol h-1g-1 is obtained, which is higher than that of unmodified g-C_3N_4 (67 micromol h-1g-1). The photocatalytic activity of g-C_3N_4 was enhanced by C_ (60) covalent modification because C_ (60) covalent bonding reduced the conduction band of g-C_3N_4, facilitated the transfer of electrons from photosensitizer to g-C_3N_4, and the rapid transfer of photogenerated electrons from g-C_3N_4 to C_ (60) effectively prevented the recombination of photogenerated electron-hole pairs.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM914.4
本文编号：2216502
[Abstract]:Polymer solar cell is a kind of photovoltaic device based on organic photo-active materials. It has many advantages, such as simple preparation process, low cost, light weight and large-scale preparation of flexible devices. Graphite-phase carbon nitride is widely used in photocatalysis because of its special electronic band structure and good physical and chemical stability. Graphite phase carbon nitride (g-C_3N_4) has been widely used in polymer solar cells, but rarely reported in polymer solar cells. In this paper, the application of graphite phase carbon nitride (g-C_3N_4) in polymer solar cells and the enhancement of its photocatalytic performance were explored, focusing on the simple functionalization of g-C_3N_4 to expand its application. In order to improve the dispersion of g-C_3N_4 in o-dichlorobenzene solvents, we first prepared the soluble C_3N_4 quantum dots by solvothermal method, and then doped them into three different photoactive layer systems: P3HT: PC61BM, PBDTTT-C: PC_ (71) BM and PTB7-Th: PC_ (71) BM. The energy conversion efficiencies of the batteries are 4.23%, 6.36% and 9.18% respectively, which are 17.5%, 11.6% and 11.8% higher than those of the undoped reference batteries. This improvement is mainly due to the improvement of short-circuit current (Jsc). The surface morphology, optical absorption and photoluminescence properties of the active layer films before and after C 3N 4 quantum dot doping are studied. A series of characterizations, such as the charge transfer properties of the cell devices, show that the doping of C 3N 4 quantum dots improves the morphology of the photoactive layer and the separation and transmission of charge at the active layer and interface, thus improving the performance of the cell devices. (2) To expand the application of g-C 3N 4 in polymer solar cells, we changed the solvothermal method. C_3N_4 quantum dots with good dispersion in polar solvents N, N-dimethylformamide (DMF) were prepared and spin-coated on ZnO thin films to modify the ZnO electron transport layer. On this basis, three inverters based on PBDTTT-C:PC_ (71) BM, PTB7:PC_ (71) BM and PTB7-Th BM and PTB7-PC_ (71) BM were prepared. The energy conversion efficiency of phase heterojunction polymer solar cells is 7.03%, 8.47% and 9.29% respectively, which is about 20.0%, 12.2% and 11.1% higher than that of unmodified ZnO reference cells. The improvement of cell devices is mainly due to the improvement of short circuit current (Jsc), which is attributed to the improvement of ZnO electrons by C_3N_4 quantum dots modified ZnO. The morphology of the transport layer and the reduction of the work function of ZnO are beneficial to the collection and transmission of electrons at the interface between the photoactive layer and the ZnO electron transport layer. (3) Graphene has been widely used in polymer solar cells as another popular two-dimensional material with similar structure to g-C_3N_4, mainly focusing on its application in polymer solar cells. In order to replace the acidic PEDOT: PSS hole transport layer commonly used in normal bulk heterojunction polymer solar cells, we developed a simple method to modify graphene oxide to improve its hole transport capacity and apply it to normal bulk heterojunction polymer solar cells. It was found that the modified graphene oxide (P-GO) can effectively replace the PEDOT:PSS hole transport layer by spin coating the graphene oxide film with phosphides. The orthotropic phase heterojunction polymerization of P-GO as a novel hole transport layer based on three different photoactive layer systems PTB7:PC_ (71) BM, PBDTTT-C:PC_ (71) BM and P 3HT:PC61BM was carried out. The energy conversion efficiencies of solar cells are 7.85%, 6.56% and 3.75% respectively, which are comparable to the corresponding devices based on PEDOT:PSS hole transport layer. The results of atomic force microscopy and water contact angle test show that phosphorus modification is beneficial to the interface between the photoactive layer and the GO hole transport layer. Raman spectroscopy reveals that phosphorus modification can achieve p-type doping, thus increasing the work function of graphene oxide and forming a better ohmic contact with the active layer. (4) The visible photocatalytic activity of graphite carbon nitride (g-C_3N_4) is very limited due to its wide band gap and large contact resistance between layers. To improve the charge separation efficiency and conductivity of g-C_3N_4, a simple covalent modification of fullerene C_ (60) has been developed. The g-C_3N_4/C_ (60) hybrid material covalently bonded with g-C_3N_4 and C_ (60) was synthesized by high energy ball milling. The formation of g-C_3N_4/C_ (60) hybrid structure was confirmed by a series of spectral characterization, and a possible configuration of g-C_3N_4/C_ (60) hybrid material was proposed. Leene C_ (60) is connected to the edge of g-C_3N_4. Then g-C_3N_4/C_ (60) hybrid material is applied to decompose water to produce hydrogen under visible light (lambda 420 nm). Without any precious metal cocatalyst including Pt, the hydrogen production rate of 266 micromol h-1g-1 is obtained, which is higher than that of unmodified g-C_3N_4 (67 micromol h-1g-1). The photocatalytic activity of g-C_3N_4 was enhanced by C_ (60) covalent modification because C_ (60) covalent bonding reduced the conduction band of g-C_3N_4, facilitated the transfer of electrons from photosensitizer to g-C_3N_4, and the rapid transfer of photogenerated electrons from g-C_3N_4 to C_ (60) effectively prevented the recombination of photogenerated electron-hole pairs.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TM914.4
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