Dim Light Conditions Research Articles

Tandem dye-sensitized solar cells with efficiencies surpassing 33% under dim-light conditions

To fabricate dye-sensitized solar cells (DSSCs), the variation of TiO2 film thickness elicits contrary effects on the light-harvesting and charge transfer, thereby affecting cell performance. To compromise the TiO2 thickness on the two effects, tandem DSSCs constructed by stacking two cells in series were proposed herein. Cells with high transparent photoelectrodes and counter electrodes were employed as the top cells; thus, the light unabsorbed by the top cells can be transmitted through, and harvested by the bottom cells. Furthermore, cobalt redox couple was adopted to decrease the light loss caused by absorption of the electrolyte. By regulating the film thicknesses of the top and bottom cells, both light harvest and charge transfer performance can be improved simultaneously, thereby, achieving a conversion efficiency as high as 33.98% under 2000 lx fluorescent lighting. This efficiency is much higher than the value (26.57%) obtained by the single cell. The tandem structure can also be applied under sunlight conditions, which can increase the efficiency from 9.27% to 11.31%.

0638 Circadian rhythms among youth with craniopharyngioma

Abstract Introduction Craniopharyngioma is an intracranial tumor located in the hypothalamic and pituitary region. Despite high survival rates for youth with craniopharyngioma, quality of life is substantially affected. Morbidity includes high rates of sleep disruption, particularly disorders of hypersomnolence. Circadian rhythms may also be affected due to the proximity of the tumor and subsequent treatment to the hypothalamic-pituitary-adrenal axis, though the role of circadian rhythms has been less studied in this patient population. To evaluate circadian rhythms among youth with craniopharyngioma, dim light melatonin onset (DLMO), an established marker of the circadian system, was estimated. Methods Fifty-five patients between the ages of 7 and 20 years participated in this study. Data were collected prior to completion of proton therapy (if indicated). Participants provided hourly saliva samples, in their homes, starting 3 hours prior to habitual bedtime until 1 hour following in dim light conditions (<30 lux). DLMO was calculated based on a threshold of 4 pg/ml. Participants also wore actigraphs to measure sleep patterns. We derived bedtime and waketime from actigraphy and calculated phase angles to bedtime and waketime. DLMO timing and phase angles were compared to published norms for healthy youth ages 9 to 17 years. Results DLMO could not be estimated for almost half of the sample (n=25), most often due to a melatonin value above the threshold at the first collection time point. Higher grade of hypothalamic involvement and the presence of diabetes insipidus predicted inability to capture DLMO. Subsample analyses of participants with DLMO (n=30) showed later DLMO timing and shorter phase interval to bedtime than the healthy reference sample. Conclusion With standard practice for DLMO estimation, we only obtained estimates for slightly more than half our sample. This may reflect circadian rhythm disturbances or advanced circadian phase. Relative to published norms, those with captured DLMO had later DLMO timing and shorter phase angles to bedtime, indicating sleep at an earlier circadian phase. These findings suggest possible circadian rhythm disruption in pediatric craniopharyngioma. Methodological differences among samples may also contribute to findings. Further examination of circadian rhythm disruption and relations with other sleep disturbances is needed. Support (If Any) This work was supported by the Cancer Center Support Grant (CA21765) from the National Cancer Institute and ALSAC.

Egg rejection based on egg size recognition as a specific strategy against parasitic cuckoos.

In the coevolutionary interactions between avian brood parasites and their hosts, egg recognition based on color and/or pattern is a common and effective defense to counter parasitism. However, for egg recognition based on size, only a few studies have found affirmative results, and they do not provide unambiguous evidence that egg size recognition in hosts has evolved as an important and specific anti-parasite adaptation against parasite eggs. We studied the brood parasite system between the Asian emerald cuckoo Chrysococcyx maculatus and its host, the chestnut-crowned warbler Phylloscopus castaniceps. The cuckoo parasitizes the warbler using non-mimetic and larger eggs at a parasitism rate of 12.9%. The warbler nests used in this experiment were built in a dark environment with the nest illuminance near 0 lux. Experiments with 2 types of model eggs with colors and patterns resembling cuckoo eggs of different sizes (cuckoo egg size or host egg size) showed that the warblers were able to reject 63.6% of cuckoo model eggs under these dim light conditions. However, model eggs with the same color and pattern similar to the warbler egg size were always accepted. This study provides strong evidence supporting the theory that egg size recognition can be evolved in hosts as a specific anti-parasite adaptation against cuckoos. We suggest that the egg size recognition of the warbler is an outcome of the tradeoff between the costs of violating the parental investment rule and suffering cuckoo parasitism.

