锂掺杂二氧化钛致密层对染料敏化太阳电池性能的影响

Effect of Li-doped TiO_2 Compact Layers for Dye Sensitized Solar Cells

利用脉冲激光沉积(PLD),在纳米多孔二氧化钛层(np-TiO2)与透明导电玻璃之间分别沉积了二氧化钛致密层(d-TiO2)和掺锂二氧化钛致密层(d-Li-TiO2),XRD衍射结果显示该致密层具有锐钛矿结构.电池开路电压随时间的衰减实验结果表明,该结构可以有效减慢开路电压的衰减,抑制透明导电玻璃上的电子向电解质逆向传输并进行电子复合的几率;同时,掺入锂后,致密TiO2层(d-TiO2)能带宽度变窄,降低了np-TiO2层与透明导电玻璃之间的界面电阻,使得np-TiO2层导带上的光生电子更容易地向透明导电玻璃传输,进而使得具有d-Li-TiO2层的染料敏化太阳电池比无致密层的染料敏化太阳电池光电转换效率提高了42%.

Both TiO2 compact layer（d-TiO2） and Li-doped TiO2 compact layer（d-Li-TiO2） were deposited between nano-TiO2 and transparent conductive oxide（TCO） for dye sensitized solar cells（DSSC） by the technique of pulsed laser deposition（PLD）.XRD pattern shows the compact layers are crystallized in anatase structure.Compared with FTO-based DSSC without compact layer,the open voltage decay measurement shows the novel structure can slow the decay of the open circuit voltage,indicating an effective suppression of back electrons transfer from TCO to the electrolyte by the dense buffer layers.In addition,the interface resistance between the nano-TiO2 and the TCO falls down due to the reduced energy band-gap of Li-doped TiO2,which makes it easier to transfer the generated elec-trons from conducting band of nano-TiO2 to TCO surface,leading an enlarged short current from 4.2 mA/cm^2 of FTO-based to 4.8 mA/cm^2 for that with d-TiO2 and 6.1 mA/cm^2 for d-Li-TiO2,respectively.Thus,the photo-voltaic energy conversion efficiency of DSSC based on the Li-doped TiO2 compact layer enhances as much as 42% compared with that FTO-based DSSC without TiO2 compact layer.