Indoor utilization of emerging photovoltaics is promising; however, efficiency characterization under room lighting is challenging. We report the first round-robin interlaboratory study of performance measurement for dye-sensitized photovoltaics (cells and mini-modules) and one silicon solar cell under a fluorescent dim light. Among 15 research groups, the relative deviation in power conversion efficiency (PCE) of the samples reaches an unprecedented 152%. On the basis of the comprehensive results, the gap between photometry and radiometry measurements and the response of devices to the dim illumination are identified as critical obstacles to the correct PCE. Therefore, we use an illuminometer as a prime standard with a spectroradiometer to quantify the intensity of indoor lighting and adopt the reverse-biased current-voltage (I-V) characteristics as an indicator to qualify the I-V sampling time for dye-sensitized photovoltaics. The recommendations can brighten the prospects of emerging photovoltaics for indoor applications.

A series of organic dyes containing oligo-phenothiazine were synthesized and used effectively on the fabrication of dye-sensitized solar cells (DSSCs). In these compounds the phenothiazine moiety functions both as an electron donor and as a p-bridge. These materials exhibit considerably high values of open-circuit voltage (V oc ) ranging from 0.78-0.83 V under an AM1.5 solar condition (100 mW cm À2 ). Two kinds of substituents, i.e., hexyl and hexyloxyphenyl groups, were added onto the N(10) of phenothiazine for comparison. The best device displayed a short-circuit current (J sc ) of 14.3 mA cm À2 , an open-circuit voltage (V oc ) of 0.83 V, a fill factor (FF) of 0.65, corresponding to an overall conversion efficiency of 7.78%. Their photophysical properties were analyzed with the aid of a time-dependent density functional theory (TDDFT) model with the B3LYP functional. The electronic nature of the devices was further elucidated by using electrochemical impedance spectroscopy.

A new class of hole-transport materials (HTMs) based on the bimesitylene core designed for mesoporous perovskite solar cells is introduced. Devices fabricated using two of these derivatives yield higher open-circuit voltage values than the commonly used spiro-OMeTAD. Power conversion efficiency (PCE) values of up to 12.11% are obtained in perovskite-based devices using these new HTMs. The stability of the device made using the highest performing HTM (P1) is improved compared with spiro-OMeTAD as evidenced through long-term stability tests over 1000 h.

Organic dyes consisting of a [2.2]paracyclophane unit along the main chromophore are examined for their application in sensitized solar cells. These materials exhibit considerably high values of open-circuit voltage (V(oc)) ranging 0.69-0.72 V, and an overall efficiency up to 3.8%.

No abstract

A series of new pyridomethene-BF2/phenothiazine-hybrid metal-free organic sensitizers K1-K8 containing different πspacers were synthesized and applied in dye-sensitized solar cells (DSSC). The introduction of the pyridomethene-BF2 complex unit to the phenothiazine chromophore displayed a high molar extinction coefficient in favor of light-harvesting. Quantum chemical calculations were performed by using the density functional theory (DFT) at the B3LYP/6-31G (d,p) level to investigate the structural properties and electron density distributions of these dyes. The effect of dyes K1-K8 on the performance of DSSC was investigated systematically with comparisons to the plane phenothiazine dyes R1 and R2. Upon co-adsorption with deoxycholic acid, the dye K3 with a thiophene unit between the phenothiazine and pyridomethene-BF2 units exhibited the best photovoltaic performance. The short-circuit current density (Jsc) was 15.43 mA cm -2 with an open-circuit voltage (Voc) 0.69 V and a fill factor (FF) 0.62, that corresponded to a power-conversion efficiency (η) 6.58% under AM 1.5G irradiation (100 mW．cm -2 ) condition. The n-hexyl chain attached to the thiophene in K4-K5 exhibitted an effect of improving the Voc value. The presence of the phenyl pyridomethene-BF2 moiety at the N(10) atom of phenothiazine in K6-K8 showed a good effect of reducing π-π aggregation. These results revealed the advantage of incorporating a pyridomethene-BF2 group in the dyes for high performance DSSC cells.

No abstract

A series of organic dyes were prepared that displayed remarkable solar-to-energy conversion efficiencies in dye-sensitized solar cells (DSSCs). These dyes are composed of a 4-tert-butylphenylamine donor group (D), a cyanoacrylic-acid acceptor group (A), and a phenylene-thiophene-phenylene (PSP) spacer group, forming a D-π-A system. A dye containing a bulky tert-butylphenylene-substituted carbazole (CB) donor group showed the highest performance, with an overall conversion efficiency of 6.70%. The performance of the device was correlated to the structural features of the donor groups; that is, the presence of a tert-butyl group can not only enhance the electron-donating ability of the donor, but can also suppress intermolecular aggregation. A typical device made with the CB-PSP dye afforded a maximum photon-to-current conversion efficiency (IPCE) of 80% in the region 400-480 nm, a short-circuit photocurrent density J(sc) =14.63 mA cm(-2), an open-circuit photovoltage V(oc) =0.685 V, and a fill factor FF=0.67. When chenodeoxycholic acid (CDCA) was used as a co-absorbent, the open-circuit voltage of CB-PSP was elevated significantly, yet the overall performance decreased by 16-18%. This result indicated that the presence of 4-tert-butylphenyl substituents can effectively inhibit self-aggregation, even without CDCA.