Bumblebees land rapidly by intermittently accelerating and decelerating toward the surface during visually guided landings

SummaryMany flying animals parse visual information to control their landing, whereby they can decelerate smoothly by flying at a constant radial optic expansion rate. Here, we studied how bumblebees (Bombus terrestris) use optic expansion information to control their landing, by analyzing 10,005 landing maneuvers on vertical platforms with various optic information, and at three dim light conditions. We showed that bumblebees both decelerate and accelerate during these landings. Bumblebees decelerate by flying at a constant optic expansion rate, but they mostly accelerate toward the surface each time they switched to a new, often higher, optic expansion rate set-point. These transient acceleration phases allow bumblebees to increase their approach speed, and thereby land rapidly and robustly, even in dim twilight conditions. This helps explain why bumblebees are such robust foragers in challenging environmental conditions. The here-proposed sensorimotor landing control system can serve as bio-inspiration for landing control in unmanned aerial vehicles.

Functional daylight echolocation in highly visual bats

Bats rely on echolocation for operating in dim light or dark conditions. Accordingly, most research on echolocation is performed under dark conditions with a few exceptions. Bat species that emerge to forage before sunset have been shown to use echolocation even in relatively high light levels1-3. It has been argued that for insectivorous bats, as light levels decrease, echolocation rapidly becomes advantageous over vision for detecting tiny insects during dusk or dawn2 and that information from the two sensory modalities is integrated4,5. Functional use of echolocation in broad daylight in insectivorous bats has been scarcely reported6,7. Here, we report functional use of echolocation in broad daylight in highly visual fruit bats.

Oviposition site selection in the crepuscular moth, Grapholita molesta: does light matter?

AbstractSome insects that particularly prefer sunny or shaded sites use light intensity to locate suitable oviposition sites during the day. However, it is not known whether crepuscular species can be guided by light for oviposition under dim or variable light conditions. We used the crepuscular moth Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a major pest of stone and pome fruits worldwide, to investigate oviposition response to light at various intensities (1000, 100, 10, and 1 mW m−2). Light intensity in sunny sites in a peach tree canopy is about 10× higher than in shaded sites. In both light vs. dark and brighter light vs. darker light choices, G. molesta females can discriminate differences in light intensity, exhibiting a strong preference for brighter light, independent of light intensity. Moreover, the light‐dependent oviposition responses did not change when exposed to odor stimuli. Our findings show that this crepuscular moth G. molesta can use light intensity to direct oviposition toward relatively sunny sites under dim light conditions. This study highlights the importance of vision for crepuscular species in oviposition site selection.

Natural polyelectrolyte-based ultraflexible photoelectric synaptic transistors for hemispherical high-sensitive neuromorphic imaging system

Outstanding features of the human retina are its concave hemispherical geometry, high-sensitive image acquisition, and neuromorphic visual processing, which not only simplifies the optical complexity for the eye but also enhances imaging quality for the visual perception. However, the development of a high-performance bioinspired imaging system with these features is extremely challenging because of the restriction of its composing materials, device structures, and conventional imaging modules. Here, we present a novel hemispherical high-sensitive neuromorphic imaging system that leverages a natural acidic polyelectrolyte as dielectric layer in the photoelectric synaptic transistors. The devices have an extraordinary photosensitivity (~104) under a dim light condition (56 μW/cm2) and the light-tunable neuromorphic characteristics, as well as a substrate-free and ultrathin (~475 nm) structure. These advantages enable our system to perform high-quality imaging like the human retina and highly simulate various functions of the human visual system, such as image enhancement and erasure, and visual preprocessing.

Effects of different light incident angles via a head-mounted device on the magnitude of nocturnal melatonin suppression in healthy young subjects

Bright light is a primary zeitgeber (synchronizer) for the central circadian pacemaker in humans. Recently, head-mounted devices for light therapy have been developed to treat patients suffering from circadian rhythm sleep disorders. In this study, to evaluate the influence of the light incident angle of head-mounted devices on the human circadian pacemaker, we examined the effects of bright light (ca.10000 lx) from two different angles (55° vs. 28°) on the suppression of melatonin secretion at night. Twenty-nine subjects (25.1 ± 6.3 SD years) participated in the present study. The subjects were kept under dim light conditions (< 5 lx) from 4 h before their habitual bedtime, followed by exposure to 1 h of bright light at two different angles during their habitual bedtime. Saliva samples were collected every hour under dim light conditions and then collected every 30 min during the bright light exposure. To assess the effect of the light incident angle on ipRGCs mediating light-evoked pupillary constriction, pupil size was measured in before and after exposure to bright light. Melatonin suppression in the group exposed to light at 28° was significantly higher than that in the group with light at 55° (p < 0.001). The pupillary constriction was significantly greater in the group exposed to light at 28° than that in the group with light at 55° (p < 0.001). The present findings suggest that the light incident angle is an important factor for bright light therapy and should be considered to effectively use head-mounted devices in home and clinical settings.

