Semitransparent Organic Photovoltaics Research Articles

Semitransparent organic photovoltaics enabled by transparent p-type inorganic semiconductor and near-infrared acceptor

Semitransparent organic photovoltaics (STOPVs) have gained wide attention owing to their promising applications in building-integrated photovoltaics, agrivoltaics, and floating photovoltaics. Organic semiconductors with high charge carrier mobility usually have planar and conjugated structures, thereby showing strong absorption in visible region. In this work, a new concept of incorporating transparent inorganic semiconductors is proposed for high-performance STOPVs. Copper(I) thiocyanate (CuSCN) is a visible-transparent inorganic semiconductor with an ionization potential of 5.45 eV and high hole mobility. The transparency of CuSCN benefits high average visible transmittance (AVT) of STOPVs. The energy levels of CuSCN as donor match those of near-infrared small molecule acceptor BTP-eC9, and the formed heterojunction exhibits an ability of exciton dissociation. High mobility of CuSCN contributes to a more favorable charge transport channel and suppresses charge recombination. The control STOPVs based on PM6/BTP-eC9 exhibit an AVT of 19.0% with a power conversion efficiency (PCE) of 12.7%. Partial replacement of PM6 with CuSCN leads to a 63% increase in transmittance, resulting in a higher AVT of 30.9% and a comparable PCE of 10.8%.

Reliability of colorfast semitransparent organic photovoltaics

Reliability of colorfast semitransparent organic photovoltaics

Examining the effect of different photovoltaic modules on cucumber crops in a greenhouse agrivoltaic system: A case study

Agrivoltaic systems, a fusion of agriculture and photovoltaic (PV) technology, have emerged as a sustainable solution to optimise land use by enabling simultaneous solar energy and agricultural harvesting. The experiments were conducted in a polytunnel greenhouse in Kfar Qara, Israel, deploying three types of semi-transparent solar PV panels—bifacial glass-encapsulated silicon, bifacial plastic-encapsulated silicon, and semi-transparent organic photovoltaics (OPVs) installed above the plant canopy. The impact of these PV treatments on cucumber crops was evaluated and juxtaposed against a control greenhouse with no panels, over the spring season from February to June 2022. Key growth and yield metrics were recorded during 17 harvests between April 10 and June 2, 2022. The findings revealed a negligible decline in crop yield across PV panel treatments compared to the control. Notably, the control and glass-encapsulated silicon PV treatments demonstrated an increase in yield, growth, and fruit quality. Moreover, the glass-encapsulated silicon PV panels outperformed the plastic-encapsulated and OPV module power conversion in the high heat and humidity of the greenhouse environment. This study accentuates the potential of integrating glass-encapsulated silicon PV panels in polytunnel greenhouses, heralding a promising avenue for bolstering agrivoltaic applications by ensuring a harmonious balance between agricultural yield and electrical energy production.

Self-Assembled Interlayer Enables High-Performance Organic Photovoltaics with Power Conversion Efficiency Exceeding 20.

Interfacial layers (ILs) are prerequisites to form the selective charge transport for high-performance organic photovoltaics (OPVs) but mostly result in considerable parasitic absorption loss. Trimming the ILs down to a mono-molecular level via the self-assembled monolayer is an effective strategy to mitigate parasitic absorption loss. However, such a strategy suffers from inferior electrical contact with low surface coverage on rough surfaces and poor producibility. To address these issues, here, the self-assembled interlayer (SAI) strategy is developed, which involves a thin layer of 2-6nm to form a full coverage on the substrate via both covalent and van der Waals bonds by using a self-assembled molecule of 2-(9H-carbazol-9-yl) (2PACz). Via the facile spin coating without further rinsing and annealing process, it not only optimizes the electrical and optical properties of OPVs, which enables a world-record efficiency of 20.17% (19.79% certified) but also simplifies the tedious processing procedure. Moreover, the SAI strategy is especially useful in improving the absorbing selectivity for semi-transparent OPVs, which enables a record light utilization efficiency of 5.34%. This work provides an effective strategy of SAI to optimize the optical and electrical properties of OPVs for high-performance and solar window applications.

