Comparative analysis of phenothiazine and phenoxazine sensitizers for dye-sensitized solar cells

•Two acridine dye molecules PTZ-2 and POZ-2 based on "S" and "O" were comparatively analyzed from the atomic level..•The η of POZ-2 is 6.4% which is higher than PTZ-2 (η = 4.9%).•POZ as an electron-donor structural unit was more advantageous than PTZ. Herein, a comparative analysis was carried out to investigate the relationship between performance and structures of PTZ-2 and POZ-2 which based on the units of phenothiazine (PTZ) and phenoxazine (POZ) respectively. The spectral analysis shows that the maximum absorption peaks of these two dyes are 438 nm (PTZ-2) and 465 nm (POZ-2). Electrochemical analysis demonstrate that the better light-harvesting performance of POZ-2 dye is due to its narrow E0–0 (zero–zero transition Energy). Further photovoltaic measurement results show that the η of POZ-2 is 6.4% (Voc=0.727 V, Jsc=12.58 mA cm−2) which is higher than that of PTZ-2 (η=4.9%, Voc=0.722 V; Jsc=9.06 mA cm−2). Finally, the theoretical calculations show that the CSC bond angle (98°) in PTZ-2 is significantly smaller than the COC bond angle (116°) in POZ-2 which attribute to the larger atom radius of "S" than "O". Therefore, a more obvious folding deformation was created in the structure of PTZ-2. That was the main cause of the difference performance between these two dyes.