Light matters: Nest illumination alters egg rejection behavior in a cavity-nesting bird

Egg discrimination by cavity-nesting birds that build nests under dim light conditions was presumed to depend on nest luminance, although this hypothesis has rarely been tested. Tests of egg discrimination ability by cavity-nesting tits under dim light conditions may reveal the selection pressure from brood parasitism that they encounter under natural interactions. We manipulated the intensity of luminance of nests of the Green-backed Tit (Parus monticolus), a potential cuckoo host that possesses a strong discrimination ability of non-mimetic foreign eggs. We performed experiments to test their egg discrimination ability under different light conditions. Our results showed that Green-backed Tits discriminate against non-mimetic foreign eggs under normal light conditions in nest boxes, and this ability persisted at nest luminance as low as 4.78 ​± ​1.31 lux that is several times lower than normal luminance (38.11 ​± ​24.02 lux). However, egg discrimination by Green-backed Tits disappeared when nest luminance was reduced to a minimum of 0.35 ​± ​0.15 lux. The latter value represents total darkness for humans. The present study shows that nest luminance plays a key role in egg discrimination by Green-backed Tits that build nests under dim light conditions. This study provides strong experimental evidence for nest illumination altering egg rejection behavior in cavity-nesting birds.

Tandem Dye-Sensitized Solar Cells with Efficiencies Surpassing 33% Under Dim-Light Conditions

Tandem Dye-Sensitized Solar Cells with Efficiencies Surpassing 33% Under Dim-Light Conditions

Adaptation of Temperate Seagrass to Arctic Light Relies on Seasonal Acclimatization of Carbon Capture and Metabolism.

Due to rising global surface temperatures, Arctic habitats are becoming thermally suitable for temperate species. Whether a temperate species can immigrate into an ice-free Arctic depends on its ability to tolerate extreme seasonal fluctuations in daylength. Thus, understanding adaptations to polar light conditions can improve the realism of models predicting poleward range expansions in response to climate change. Plant adaptations to polar light have rarely been studied and remain unknown in seagrasses. If these ecosystem engineers can migrate polewards, seagrasses will enrich biodiversity, and carbon capture potential in shallow coastal regions of the Arctic. Eelgrass (Zostera marina) is the most widely distributed seagrass in the northern hemisphere. As the only seagrass species growing as far north as 70°N, it is the most likely candidate to first immigrate into an ice-free Arctic. Here, we describe seasonal (and diurnal) changes in photosynthetic characteristics, and in genome-wide gene expression patterns under strong annual fluctuations of daylength. We compared PAM measurements and RNA-seq data between two populations at the longest and shortest day of the year: (1) a Mediterranean population exposed to moderate annual fluctuations of 10–14 h daylength and (2) an Arctic population exposed to high annual fluctuations of 0–24 h daylength. Most of the gene expression specificities of the Arctic population were found in functions of the organelles (chloroplast and mitochondrion). In winter, Arctic eelgrass conserves energy by repressing respiration and reducing photosynthetic energy fluxes. Although light-reactions, and genes involved in carbon capture and carbon storage were upregulated in summer, enzymes involved in CO2 fixation and chlorophyll-synthesis were upregulated in winter, suggesting that winter metabolism relies not only on stored energy resources but also on active use of dim light conditions. Eelgrass is unable to use excessive amounts of light during summer and demonstrates a significant reduction in photosynthetic performance under long daylengths, possibly to prevent photoinhibition constrains. Our study identified key mechanisms that allow eelgrass to survive under Arctic light conditions and paves the way for experimental research to predict whether and up to which latitude eelgrass can potentially migrate polewards in response to climate change.

