The YL4 dye exhibits DSSC efficiencies of 10.87% (1 sun) and 27.54% (187 lux) due to effective double layered shelters (the dianchor skeleton and clogged TPE units) for blockade of dark current.

DSSCs fabricated from benzo[3,4-b]pyrazine-based metal-free sensitizers have efficiencies of 9.03% under 1 sun and 18.95% under 300 lux irradiance.

A simple and effective modifi cation of phenyl-C 70 -butyric acid methyl ester (PC 70 BM) is carried out in a single step after which the material is used as electron acceptor for bulk heterojunction polymer solar cells (PSCs). The modifi ed PC 70 BM, namely CN-PC 70 BM, showed broader and stronger absorption in the visible region (350-550 nm) of the solar spectrum than PC 70 BM because of the presence of a cyanovinylene 4-nitrophenyl segment. The lowest unoccupied molecular energy level (LUMO) of CN-PC 70 BM is higher than that of PC 70 BM by 0.15 eV. The PSC based on the blend (cast from tetrahydrofuran (THF) solution) consists of P3HT as the electron donor and CN-PC 70 BM as the electron acceptor and shows a power conversion effi ciency (PCE) of 4.88%, which is higher than that of devices based on PC 70 BM as the electron acceptor (3.23%). The higher PCE of the solar cell based on P3HT:CN-PC 70 BM is related to the increase in both the short circuit current ( J sc ) and the open circuit voltage ( V oc ). The increase in J sc is related to the stronger light absorption of CN-PC 70 BM in the visible region of the solar spectrum as compared to that of PC 70 BM. In other words, more excitons are generated in the bulk heterojunction (BHJ) active layer. On the other hand, the higher difference between the LUMO of CN-PC 70 BM and the HOMO of P3HT causes an enhancement in the V oc . The addition of 2% (v/v) 1-chloronapthalene (CN) to the THF solvent during fi lm deposition results in an overall improvement of the PCE up to 5.83%. This improvement in PCE can be attributed to the enhanced crystallinity of the blend (particularly of P3HT) and more balanced charge transport in the device.

Three new hole-transporting materials (HTMs), composed of N 3 ,N 6bis(di-4-anisylamino)-9H-carbazole and anthracene moieties, have been developed for perovskite solar cell (PSC) application. Two of the new HTMs have better hole mobility and hole-extraction ability compared to spiro-OMeTAD. Accordingly, the best PSC based on mixed ion perovskite of Cs 0.05 FA 0.79 MA 0.16 PbI 2.49 Br 0.51 and doped HTMs has better power conversion efficiency (18.65%) than the corresponding PSC based on doped spiro-OMeTAD (17.90%). Moreover, the PSCs based on these HTMs have negligible hysteresis and good temporal stability.

Cost-effective imidazole-based star-shaped arylamines were used as dopant-free hole transport materials (HTMs) for high performance perovskite solar cells (17.47%).

A series of five new ruthenium [3 + 2 + 1] complexes coded as MC107-MC111, with novel unsymmetrical bipyridines as ancillary ligands and terpyridine tricarboxylic acid as an anchoring ligand have been successfully synthesized and characterized by 1 H NMR, 13 C NMR and UV-Visible spectrometry.Improvement in the molar extinction coefficient of all these sensitizers was observed compared with reference standard N749 dye under comparable conditions. Among all the new sensitizers MC108 exhibited a maximum solar to electrical conversion efficiency of 5.573% (J sc ¼ 16.81 mA cm À2 , V oc ¼ 0.50 V. FF ¼ 0.65) under standard global AM 1.5 G solar condition, when compared to the N749 dye with an efficiency of 6.29% (J sc ¼ 13.74 mA cm À2 , V oc ¼ 0.67 V. FF ¼ 0.68) under similar fabrication and evaluation conditions. Density functional theory (DFT) and time-dependent DFT calculations are carried out for MC107-MC111 to understand their structural, electronic and photophysical properties.

The photovoltaic performance of the polymer bulk heterojunction solar cells based on the low-band-gap D− A copolymer P as donor and modified fullerene (modi-PC 60 BM) as acceptor was in. We have achieved power conversion efficiency (PCE) of ∼2.35% for a polymer solar cell with modi-PC 60 BM as an electron acceptor in bulk heterojunction active layer, which is higher than that for PC 60 BM counterpart (1.50%). The increase in the PCE has been attributed to the increase in absorption in visible and higher LUMO level of modi-PC 60 BM, resulting in enhancement in J sc and V oc , respectively. In the device fabrications, we studied the effect of the solvent additive and modified PEDOT:PSS as a hole transport layer. The PCE of the polymer solar cell was improved up to 3.63% when the P:modi-PC 60 BM active layer was processed with the addition of CN as an additive in the THF solution (CN/THF), which is mainly attributed to more balanced charge transport due to the increased crystallinity of P in the blend. The PCE of polymer solar cell based on the active layer processed from CN/THF has been further improved up to 4.73% when a modified PEDOT:PSS (acetone-treated) was used as the hole transport layer. This increase in the PCE is mainly due to the enhancement in J sc and FF and may be attributed to the improvement in the conductivity induced by the polar solvent with high dipole moment, leading to more efficient collection of charge carrier by the anode.

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