染料敏化太阳电池中TiO2颗粒界面接触对电子输运影响的研究

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(τ _d)缩短,电子有效扩散长度(L _n)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(τ _d)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(J_sc)最佳,电池效率(η)最好. 关键词： 界面接触 电子输运 暗电流 染料敏化太阳电池

Effect of interface contacts between TiO2 particles on electron transport in dye-sensitized solar cells

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 (τ _d) decreases while the electron effective diffusion length (L _n) 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 τ _d. It is suggested that the larger short-circuit current density (J_sc) and efficiency (η) can be obtained when the sintering temperature of nanoporous TiO₂ film is in a range of 480-510 ℃.