Multimodal Approach towards Large Area Fully Semitransparent Perovskite Solar Module

AbstractSignificant advancements in the perovskite solar cells/modules (PSCs/PSMs) toward better operational stability and large area scalability have recently been reported. However, semitransparent (ST), high efficiency, and large area PSMs are still not well explored and require attention to realize their application in building‐integrated photovoltaics (BIPV). This work employs multiple synergistic strategies to improve the quality and stability of the ST perovskite film while ensuring high transparency. Europium ions, doped in the perovskite, are found to suppress the generation of detrimental species like elemental Pb and I, resulting in higher atmospheric stability. The effect of the top transparent contact is designed to obtain an average visible transparency (AVT) of &gt;20% for full device and a green colored hue. Lastly, the lower current density due to the thinner ST absorber is enhanced by the application of a down‐converting phosphor material which harvests low energy photons and inhibits UV‐induced degradation. This multimodal approach renders a power conversion efficiency of 12% under dim light conditions and 9.5% under 1 sun illumination, respectively, on 21 cm2 ST‐PSM.

A novel exome probe set captures phototransduction genes across birds (Aves) enabling efficient analysis of vision evolution.

The diversity of avian visual phenotypes provides a framework for studying mechanisms of trait diversification generally, and the evolution of vertebrate vision, specifically. Previous research has focused on opsins, but to fully understand visual adaptation, we must study the complete phototransduction cascade (PTC). Here, we developed a probe set that captures exonic regions of 46 genes representing the PTC and other light responses. For a subset of species, we directly compared gene capture between our probe set and low-coverage whole genome sequencing (WGS), and we discuss considerations for choosing between these methods. Finally, we developed a unique strategy to avoid chimeric assembly by using "decoy" reference sequences. We successfully captured an average of 64% of our targeted exome in 46 species across 14 orders using the probe set and had similar recovery using the WGS data. Compared to WGS or transcriptomes, our probe set: (1) reduces sequencing requirements by efficiently capturing vision genes, (2) employs a simpler bioinformatic pipeline by limiting required assembly and negating annotation, and (3) eliminates the need for fresh tissues, enabling researchers to leverage existing museum collections. We then utilized our vision exome data to identify positively selected genes in two evolutionary scenarios-evolution of night vision in nocturnal birds and evolution of high-speed vision specific to manakins (Pipridae). We found parallel positive selection of SLC24A1 in both scenarios, implicating the alteration of rod response kinetics, which could improve color discrimination in dim light conditions and/or facilitate higher temporal resolution.

O031 Nocturnal melatonin secretion in post-treatment breast cancer patients: a preliminary study

Abstract Purpose Breast-cancer patients frequently report of poor sleep-quality. Although the pathophysiology is unclear, circadian-sleep misalignment is a plausible mechanism. We compared nocturnal melatonin-secretion, a circadian rhythm marker, in post-menopausal, post-treatment (≥12-months) female breast-cancer patients (BCG), with post-menopausal female controls with no history of cancer (CG) Methods We recruited 6 BCG and 10 CG from Westmead Hospital breast-cancer outpatient clinic or hospital-staff community, respectively. Participants completed the Pittsburgh Sleep Quality Index (PSQI; &amp;gt;5 PSQI-score=poor sleep-quality) and ~7 days of home-actigraphy (Philips Actiwatch-2, Philips Respironics, USA) to ascertain habitual bed-time (HBT). Later, participants completed an overnight, in-laboratory study, with saliva sampled (n=13) at regular intervals under strict dim-light conditions (&amp;lt;1 lux). Salivary-melatonin concentrations were quantified via radioimmunoassay (University of Adelaide). We measured 1) clock-time when salivary-melatonin concentrations reached 4pg/mL (melatonin onset-[DLMO-4pg/ml]) and 2) time-interval between HBT and DLMO-4pg/ml (indicates circadian-sleep misalignment-[PAR-DLMO]). Data were expressed as median [interquartile range], and compared using 2-sided Mann Whitney U-tests. p&amp;lt;0.05 was considered significant. Results BCG and CG had similar ages (62.5 [59.5–67.3] vs. 58.5 [54.0–66.3] yrs, respectively; p=0.23). Compared with CG, BCG had higher PSQI-scores (8.50 [5.25–10.75] vs. 4.00 [3.75–5.50] a.u.; p=0.07), but similar HBT (22:49 [21:46-23:38] vs. 22:17 [21:59-22:21] h:min; p=0.26). BCG had later DLMO-4pg/ml (20:46 [20:01-22:03] vs. 18:23 [17:55-20:07] h:min; p=0.03) and shorter PAR-DLMO (1.43 [0.96–2.38] vs. 3.63 [2.18–3.90] hrs; p=0.09), than CG. Conclusion Preliminary data indicate BCG had poorer sleep-quality, delayed melatonin onset, and altered circadian-sleep alignment; compared with CG. We speculate disrupted nocturnal melatonin-secretion potentially influences poor sleep-quality reported by breast-cancer patients.

