Semitransparent Organic Solar Cells Research Articles

Improved performance of ternary organic solar cells based on both bulk and pseudo-planar heterojunction active layer

The high photovoltaic conversion efficiency (PCE) of ternary organic solar cells (OSCs) based on PTB7-Th, PC71BM and IEICO-4F material is obtained, the short-circuit current density (J SC), fill factor (FF), and open-circuit voltage is 25.90 mA cm−2, 73.20% and 0.71 V, respectively. PCE is as high as 13.53%. It is the highest PCE of ternary OSCs based on PTB7-Th, PC71BM and IEICO-4F materials for all we know. The narrow bandgap material of IEICO-4F is deposited on PTB7-Th:PC71BM bulk heterojunction (BHJ) by layer-by-layer process. We constructed the dual bandgap active layer both BHJ and pseudo-planar heterojunction (P-PHJ), it could be defined as ternary BHJ/P-PHJ of OSCs. This type of OSCs is not only the complementary bandgap material of the active layer, but also increasing the donor/acceptor (D/A) interface. The excitons generation and collection of the device are increased leading a higher J SC and FF. The semitransparent OSCs (ST-OSCs) is prepared by varying the thickness of Ag electrode and PCE can reach 9.70%, and the average visible light transmittance and light use efficiency of ST-OSCs are improved effectively.

Optically Enhanced Semitransparent Organic Solar Cells with Light Utilization Efficiency Surpassing 5.5%

AbstractConverting non‐visual light into photocurrent while maintaining high visual transparency is vital for semitransparent organic solar cells (ST‐OSCs) application, yet often challenging over insufficient invisible light‐harvesting. Herein, spectrally selective optical manipulation for ST‐OSCs with high visual light transparency and full‐spectral non‐visual light reflection is proposed by matching the optical admittance of ultrathin Ag films using ZnS and MgF2. The reflection of optically enhanced ST‐OSCs at the spectral region beyond the human eye's response spectrum is improved and the transmission in the visual region is simultaneously enhanced. By further integrating an anti‐reflective structure, the optimal structure boosts the average visible transmittance and power conversion efficiency of ST‐OSCs to 44.3% and 12.6%, respectively, yielding a record light utilization efficiency of 5.6%. Corresponding flexible ST‐OSCs with high mechanical stability implies that this work provides a facile and universal strategy for ST‐OSCs aiming at building integrated photovoltaics.

Recent Progress in Semitransparent Organic Solar Cells: Photoabsorbent Materials and Design Strategies.

The increasing energy demands of the global community can be met with solar energy. Solution-processed organic solar cells have seen great progress in power conversion efficiencies (PCEs). Semitransparent organic solar cells (ST-OSCs) have made enormous progress in recent years and have been considered one of the most promising solar cell technologies for applications in building-integrated windows, agricultural greenhouses, and wearable energy resources. Therefore, through the synergistic efforts of transparent electrodes, engineering in near-infrared photoabsorbent materials, and device engineering, high-performance ST-OSCs have developed, and PCE and average visible transmittance reach over 10% and 40%, respectively. In this review, we present the recent progress in photoabsorbent material engineering and strategies for enhancing the performance of ST-OSCs to help researchers gain a better understanding of structure-property-performance relationships. To conclude, new design concepts in material engineering and outlook are proposed to facilitate the further development of high-performance ST-OSCs.

The Role of Device Architecture and Interfacial Layer on Performance of Semitransparent Organic Solar Cells

Semitransparent organic solar cells (ST‐OSCs) generally suffer from voltage loss in comparison to their opaque counterparts. Herein, ST‐OSCs constructed with conventional and inverted structures have been explored. The voltage losses of the inverted ST‐OSCs are lower than that of the conventional architectures when the thicknesses of the top transparent electrodes approach the percolation threshold, which is attributed to the larger surface energy of the bottom seeding layers, higher built‐in electric fields, and lower recombination losses. Moreover, ST‐OSCs with conventional architectures based on four commonly used electrode transporting layers (ETLs) PDINN, PDINO, PNDIT‐F3N, and PFN‐Br are employed to distinguish the Voc variation when capping with 10 nm top electrodes. It is revealed that ETL with larger surface energy and a stronger ability to reduce the cathode work function is more beneficial for reducing the voltage loss for ST‐OSCs. This work demonstrates the crucial role of device structure and interfacial layers in optimizing the ST‐OSC device performance.

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.

Dithienopyran-based narrow-bandgap donor polymers: Unveiling the potential for semitransparent organic solar cells with enhanced NIR absorption

Semitransparent organic solar cells (ST-OSCs) have recently received considerable attention in the field of photovoltaics owing to their great potential in applications such as building-integrated photovoltaics, self-powered greenhouses, and vehicle coatings. Because the near-infrared (NIR) region is an invisible region whose photon content is higher than that of the visible region, it is preferable to apply photoactive materials with narrow bandgaps in ST-OSCs. Tremendous efforts have been made to develop narrow-bandgap non-fullerene acceptors, however, donor polymers with NIR absorption ability for efficient ST-OSCs have rarely been reported. In this study, two novel narrow-bandgap donor polymers, PDTP-TBT and PDTTP-TBT, are designed and synthesized. Both polymers exhibit strong NIR absorption and high transmittance in the visible region, suggesting their potential for use in ST-OSCs. An opaque OSC with a PDTTP-TBT-based photoactive layer achieves a higher power conversion efficiency (PCE) of 8.87% than a PDTP-TBT-based OSC (PCE of 3.65%) due to its better charge transport characteristics. Furthermore, an ST-OSC using PDTTP-TBT-based blend film exhibits a PCE of 6.72%, average visible transmittance of 43.9%, and light utilization efficiency of 2.95%.