Identifying and Amplifying the Spontaneously Formed Photo‐Charge Contribution in Opaque and Semitransparent Organic Photovoltaics

AbstractSpontaneous photo‐charge (SP) generation within the non‐fullerene (NFA) bulk helps avoid exciton (EX) related loss as compared to the traditional heterojunction route in organic solar cells (OSCs). Unfortunately, the promising SP utilization attracts little attention at this time due to the lack of knowledge on its specific contribution to the photovoltaic performance and rational optimization in high‐efficiency devices. To fill the gap, the NFAs’ SP characteristics are related with their photocurrent loss and power conversion efficiency (PCE) in state‐of‐the‐art materials. Though higher SP population is good for efficient EX utilization, it simultaneously acts as an additional photo‐charge recombination channel. The former can be further enhanced by increasing the NFAs’ crystallinity with preferred lamellar growth, and the latter can be suppressed via electric doping. With the aid of the two‐step optimization strategy, the total photocurrent loss is reduced from 14.4% to 4.8%, accompanying with PCE increment from 16.9% to 18.5%. The SP utilization strategy is finally applied in the semitransparent OSCs (ST‐OSCs), due to its less heterojunction area sensitive photo‐charge generation characteristic. A light utilization efficiency (LUE) is then increased from 3.21% to 3.77%. The findings highlight the pursue of efficient SP utilization as a new design philosophy in future OSCs’ progresses.

Boosting the Performances of Semitransparent Organic Photovoltaics via Synergetic Near-Infrared Light Management.

Semitransparent organic photovoltaics (ST-OPVs) offer promising prospects for application in building-integrated photovoltaic systems and greenhouses, but further improvement of their performance faces a delicate trade-off between the two competing indexes of power conversion efficiency (PCE) and average visible transmittance (AVT). Herein, the authors take advantage of coupling plasmonics with the optical design of ST-OPVs to enhance near-infrared absorption and hence simultaneously improve efficiency and visible transparency to the maximum extent. By integrating core-bishell PdCu@Au@SiO2 nanotripods that act as optically isotropic Lambertian sources with near-infrared-customized localized surface plasmon resonance in an optimal ternary PM6:BTP-eC9:L8-BO-based ST-OPV, it is shown that their interplay with a multilayer optical coupling layer, consisting of ZnS(130nm)/Na3AlF6(60nm)/WO3(100nm)/LaF3(50nm) identified from high-throughput optical screening, leads to a record-high PCE of 16.14% (certified as 15.90%) along with an excellent AVT of 33.02%. The strong enhancement of the light utilization efficiency by ≈50% as compared to the counterpart device without optical engineering provides an encouraging and universal pathway for promoting breakthroughs in ST-OPVs from meticulous optical design.

High‐Performance Organic Photovoltaics Incorporating Bulk Heterojunction and p–i–n Active Layer Structures

In the past five years, significant advancements in the development of novel conjugated polymer donors (D) and non‐fullerene acceptors (A), such as small molecules, have substantially boosted the power conversion efficiency of bulk heterojunction (BHJ) organic photovoltaics (OPVs) devices to over 19%. Recently, in the pursuit of broader impact and heightened efficiency for OPVs, an alternative processing approach has emerged; this approach involves a sequential deposition (SD) technique or a layer‐by‐layer method, creating active layers with p–i–n structures (p and n stand for D and A region, respectively; i stands for BHJ region). Notably, this SD method is particularly effective in semitransparent organic photovoltaics (ST‐OPVs), despite the material requirements it entails. SD‐processing methods enable the creation of vertical multiple junctions and controllable D/A interfaces, facilitating exciton dissociation and charge transport through a well‐designed pseudo p–i–n structure. Furthermore, ST‐OPVs can be integrated into building‐incorporated photovoltaic modules, offering potential applications in greenhouses and agricultural modernization. This integration allows for the comprehensive utilization of solar spectrum energy. In this review, current literature is consolidated on new materials, such as conjugated polymers and non‐fullerene small molecules as electron‐donating and electron‐withdrawing materials, aimed at high‐efficiency OPVs and ST‐OPVs with BHJ‐ and p–i–n structured active layers, and perspectives are offered for future developments.

