Described herein is a series of azafluorene ornamented thiazine based novel fused heterocyclic organic dyes TBCPCA-1, TBCPCA-2, TBTCPCA-1 and TBTCPCA-2. Nanocrystalline titania based DSSC performance along with photophysical/electrochemical behaviors of the aforementioned dyes have been examined. Utilizing computational approach, distribution of electrons within the molecules has been explored. The devices possessing the novel fused dyes TBCPCA-1, TBCPCA-2, TBTCPCA-1 and TBTCPCA-2 as sensitizers exhibited overall power conversion efficiency range between 6.17 +/- 0.4 and 7.97 +/- 0.3%. The novel fused heterocyclic organic dyes featuring di-tert-butylazafluorene structural motif such as TBCPCA-1 and TBCPCA-2 exhibit higher power conversion efficiency than the ones carrying sterically congested tetra-tert-butyl-tri(azafluorene) scaffold viz., TBTCPCA-1 and TBTCPCA-2. Amongst the devices fabricated with the utilization of novel heterocyclic dyes as sensitizers, the device possessing the dye TBCPCA-2 as sensitizer displayed the highest power conversion efficiency of 7.97 +/- 0.3% along with a V-oc of 745 +/- 0.6 mV, a J(sc) of 16.92 +/- 0.3 mA.cm(-2) and a ff of 0.67 +/- 0.003. (C) 2017 Elsevier Ltd. All rights reserved.