If You’re Happy and You Know it Stay Alert: The Effects of Lighting on Vigilance Performance and Affective State

Vigilance, or sustained attention tasks involve detecting critical signals, embedded amid more frequent neutral signals, over an extended period of time. A decline in performance, engagement, and arousal over time, as well as high workload and stress, are common outcomes of such tasks. Exposure to broad-spectrum or short wavelength bright light has been found to positively impact alertness, speed of information processing, and mood, but has not been extensively explored in the vigilance domain. The present study explored whether a light therapy lamp could mitigate the negative vigilance outcomes found in both performance and affective state. Results indicated that the therapy light did not prevent a decline in detection of critical signals over time, nor significantly impact workload, sleepiness, or subjective stress state compared to a dim light condition. However, mood questionnaire results suggest that lighting may impact separate constructs of arousal and tiredness, warranting further research.

Mitochondrial Retinopathy

To report the retinal phenotype and the associated genetic and systemic findings in patients with mitochondrial disease. Retrospective case series. Twenty-three patients with retinopathy and mitochondrial disease, including chronic progressive external ophthalmoplegia (CPEO), maternally inherited diabetes and deafness (MIDD), mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), Kearns-Sayre syndrome, neuropathy, ataxia, and retinitis pigmentosa (NARP) syndrome, and other systemic manifestations. Review of case notes, retinal imaging, electrophysiologic assessment, molecular genetic testing including protein modeling, and histologic analysis of muscle biopsy. Phenotypic characteristics of mitochondrial retinopathy. Genetic testing identified sporadic large-scale mitochondrial DNA deletions and variants in MT-TL1, MT-ATP6, MT-TK, MT-RNR1, or RRM2B. Based on retinal imaging, 3 phenotypes could be differentiated: type 1 with mild, focal pigmentary abnormalities; type 2 characterized by multifocal white-yellowish subretinal deposits and pigment changes limited to the posterior pole; and type 3 with widespread granular pigment alterations. Advanced type 2 and 3 retinopathy presented with chorioretinal atrophy that typically started in the peripapillary and paracentral areas with foveal sparing. Two patients exhibited a different phenotype: 1 revealed an occult retinopathy, and the patient with RRM2B-associated retinopathy showed no foveal sparing, no severe peripapillary involvement, and substantial photoreceptor atrophy before loss of the retinal pigment epithelium. Two patients with type 1 disease showed additional characteristics of mild macular telangiectasia type 2. Patients with type 1 and mild type 2 or 3 disease demonstrated good visual acuity and no symptoms associated with the retinopathy. In contrast, patients with advanced type 2 or 3 disease often reported vision problems in dim light conditions, reduced visual acuity, or both. Short-wavelength autofluorescence usually revealed a distinct pattern, and near-infrared autofluorescence may be severely reduced in type 3 disease. The retinal phenotype was key to suspecting mitochondrial disease in 11 patients, whereas 12 patients were diagnosed before retinal examination. Different types of mitochondrial retinopathy show characteristic features. Even in absence of visual symptoms, their recognition may facilitate the often challenging and delayed diagnosis of mitochondrial disease, in particular in patients with mild or nebulous multisystem disease.

The interindividual variability of sleep timing and circadian phase in humans is influenced by daytime and evening light conditions

Human cognitive functioning shows circadian variations throughout the day. However, individuals largely differ in their timing during the day of when they are more capable of performing specific tasks and when they prefer to sleep. These interindividual differences in preferred temporal organization of sleep and daytime activities define the chronotype. Since a late chronotype is associated with adverse mental and physical consequences, it is of vital importance to study how lighting environments affect chronotype. Here, we use a mathematical model of the human circadian pacemaker to understand how light in the built environment changes the chronotype distribution in the population. In line with experimental findings, we show that when individuals spend their days in relatively dim light conditions, this not only results in a later phase of their biological clock but also increases interindividual differences in circadian phase angle of entrainment and preferred sleep timing. Increasing daytime illuminance results in a more narrow distribution of sleep timing and circadian phase, and this effect is more pronounced for longer photoperiods. The model results demonstrate that modern lifestyle changes the chronotype distribution towards more eveningness and more extreme differences in eveningness. Such model-based predictions can be used to design guidelines for workplace lighting that help limiting circadian phase differences, and craft new lighting strategies that support human performance, health and wellbeing.

