Semitransparent Photovoltaics Research Articles

Uncertainty analysis of annual daylight metrics and energy yield weighting factors in optimising photovoltaic window orientation

Application of semi-transparent photovoltaic (PV) windows in buildings has now become an emerging trend towards sustainable design practice. Such application requires a careful thought on finding the optimum window orientation. From the perspective of energy generation, equator-facing orientation is the best option. However, such orientation may lead to glare and visual discomfort. To solve this problem, optimisation is required, but the outcome often depends on the weighting factors of each metric considered. This study therefore aims to quantify the uncertainty of weighting factors in optimising PV window orientation, by considering various annual daylight metrics and energy yield. Computational modelling and simulation using Rhinoceros and Grasshopper were performed for a building prototype with a single, semi-transparent monocrystalline PV window, under the climate of Gowa, Indonesia (5.2°S). Weighting factor for each metric was randomised using Monte Carlo simulation for 1000 scenarios, and the uncertainty were analysed. When all metrics are considered, on average, the South orientation appears as the best orientation in 73% of the cases, followed by East (24%) and North (3%). When a single metric is assigned to each metric group, the South orientation still appears as the best orientation in 62% of the cases.

High‐Performance Colorful Organic Photovoltaics with Microcavity Resonance Color Filter

AbstractMicrocavity resonance is an effective technique for making promising semitransparent organic photovoltaics (ST‐OPVs) even more aesthetically attractive with high color saturation, by tailoring the visible transmittance spectrum to narrow the transmission peak. In this study, a distinctive microcavity resonance color filter (CF) structure of silver/ bismuth(III) fluoride /silver (Ag/BiF3/Ag) is integrated upon the rear transparent electrode, which simultaneously achieves high color purity and high power conversion efficiency (PCE) for colorful OPVs. By precisely regulating the thickness of the BiF3 layer, colorful OPVs with a wide color gamut and high color purity are achieved, including the colors of indigo, blue, bluish‐green, green, orange, and red, as well as compound color devices with dual or multiple transmission peaks in the visible region. A recorded PCE of 16.27% is obtained for the indigo OPV, with the Commission Internationale de l´Eclairage 1931 coordinates of (0.164 and 0.087) and a maximum transmittance of 18.7% at the transmission peak wavelength of 393 nm. Furthermore, colorful OPVs as color reflectors are systematically investigated under different light incident surfaces. The improved stability of colorful OPVs is attributed to the excellent moisture resistance of BiF3. The colorful OPVs with desired transmitted/reflected colors, and wide color gamut show great potential for future energy harvesting solutions.

P-type Polymers in Semitransparent Organic Photovoltaics.

P-type polymers are polymeric semiconducting materials that conduct holes and have extensive applications in optoelectronics such as organic photovoltaics. Taking the advantage of intrinsic discontinuous light absorption of organic semiconductors, semitransparent organic photovoltaics (STOPVs) present compelling opportunities in various potential applications such as building-integrated photovoltaics, agrivoltaics, automobiles and wearable electronics. The characteristics of p-type polymers, including optical, electronic and morphological properties, determine the performance of STOPVs, and the requirements for p-type polymers differ between opaque organic photovoltaics and STOPVs. Hence, in this Minireview, recent advances of p-type polymers used in STOPVs are systematically summarized, with emphasis on the effects of chemical structures, conformation structures and aggregation structures of p-type polymers on the performance of STOPVs. Furthermore, new design concepts and guidelines are also proposed for p-type polymers to facilitate the future development of high-performance STOPVs.

P‐type Polymers in Semitransparent Organic Photovoltaics

AbstractP‐type polymers are polymeric semiconducting materials that conduct holes and have extensive applications in optoelectronics such as organic photovoltaics. Taking the advantage of intrinsic discontinuous light absorption of organic semiconductors, semitransparent organic photovoltaics (STOPVs) present compelling opportunities in various potential applications such as building‐integrated photovoltaics, agrivoltaics, automobiles, and wearable electronics. The characteristics of p‐type polymers, including optical, electronic, and morphological properties, determine the performance of STOPVs, and the requirements for p‐type polymers differ between opaque organic photovoltaics and STOPVs. Hence, in this Minireview, recent advances of p‐type polymers used in STOPVs are systematically summarized, with emphasis on the effects of chemical structures, conformation structures, and aggregation structures of p‐type polymers on the performance of STOPVs. Furthermore, new design concepts and guidelines are also proposed for p‐type polymers to facilitate the future development of high‐performance STOPVs.

