染料敏化太阳电池中TiO_2颗粒界面接触对电子输运影响的研究

Effect of interface contacts between TiO_2 particles on electron transport in dye-sensitized solar cells

采用溶胶-凝胶法制备TiO2浆料,通过丝网印刷技术印刷和不同温度曲线烧结TiO2薄膜,并应用于染料敏化太阳电池(DSC).高分辨透射电子显微镜发现,低温下多孔薄膜中TiO2颗粒之间呈现点接触,510℃烧结后TiO2颗粒间由点接触变为面接触,近邻颗粒数增多,接触面积增大.同时采用强度调制光电流谱(IMPS)和强度调制光电压谱(IMVS)技术,研究了不同颗粒接触方式和接触面积对电子传输与复合的影响.结果表明:在420—510℃之间,随着烧结温度提高,颗粒接触面积增大,电子传输时间(τd)缩短,电子有效扩散长度(Ln)增大,暗电流减小;当烧结温度达到550℃时,薄膜比表面积减小,多孔结构坍塌,表面态密度增大,电子传输时间(τd)增大.电池光伏特性研究表明:在480—510℃范围内烧结得到的TiO2薄膜,电池短路电流密度(Jsc)最佳,电池效率(η)最好.

Based on sol-gel and screen-printed method,nanoporous TiO2 thin films obtained under different sintering temperatures and times are adopted in dye-sensitized solar cells.According to FESEM,TiO2 particles tend to compact through touch contact under low sintering temperature,but touch contact is substituted by surface contact when the temperature is up to 510℃,which results in larger particle coordination number.Moreover,the influence of different contact ways between TiO2 particles on the electron transport is investigated by IMPS/IMVS technology.The results indicate that with the sintering temperature increasing from 420℃ to 510℃,the electron transport time （τd） decreases while the electron effective diffusion length （Ln） increases,owing to the increased contact surface between TiO2 particles.However,when the sintering temperature increases up to 550℃,the porous structure of the TiO2 electrode collapses and new surface state appears on the TiO2 surface,leading to the increase of τd.It is suggested that the larger short-circuit current density （Jsc） and efficiency （η） can be obtained when the sintering temperature of nanoporous TiO2 film is in a range of 480—510℃.