Semitransparent Organic Photovoltaics Utilizing Intrinsic Charge Generation in Non-Fullerene Acceptors.

In organic semiconductors, a donor/acceptor heterojunction is typically required for efficient dissociation of excitons. Using transient absorption spectroscopy to study the dynamics of excited states in non-fullerene acceptors (NFAs), it is shown that NFAs can generate charges without a donor/acceptor interface. This is due to the fact that dielectric solvation provides a driving force sufficient to dissociate the excited state and form the charge-transfer (CT) state. The CT state is further dissociated into free charges at interfaces between polycrystalline regions in neat NFAs. For IEICO-4F, incorporating just 9 wt% donor polymer PTB7-Th in neat films greatly boosts charge generation, enhancing efficient exciton separation into free charges. This property is utilized to fabricate donor-dilute organic photovoltaics (OPV) delivering a power conversion efficiency of 8.3% in the case of opaque devices with a metal top-electrode and an active layer average visible transmittance (AVT) of 75%. It is shown that the intrinsic charge generation in low-bandgap NFAs contributes to the overall photocurrent generation. IEICO-4F-based OPVs with limited PTB7-Th content have high thermal resilience demonstrating little drop in performance over 700h. PTB7-Th:IEICO-4F semitransparent OPVs are leveraged to fabricate an 8-series connected semitransparent module, demonstrating light-utilization efficiency of 2.2% alongside an AVT of 63%.

Colorful Semitransparent Organic Photovoltaics with Record Key Parameters by Optimizing Photon Utilization and Fabry‐Pérot Resonator Electrode

AbstractDonor PM6 and acceptor L8‐BO are employed to build semitransparent organic photovoltaics (ST‐OPVs). Opaque OPVs are fabricated by tuning the spin‐coating speed of PM6:L8‐BO solution to optimize the photon utilization by balancing photon harvesting and photogenerated carrier collection. The optimal opaque OPVs exhibit relatively high fill‐factor (FF) of 77.58% and power conversion efficiency (PCE) of 15.07%, the average visible transmittance (AVT) of corresponding PM6:L8‐BO films arrives to 53.25%, indicating great potential in realizing efficient ST‐OPVs. ST‐OPVs are built with 1 nm Au/(10, 15, 20, 25 nm) Ag as cathode, exhibiting the PCE/AVT of 11.53%/22.57%, 13.20%/14.24%, 14.28%/9.34%, and 14.71%/6.77%, respectively. Colorful ST‐OPVs are achieved by coupling different Ag/LiF/Ag Fabry‐Pérot (F‐P) resonator microcavity. Green ST‐OPVs with varied color coordinates are achieved by fixing LiF layer thickness as 110 nm and varying Ag layers′ thickness, originating from the adjusted transmittance spectra of green ST‐OPVs. Upon fixing Ag layers′ thickness as 15/25 nm and varying LiF layer thickness as 90, 110, and 145 nm, ST‐OPVs present colors of blue, green, and red with corresponding transmittance peak at 474, 553, and 657 nm. The corresponding PCE/peak transmittance (Tpeak) values arrive to 13.80%/37.8%, 13.31%/28.4%, and 13.20%/27.7%, which should be the best performance among reported colorful ST‐OPVs.

Semitransparent Organic Solar Cells with Homogeneous Transmission and Colorful Reflection Enabled by an ITO-Free Microcavity Architecture.

Semitransparent organic photovoltaics (ST-OPVs), owing to the merits of high power generation, thermal insulation, and aesthetic features, have become a promising candidate for intellectual building- integrated photovoltaic windows. However, the traditional optical evaluation only focuses on the transmission properties and ignores the reflection behaviors. And the lack of quantitative descriptions for array appearance hinders implementation of ST-OPV based large-area modules. To tackle with these issues, an indium tin oxide (ITO)-free optical microcavity architecture into ST-OPVs for achieving high homogeneity in transmittance with controllable reflective appearances through tunning the thickness of individual component layers is introduced. A set of parameters based on optical characteristics of sub-units to provide a quantitative description for the transmittance brightness, transmissive and reflective color purity, and versatility of optical arrays, is further proposed. The optical simulations reveal that reflection modulation from blue to red colors can be realized for devices based on various bulk-heterojunction material systems through regulating the thickness of active layers and antireflection coatings. This work offers a viable design strategy for ST-OPVs toward applications in next-generation smart photovoltaic windows.