Dual Photonic Structures Enable High‐Performance Semitransparent Organic Photovoltaics with Enhanced Light Utilization

Semitransparent organic photovoltaics (ST‐OPVs) offer promising prospects for self‐powered greenhouses and building‐integrated photovoltaic systems. However, a remaining critical challenge is to balance the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, a synergetic strategy of light manipulation is developed to achieve high‐performance ST‐OPVs by employing dual photonic structures with a rear single‐layer optical coupling layer (OCL) and a front single‐layer antireflection coating (ARC). The material selection and thickness optimization of both OCL and ARC are systematically guided by combining theoretical simulations and experimental devices, leading to significantly enhanced light utilization in ST‐OPVs. As a result, the use of dual photonic structures enables ST‐OPVs based on the active layer of PM6:Y6 to demonstrate simultaneously a high AVT of 35.7% and a good PCE of 10.29%, yielding an excellent light utilization efficiency of 3.67% with a remarkable improvement of 43% comparing with that of the control device. This work provides a simple yet effective strategy of light manipulation for the development of high‐performance ST‐OPVs.

Design and thermal performance of an innovative greenhouse

The study presents the design and thermal performance evaluation of a novel solar greenhouse with humidification-dehumidification unit, water-cooled heat exchanger and variable mixing ratio in the Mediterranean climate. The greenhouse is designed to provide proper microclimatic conditions for crops, produce fresh water through condensing water vapor released from the plants, and save energy using the semitransparent PV panels. Results showed that on a typical summer day, the solar greenhouse ensures proper microclimatic conditions all day long by reducing the temperature by 11.14 °C compared to conventional greenhouses, while maintaining acceptable values of relative humidity and producing 70 L of fresh water per day. An operation schedule was established based on varying return-to-fresh air ratio to ensure optimal system performance. The operation schedule showed that proper microclimatic conditions can be reached through ventilation for 13 h per day. To enhance the net-energy performance, the produced water can be used for irrigation and the return air can be used for cooling the PV panels.

Efficient and Thermally Stable Wide Bandgap Perovskite Solar Cells by Dual‐Source Vacuum Deposition

AbstractWide bandgap perovskites are being widely studied in view of their potential applications in tandem devices and other semitransparent photovoltaics. Vacuum deposition of perovskite thin films is advantageous as it allows the fabrication of multilayer devices, fine control over thickness and purity, and it can be upscaled to meet production needs. However, the vacuum processing of multicomponent perovskites (typically used to achieve wide bandgaps) is not straightforward, because one needs to simultaneously control several thermal sources during the deposition. Here a simplified dual‐source vacuum deposition method to obtain wide bandgap perovskite films is shown. The solar cells obtained with these materials have similar or even larger efficiency as those including multiple A‐cations, but are much more thermally stable, up to 3500 h at 85 °C for a perovskite with a bandgap of 1.64 eV. With optimized thickness, record efficiency of >19% and semitransparent devices with stabilized power output in excess of 17% are achieved.

Transfer-printing a surface-truncated photonic crystal for multifunction-integrated photovoltaic window

Precise light manipulation is of paramount importance in improving the performance of semi-transparent organic photovoltaics (STOPVs) for their orientation toward building-integrated photovoltaic window. Nevertheless, one critically important issue for the integration of optical modulation with STOPV devices, lies in the damage from the harsh direct deposition steps to the intrinsic properties and long-term durability of STOPVs. Here a transfer-printing (TP) approach, in which photonic crystals (PC) films are deposited onto a self-adhesive and flexible matrix for their integration with STOPV devices, was first reported, enabling the resultant TPPC-STOPV devices with superior optical-related multifunction. In contrast to these devices based on direct-evaporated PC film, the non-encapsulated TPPC-STOPVs present an ultraviolet blocking (UVB) as high as 96%, an infrared rejection (IRR) of 92%, an enhanced power conversion efficiency (PCE) by 5% as well as superior long-term durability as 96% of its initial PCE. Their gifted superior UVB and IRR properties are individually on a par with those of the stat-of-the-art commercial optical films for smart solar window. This transfer-printing approach makes it possible to separate the high-energy fabrication of high-quality contacts from target optoelectronic devices, providing a wide range of possibilities for the integration of high-quality contacts with optoelectronic devices, including organic, silicon and perovskite optoelectronic devices, as well as their large-area flexible integration.

