We have devised new porphyrin dye Y1A1 for photovoltaic application under both light sources of AM1.5G standard condition and low light intensity at 300 ~ 2400 lux. The dye Y1A1 tailored with two 3,5-di-tert-butyl-4-methoxyphenyl groups at meso-10,20-positions which helps the solubility of the molecule in solvents and avoids involvement of the hazardous chemical n-butyllithium during the synthesis of some typical high efficiency porphyrins such as YD2-o-C8 and LD-series dyes. The dye is also structurally simple so that large-scale synthesis for future industrial application becomes feasible. The Y1A1-based cells were found to exhibit higher performance using I -/I 3 rather than Co 2+/3+ electrolyte in the presence of CDCA co-adsorbent. Addition of Li + together with removal of GuSCN as electrolyte additives benefit the performance in terms of higher capacitance at compensate of surface charge recombination and electron lifetime. The optimized cells based on Y1A1 showed a power conversion efficiency of 9.22% at AM1.5G condition and as high as 19.5%illuminated under 350 lux of LED light. IntroductionSolar cells are well-known technologies in terms of converting energy from sun to a flow of electrons. To provide a controllable and comparable testing condition for solar cells, standard 1 Sun condition (100 mW cm -2 ) is generally equipped in the laboratory for mimicking the outdoor environments which typically shed lights with intensity of >100,000 lux. In contrast, indoor lights surrounding the living places of the community can be considered as low light or dim light due to relatively lower photon flux. These places including homes, schools, offices, factories, hospitals and stores require brightness of light sources typically ranging between 300~500 lux. Higher light level demand for specific area such as laboratories, reading rooms, production halls, first aids and show rooms require the illuminated light of 500~1500 lux. With the thriving concept of indoor energy-harvesting aiming at these reachable light sources, dye-sensitized solar cells (DSCs) are certainly one of the most promising light-to-electricity conversion technologies. 1 DSCs have drawn growing attention since the pioneer work initiated by Grätzel's groups. 2 In the past two decades, molecular engineering of dyes yields several kinds of molecular architectures for efficient solar-to-electricity conversion. 3, 4 These high performance dyes includes the ruthenium polypyridyl complexes, 5, 6 the arylamine-based organic dyes 7-12 and the porphyrin-based dyes. 13-15 Graphical AbstractA new porphyrin dye Y1A1 has been devised for high performance dye-sensitized solar cells under the irradiance of either AM1.5G simulated sunlight or fluorescent/LED based dim light.

A series of simple metal-free organic dyes MS1-MS3 have been designed and synthesized, and their optical, electrochemical, and photovoltaic properties were investigated. The molecular structures are based on a push-pull framework with a triphenylamine, naphthyldiphenylamine, or anthracenyl diphenylamine as the donor connected to a carboxyphenyl acceptor via a C^C bond. The speciality of this new dye design is to obtain higher device open-circuit potentials.The dye-sensitized solar cells using this new sensitizer in combination with I À /I 3 À exhibited exceptionally high V OC values of 810, 844, and 866 mV for MS1, MS2, and MS3, respectively. The absorption bands of the anthracene-bridged dye MS3 showed remarkable peak broadening and red shifts due to the strong electronic coupling between the donor and bridge facilitated by the C-C triple bond, significantly promoting the light-harvesting capability. The resulting devices of MS3 showed large IPCE values of 75-80% in the region 370-590 nm, giving J SC /mA cm À2 ¼ 8.16, V OC /mV ¼ 866, FF ¼ 0.76, and h ¼ 5.44% under standard AM 1.5G one sun irradiation.