Strong Metal-support Interaction Enables Highly Transparent Pt-Mo₂C Electrodes For Bifacial Dye-sensitized Solar Cells

DSCs have attracted enormous attentions due to their multi-color appearance and satisfactory power output under insufficient illuminant.Bifacial DSCs can increase the photoelectric conversion efficiency?PCE?by 30%-50%because they can utilize photons from different direction.The key to improve the"cost-effectiveness"of bifacial DSCs is to improve the PCE irradiated from rear side,however,the unsatisfactory transparence of CEs seriously limits the rear efficiency of bifacial DSCs CEs work based on the electrocatalytic principle.Nowadays,the reported strategy to increase transparence of DSCs is usually reducing the amount of light-absorbing electrocatalytic materials,which would cause the insufficient number of catalytic sites and restrict the catalytic activity of the transparent CEs.To solve this problem,we propose a strategy based on the strong interaction of between Pt and support to achieve the co-improvement of the light transmittance and catalytic activity.The specific researches are as follows:?1?We fabricated of Pt-Mo₂C CEs based on the strong interaction between Pt and support to achieve the co-improvement of optical transmittance and catalytic activity.The Mo₂C support were loaded by Pt catalyst through the immersing process and high-temperature annealing treatment after.Pt-Mo₂C exhibited ultra-high optical transmittance in the visible light region,the transmittance of which is only induced by 3% at550 nm compared to that of conductive glass?FTO?.There is a strong electron transfer interaction between Pt and Mo₂C proved by the XPS measurements,which is the essential origin of smaller size and better dispersity of Pt clusters on the Mo₂C support than those on the W₂C and FTO support.Consequently,The DSCs with Pt-Mo₂C CE exhibited front PCE of 7.5%and rear PCE of 5.6%.The transparent Pt-Mo₂C CE successfully maintained 75% of front PCE.In contrast,the rear PCE of HT-Pt cells is only 56% of the front one.?2?We further enhanced the interaction between Pt and Mo₂C through surface-modification of Mo₂C.The surface-modified of Mo₂C was achieved by O₂ plasma treatment under different conditions.Pt-P?Mo₂C?-15s CEs with a low-loading,high catalytic activity and high optical transmission,was obtained by the high-temperature annealing treatment after spin-coating chloroplatinic acid solution onto Mo₂C surface.We carefully investigated the O₂ plasma treatment condition on the performance of CEs to obtain an optimized temperature of 100?,power of 150 W,and time of 15 s.The transmittance at 550nm of optimized Pt-P?Mo₂C?-15s CEs is only induced by 2.81%.In addition,Pt-P?Mo₂C?-15s showed the excellent catalytic activity processing.It can be seen that the Pt/Mo ratio in Pt-P?Mo₂C?-15s is reduced by 0.5%compared with un treated Pt-Mo₂C CEs according to the XPS element content analysis Besides,the binding energy of Pt 4f up-shifted by 0.16 eV compared with untreated sample,which proves that there is a stronger electron transfer interaction between Pt and the support after the O₂ plasma treatment.The DSCs with Pt-Mo₂C CE exhibited higher efficiency retention PCE of 77%.