Experimental Characterization of the Optical Performance of Concentrating Photovoltaic Glazing (CoPVG) Systems

An experiment was conducted to test the optical efficiency of the lenses of the Concentrating Photovoltaic Glazing (CoPVG) concept. The CoPVG is a seasonal glazing system consisting of longitudinal prismatic lenses. The lenses concentrate sunlight onto the focus where Photovoltaic (PV) cells are bonded, generating electricity while simultaneously preventing excessive glare indoors during summer. The system transmits sunlight for daylight purposes in winter. The experimental results were compared with an analytical model developed at Ulster University. Although there were discrepancies between the model and the experimental results, the model can still predict the optical performance of the lenses reliably, and can therefore still provide an overview of the concept’s optical performance. The model was then used to create a visual representation of the glazing’s annual optical performance, demonstrating how the glazing responds to changes in the sun’s position in the sky throughout the year. This analysis allows for balancing the need for natural lighting and energy generation, and so enables designers to evaluate annual optical performance of the CoPVG lens quickly and accurately. A case study of a building in Belfast is presented to demonstrate the application of the model. As an example, the results indicate that utilizing the lenses in glazing towards the south leads to a shift in its performance from room lighting to shading on 1st April, and vice versa on 15 September. The analyses also show that utilizing the CoPVG lenses can potentially enhance the electrical output power of the glazing ranging between 5% and 8% and from 46% up to 52% during winter and summer, respectively, compared with traditional Semi-Transparent Photovoltaic (STPV) glazing with the same opaque area percentage.

High Efficiency Transparent and Semi‐Transparent Photovoltaics Based on a Layer‐By‐Layer Deposition

Transparent and semitransparent photovoltaics offer an exciting opportunity to integrate existing infrastructure with renewable energy. Organic photovoltaics (OPVs) are key enablers for wavelength‐selective transparent photovoltaics (TPVs) because of their selective absorption in the near‐infrared (NIR) that enables simultaneously high power conversion efficiency (PCE) and average visible transmittance (AVT). The recent rise of OPVs and TPVs has been accelerated in large part by the development of nonfullerene acceptors (NFAs) as highly adaptable deep NIR harvesting materials. Herein, sequential layer‐by‐layer (LBL) deposition of a selectively NIR absorbing nontraditional acceptor polymer is paired with a NIR absorbing donor IEICO‐4F that is typically considered an NFA via solvent orthogonality. With detailed optimization of the active layers and top electrode, semi‐transparent photovoltaics with a PCE of 8.8%, AVT of 40.9%, and a light utilization efficiency of 3.6% are demonstrated. The LBL approach enables explicit optical modeling of the device structure to extract exciton diffusion lengths >100 nm for both the polymer and IEICO‐4F with a transition in charge collection length regimes dependent on the acceptor thickness. Furthermore, the LBL deposition technique enables an investigation of the full range of polymer thickness and its impact on power generation and optical performance.

Effect of semi-transparent a-Si PV glazing within double-skin façades on visual and energy performances under the UK climate condition

Various studies have assessed the energy performance alterations affected by the novel technology of Building-Integrated Photovoltaic in Double-Skin Facades (BIPV-DSF), while lighting performance tied to the BIPV-DSF has not received much attention. This paper provides numerical modelling to assess the effect of BIPV-DSF on both indoor visual condition and energy consumption for an office module under a typical climate in the United Kingdom. The proposed study was focused on the comparisons between a reference case (a DSF office module with both layers using clear double glazing) and a design case of the same office module with BIPV-DSF using semi-transparent Amorphous Silicon PV glazing. Results show a significant drop in maximum daylight illuminance of 73% by configuring the BIPV-DSF with reference to the regular DSF. It was also reported the resultant average and minimum daylight factors (0.65% and 0.00%) were not able to meet indoor visual comfort requirements for office environments. Furthermore, it was found that the use of BIPV-DSF resulted in a net increase of 8% in building energy consumption over the reference DSF. Therefore, it is concluded that in the present context the BIPV-DSF is not viable for a commercial installation under the UK's climate conditions.