Bright daytime light enhances circadian amplitude in a diurnal mammal.

Mammalian circadian rhythms are orchestrated by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN), which receives information about the 24 h light-dark cycle from the retina. The accepted function of this light signal is to reset circadian phase in order to ensure appropriate synchronization with the celestial day. Here, we ask whether light also impacts another key property of the circadian oscillation, its amplitude. To this end, we measured circadian rhythms in behavioral activity, body temperature, and SCN electrophysiological activity in the diurnal murid rodent Rhabdomys pumilio following stable entrainment to 12:12 light-dark cycles at four different daytime intensities (ranging from 18 to 1,900 lx melanopic equivalent daylight illuminance). R. pumilio showed strongly diurnal activity and body temperature rhythms in all conditions, but measures of rhythm robustness were positively correlated with daytime irradiance under both entrainment and subsequent free run. Whole-cell and extracellular recordings of electrophysiological activity in ex vivo SCN revealed substantial differences in electrophysiological activity between dim and bright light conditions. At lower daytime irradiance, daytime peaks in SCN spontaneous firing rate and membrane depolarization were substantially depressed, leading to an overall marked reduction in the amplitude of circadian rhythms in spontaneous activity. Our data reveal a previously unappreciated impact of daytime light intensity on SCN physiology and the amplitude of circadian rhythms and highlight the potential importance of daytime light exposure for circadian health.

Chromosome-level assembly of southern catfish (silurus meridionalis) provides insights into visual adaptation to nocturnal and benthic lifestyles.

The Southern catfish (Silurus meridionalis) is a nocturnal and benthic freshwater fish endemic to the Yangtze River and its tributaries. In this study, we constructed a chromosome-level draft genome of S. meridionalis using 69.7-Gb Nanopore long reads and 49.5-Gb Illumina short reads. The genome assembly was 741.2Mb in size with a contig N50 of 13.19Mb. An additional 116.4Gb of Bionano and 77.4Gb of Hi-C data were applied to assemble contigs into scaffolds and further into 29 chromosomes, resulting in a 738.9-Mb genome with a scaffold N50 of 28.04Mb. A total of 22,965 protein-coding genes were predicted from the genome with 22,519 (98.06%) genes functionally annotated. Comparative genomic and transcriptomic analyses revealed a rod-dominated visual system which was responsible for scotopic vision. The absence of cone opsins SWS1 and SWS2 resulted in the lack of ultraviolet and blue violet sensitivity. Mutations at key amino acid sites of RH1.1, RH1.2 and RH2 resulted in spectral tuning good for dim light vision and narrow colour vision. A higher expression level of rod phototransduction genes than that of cone genes and higher rod-to-cone ratio led to higher optical sensitivity under dim light conditions. In addition, analysis of the genes involved in eye morphogenesis and development revealed the loss of some conserved noncoding elements, which might be associated with the small eyes in catfish. Together, our study provides important clues for the adaptation of the catfish visual system to the nocturnal and benthic lifestyles. The draft genome of S. meridionalis represents a valuable resource for studies of the molecular mechanisms of ecological adaptation.

Investigating the Indoor Performance of Planar Heterojunction Based Organic Photovoltaics

Recently, the bulk heterojunction (BHJ)-based photoactive layer has been favored over the planar heterojunction (PHJ)-based photoactive layer for organic photovoltaics (OPVs), owing to the evitable thickness limit of the latter induced by the low mobility of charge carriers. However, under dim indoor light conditions, the PV performance becomes immune to the resistive components of the PHJ OPVs, such as a thick photoactive layer, thereby rendering them attractive for operating indoors. In this study, we devise and demonstrate indoor OPVs with a PHJ-based photoactive layer constituting poly(3-hexylthiophene-2,5-diyl) (P3HT) and indene-C60 bisadduct (ICBA). The performance of the PHJ OPVs was optimized by modulating the thickness of the ICBA layer under a 1000 lx light-emitting diode lamp. OPVs with a 65 nm-thick ICBA layer exhibited excellent indoor performance with a power conversion efficiency of 15.3 ± 0.3%, comparable to that of the reference BHJ OPVs (15.0 ± 0.2%). No noticeable performance degradation was observed by increasing the thickness of the PHJ-based photoactive layer; instead, a thick photoactive layer only enhanced the light absorption, resulting in excellent indoor performance with a higher photocurrent.