The photoanode of a dye-sensitized solar cell (DSSC), usually made with a nanoporous TiO₂ semiconductor layer sensitized with N719 dye, plays a crucial role in the overall power conversion efficiency as it influences both the light absorption and the electron transport. Generally, enhanced photon absorbance is achieved through light scattering in the device by employing a double-layered TiO₂ photoanode consisting of an active layer of smaller (~ 20 nm) P25 particles and a scattering layer consisting of larger (~ 300 nm) particles. However, due to the smaller effective surface area of the larger particle layer, the dye adsorption in the second layer is very poor, and therefore, the efficiency enhancement due to the usage of thicker photo anode is hindered. Therefore, in this study, investigations were carried out to replace the conventional, larger particle scattering layer by a morphologically different structure of TiO₂. Here, the DSSC performance between two different types of scattering layers, one consisting of TiO₂ nanorods (NRs) and the other consisting of hierarchically structured TiO₂ submicron size spheres (MS) are compared. DSSC fabricated with P25/MS double-layered photoanode outperforms the DSSC fabricated with P25/NR double-layered photoanode. P25/MS-based DSSC delivered a highest short-circuit current density of 14.80 mA cm⁻² with an efficiency of 7.38%, while the efficiency of DSSC fabricated with P25/NR photoanode exhibits 7.03% efficiency. The DSSC fabricated without a scattering layer showed only 6.68% efficiency. The diffuse reflectance and dye adsorption measurements revealed that the better performance of P25/MS double-layered DSSC is largely due to the improved photon absorption facilitated by superior light scattering as well as higher dye loading by TiO₂ submicron size spheres.

Graphical abstract

染料敏化太阳能电池（DSSC）的光阳极通常由N719染料敏化的纳米多孔TiO ₂半导体层制成，它在总体功率转换效率中起着至关重要的作用，因为它会影响光吸收和电子传输。通常，通过使用双层TiO ₂可以通过器件中的光散射来提高光子吸收率由较小（〜20 nm）P25颗粒的活性层和由较大（〜300 nm）颗粒组成的散射层组成的光电阳极。然而，由于较大颗粒层的有效表面积较小，第二层中的染料吸附非常差，因此，由于使用较厚的光阳极而导致的效率提高受到阻碍。因此，在这项研究中，进行了研究以用形态不同的TiO ₂代替常规的较大的颗粒散射层。在此，两种不同类型的散射层之间的DSSC性能，一种是由TiO ₂纳米棒（NRs）组成，另一种是由分层结构的TiO ₂组成。比较了亚微米尺寸球（MS）。用P25 / MS双层光电阳极制造的DSSC优于用P25 / NR双层光电阳极制造的DSSC。基于P25 / MS的DSSC的最高短路电流密度为14.80 mA cm ^-2，效率为7.38％，而使用P25 / NR光电阳极制造的DSSC的效率为7.03％。没有散​​射层制造的DSSC仅显示6.68％的效率。漫反射率和染料吸附测量结果表明，P25 / MS双层DSSC的更好性能很大程度上归因于优异的光散射以及TiO ₂亚微米尺寸的球体带来的更高的染料载量，从而改善了光子吸收。

图形概要