Achieving sustainability of greenhouses by integrating stable semi-transparent organic photovoltaics

Achieving sustainability of greenhouses by integrating stable semi-transparent organic photovoltaics

Spectral Engineering: The Key to High‐Performance Semitransparent Organic Photovoltaics

With the rapid development of organic photovoltaics (OPVs) in recent years, they are getting closer to industrialization. Semitransparency is a unique feature of OPVs, thus semitransparent OPVs (STOPVs) are regarded as one of the most promising directions for industrialization. However, there is a contradiction between the power conversion efficiency and visible transparency of STOPVs, as well as the need to further optimize the specific wavelength transmission and color index for practical applications. Spectral engineering is of high significance to solve the above issues. In this perspective, the recent research progress on spectral engineering for STOPVs from the views of material design, active layer engineering, and optical management is systematically summarized. The potential applications that utilize the different spectral features of STOPVs in agriculture, buildings, vehicles, and floating photovoltaics are introduced. Challenges and future research directions that promote the commercialization of STOPVs are also proposed.

Performance assessment of double pass photovoltaic/thermal solar air collector using bifacial PV with CPC and mirror reflector under Malaysian climate

The performance of photovoltaic thermal (PV/T) type solar collectors can be optimised with the use of bifacial photovoltaic panel since it can utilise the absorbed incident solar irradiance from its front and rear surface. However, its potential is highly determined by the amount of the reflected solar irradiance onto the rear surface of the panel. In this research, we assessed the potential of a novel double pass photovoltaic/thermal (PV/T) solar air collector using semi-transparent bifacial PV panel with compound parabolic concentrator and mirror reflector in Malaysia. The use of CPC and reflector was introduced to increase the amount of reflected light and hence increasing the efficiency of the collector. A mathematical model was developed, and validated o predict the performance of the solar collector. Using the validated mathematical model, the optimum mass flow rate of the bifacial PV/T collector with CPC and mirror reflector was found at 0.0589 kg/s. At this flow rate, when operated under the hot climate of Malaysia, the temperature output of as high as 51 °C is achievable implying its potential as a preheated air to regenerate desiccant materials in solar assisted cooling system and for agriculture drying application. Also, when compared with the bifacial PV/T solar collector without the CPC, the total energy useful was found almost 40% higher.

Determining the optimal visible light transmittance of semi-transparent photovoltaic considering energy performance and occupants’ satisfaction

With the increasing use of front windows such as curtain walls, the application of semi-transparent photovoltaic (STPV) systems is effective in producing renewable energy, reducing cooling load via solar radiation control, and improving visual comfort. However, in STPV, the visibility of the view from a window decreases, and this can have a negative impact on the occupants' satisfaction (i.e., psychological satisfaction, task performance, and task load). Therefore, this study sought to present the optimal visible light transmittance (VLT) of STPV that simultaneously considers energy performance and the occupants' satisfaction according to the azimuth of a building. To this end, a residential building in South Korea was selected, and energy performance according to the VLT of STPV (amorphous Si thin film PV) was analyzed using DesignBuilder and EnergyPlus for STPV with three VLTs (i.e., 10%, 20%, and 30%). In order to analyze the occupants' satisfaction according to the VLT of STPV, 31 participants were recruited, and an experiment using virtual reality (VR) was carried out. Multi-objective optimization was performed using the energy performance, psychological satisfaction, and task load. The results showed that as the weight of energy performance was adjusted to 0.33, 0.5, and 0.6, the optimal VLT of STPV was 25.53%, 22.65%, and 20.85% on average, respectively. It is expected that the findings of this study can allow the building owner or building designer to predict the energy performance, the occupants’ psychological satisfaction and task load according to the VLT of STPV.