Fully Printed and Industrially Scalable Semitransparent Organic Photovoltaic Modules: Navigating through Material and Processing Constraints

While the power conversion efficiency (PCE) of organic photovoltaics (OPV) on small‐area lab cells has rapidly increased during the last few years, the performance on module level and the availability of OPV modules on the market is still limited, primarily due to specific constraints imposed by the industrial production process. This work deals with the upscaling process of latest‐generation OPV from small‐area lab cells to fully solution‐processed modules, which are compatible to industrial roll‐to‐roll (R2R) printing. This transfer is demonstrated step by step from material selection and process optimization for every single layer of the stack (photoactive layer, charge transporting layers, and solution‐processed top electrode)–including long‐term stability investigations (thermal and light)–to scaling up the device area by a factor of >100. Thus, a semitransparent OPV module with 10.8% PCE on 10.2 cm2 active area is achieved, which is among the highest performances for semitransparent, fully solution‐processed OPV modules. The individual developments all meet the requirements for industrial R2R printing (green solvents, processing in air, annealing ≤140 °C, etc.), which ensures that both the optimized layer stack and the fabrication process are fully scalable and easily transferable to large‐scale production.

Comparative analysis of outdoor energy harvest of organic and silicon solar modules for applications in BIPV systems

Organic photovoltaics (OPV) have the potential to fill niches that traditional silicon photovoltaics (Si-PV) have left open so far. Building-integrated photovoltaics (BIPV) is one key area where OPV modules can play a vital role due to their functional attributes of semitransparency, flexibility, and lightweight. However, the architectural constraints and physical layout of buildings often do not allow the installation of photovoltaic (PV) modules at their optimal angles. Herein, we report the outdoor energy harvest of commercial OPV, and monocrystalline silicon (m-Si) modules mounted at inclinations of 45° and 90°, using the ISOS-O2 protocol as a test standard. The semitransparent OPV modules incorporating a P3HT:PCBM bulk heterojunction absorbing layer were found to offer daily specific energy yields (YF) that are 10–15% higher than those of the m-Si modules at 45° inclination. For vertical (90°) mounting, the YF of the OPV modules is even 24–30% higher than that of their inorganic counterparts, thus making them ideally suited for façade integrated BIPV. Laboratory investigations reveal that the superior performance of OPV modules in the vertical position is mainly due to a strongly enhanced fill factor (FF) at reduced in-plane irradiance. At a 45° inclination, the positive temperature coefficient of the OPV modules also plays an important role during high-irradiance hours.

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.

Ultra-flexible semitransparent organic photovoltaics

Ultra-flexible organic photovoltaics (OPVs) are promising candidates for next-generation power sources owing to their low weight, transparency, and flexibility. However, obtaining ultra-flexibility under extreme repetitive mechanical stress while maintaining optical transparency remains challenging because of the intrinsic brittleness of transparent electrodes. Here, we introduce strain-durable ultra-flexible semitransparent OPVs with a thickness below 2 μm. The conformal surface coverage of nanoscale thin metal electrodes (< 10 nm) is achieved, resulting in extremely low flexural rigidity and high strain durability. In-depth optical and electrical analyses on ultrathin metal electrodes showed that the devices maintain over 73% of their initial efficiency after 1000 cycles of repetitive compression and release at 66% compressive strain, and the average visible light transmittances remain higher than 30%. To our knowledge, this is the first systematical study on mechanical behaviors of strain-durable ultra-flexible ST-OPVs through precise adjustment of each ultrathin electrode thickness toward the emergence of next-generation flexible power sources.

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.

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.

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.