Daylight oriented optimization of photovoltaic integrated skylights for railway station waiting hall represented large space buildings in China

Photovoltaic Integrated Skylights (SIPVs) have been widely used due to their unique synergistic benefits of shading and power generation. Their variable shading and light transmission properties upon varying lighting climates could aggravate the complexity of the daylighting conditions, especially when applied to large space public building skylights. In this study, Chinese cities Lhasa and Beijing were selected as representative cities for semi-transparent photovoltaic (STPV) skylight surveys corresponding to high and moderate solar radiation levels. Railway station waiting halls as the typical large space building, together with SIPVs in varying distribution modes and skylight-to-roof ratios (SRRs) have been modeled and examined. By the aid of dynamic daylighting indicator metrics and DAYSIM simulation tool, this work verified critical roles that SIPV SRRs play in indoor daylighting qualities, for both centralized and uniserial array skylight distributions. As a result, 30 % ∼ 35 % and 23 % ∼ 30 % were determined as the best value ranges for centralized SIPVs, while 16.52 % ∼ 19.27 % and 11.01 % ∼ 19.27 % were confirmed as the best value range for uniserial array distributed SIPVs, for Beijing and Lhasa accordingly. For the first time SIPV SRR based design recommendations considering both typical distribution modes had been concluded for railway station represented large space buildings, for Lhasa and Beijing represented daylighting climates or similarities. The research outcomes can assist more effective SIPV designs and daylight optimizations for such large space type public buildings.

A paradigm study of polymer donor diluted bulk heterojunction films for application in semitransparent organic photovoltaics

More J-type polymer aggregations and the prioritized polymer reduction from its pure domain help to achieve high LUE in ST-OSCs during the polymer donor diluting process.

Intrinsically stretchable, semi-transparent organic photovoltaics with high efficiency and mechanical robustness via a full-solution process

AZO@Ag nanowire@AZO (AAA) composite stretchable transparent electrode enables full-solution-processed semi-transparent intrinsically stretchable OPV achieving record 10.90% PCE, with excellent mechanical robustness against stretch-release cycles.

Tailoring multifunctional anions to inhibit methanol absorption on a CsPbBr3 quantum dot surface for highly efficient semi-transparent photovoltaics.

Methyl acetate (MeOAc) is the most used antisolvent in the preparation of perovskite quantum dot (QD) films. However, the hydrolysis of MeOAc results in acetic acid and methanol (MeOH), and the decomposition of the perovskite occurs more easily under acidic and polar conditions. Herein, we report a facile and universal anion modification strategy to inhibit MeOH absorption on a perovskite QD surface and improve the photovoltaic performance of perovskite QD solar cells, which is implemented by incorporating a series of guanidinium salts containing different anions (guanidinium bromide (GuaBr), guanidinium thiocyanate (GuaSCN), and guanidinium acetate (GuaAc)). All anions play a positive role in inhibiting the absorption of MeOH on the QD surface, facilitating charge transfer between perovskite QDs and passivating the defects. Moreover, the regulation of surface chemistry can be optimized by rational tailoring of different anion species. The GuaAc-based devices deliver a PCE of 7.04%, which is the highest value among inorganic CsPbBr3 QD solar cells. More importantly, the CsPbBr3 QD solar cells exhibit high transparency over the entire visible spectrum region, indicating their promising application in solar windows.

Effect of novel graphitic carbon/NiO hole transporting electrode on the photovoltaic and optical performance of semi-transparent perovskite solar cells.

Perovskite devices can play a critical role as tunable semi-transparent photovoltaics managing the buildings' energy health for energy harvesting, storage and utilization. Here we report ambient semi-transparent PSCs with novel graphitic carbon/NiO-based hole transporting electrodes having variable thicknesses achieving a highest efficiency of ∼14%. On the other hand, the altered thickness produced the highest average visible transparency (AVT) of the devices, nearly 35%, which also influenced other glazing-related parameters. This study envisages the impact of the electrode deposition technique on indispensable parameters like colour rendering index, correlated colour temperature, and solar factor evaluated using theoretical models to illuminate these CPSCs' colour and thermal comfort for BIPV integration. The solar factor value between 0 to 1, CRI value >80 and CCT value >4000 K make it a significant semi-transparent device. This research work suggests a possible approach to fabricating carbon-based PSC for high-performance semi-transparent solar cells.