Solid Additive Dual-Regulates Spectral Response Enabling High-Performance Semitransparent Organic Solar Cells.

Semi-transparent organic solar cells (ST-OSCs) possess significant potential for applications in vehicles and buildings due to their distinctive visual transparency. Conventional device engineering strategies are typically used to optimize photon selection and utilization at the expense of power conversion efficiency (PCE); moreover, the fixed spectral utilization range always imposes an unsatisfactory upper limit to its light utilization efficiency (LUE). Herein, a novel solid additive named1,3-diphenoxybenzene (DB) is employed to dual-regulate donor/acceptor molecular aggregation and crystallinity, which effectively broadens the spectral response of ST-OSCsin near-infrared region. Besides, more visible light is allowed to pass through the devices, which enables ST-OSCs to possess satisfactory photocurrent and high average visible transmittance (AVT) simultaneously. Consequently, the optimal ST-OSC based on PP2+DB/BTP-eC9+DB achieves a superior LUE of 4.77%, representing the highest value within AVT range of 40-50%, which also correlates with the formation of multi-scale phase-separated morphology. Such results indicate that the ST-OSCs can simultaneously meet the requirements for minimum commercial efficiency and plant photosynthesis when integrated with the roofs of agricultural greenhouses. This work emphasizes the significance of additives to tune the spectral response in ST-OSCs, and charts the way for organic photovoltaics in economically sustainable agricultural development.

All-solution-processed flexible semitransparent organic solar cells based on sprayed silver nanowire composites as top electrodes

Solution processable transparent top electrodes with good conductivity and high transmittance play a critical role in developing highly efficient semitransparent organic solar cells (ST-OSCs). Herein, a simple low-temperature spray-coating method is proposed to fabricate silver nanowires/zinc oxide nanoparticles (AgNWs/ZnO) composite electrodes. The effects of coverage of ZnO nanoparticles on optoelectronic properties and surface morphologies of the composites are systemically investigated. Compared to the pristine AgNWs, the AgNWs/ZnO composite layer exhibits improved electrical conductivity due to the filling of nanoparticles as well as the capillary force caused during the volatilization of ZnO dispersion. A low sheet resistance of 8.3 Ω/ and a high transmittance of 78.91 % at 550 nm are achieved in the optimized AgNWs/ZnO composite films with excellent thermal and mechanical stabilities. By using the spray-coated AgNWs composite as the top electrode, the PM6:N3 based ST-OSCs prepared on ITO/glass substrate attain a power conversion efficiency (PCE) of 10.88 % and an average transmittance (AVT) of 28.80 % due to the enhanced charge extraction and suppressed trap-assisted recombination. Moreover, fully solution-processed ST-OSCs are fabricated based on AgNWs/ZnO top electrodes, achieving a PCE of 9.01 % and an AVT of 27.8 %. It provides a simple and effective strategy to fabricate transparent flexible top electrodes and may pave the way towards all-solution-processed highly efficient ST-OSCs.

Novel Materials for Semi-Transparent Organic Solar Cells

The rapid development of photovoltaic technology has driven the search for novel materials that can improve the cost-effectiveness and efficiency of solar cells. Organic semiconductors offer unique optical tunability and transparency, allowing customization for the absorption of specific optical spectra like near-infrared radiation. Through the molecular engineering of electron donors and acceptors, these materials can be optimized for targeted optical selectivity. This adaptability enables the development of efficient energy-harvesting devices tailored for specific spectral regions. Consequently, organic semiconductors present a promising avenue for specialized applications such as semi-transparent organic solar cells. This review offers a detailed summary of the latest developments in novel organic semiconductor materials, focusing on design principles and synthesis of materials in the context of semi-transparent organic solar cells. Optimization of molecular architecture, photovoltaic performance, and the optoelectronic properties of these materials has been explored, highlighting their potential for next-generation solar energy conversion.

Collaborative regulation strategy of donor and acceptor analogues realizes multifunctional semitransparent organic solar cells with excellent comprehensive performance

We propose a collaborative regulation strategy of donor and acceptor analogues to develop multi-functional ST-OSCs with highly comprehensive performance.

High-performance semi-transparent organic solar cells driven by the dipole-controlled optoelectrical response of bilateral self-assembled monolayer strategy

A bilateral self-assembled monolayer (SAM) strategy is proposed to improve the performance of both opaque/translucent and rigid/flexible organic solar cells (OSCs), which have great potential for various high-value applications such as portable, building-integrated and vehicle-integrated photovoltaics. By applying the dipole-controlled SAMs to both ITO/ZnO and ZnO/active layer interfaces, the work function of the ZnO electron transport layer was reduced, which improved charge transport and reduced carrier recombination at the interface. The opaque OSCs with the bilateral SAM demonstrated significant performance improvement with power conversion efficiencies (PCEs) reaching 17.20% and 16.96% for rigid and flexible OSCs. When used in semi-transparent OSCs together with MoO3/Ag/MoO3 electrode, in semi-transparent (ST) OSCs, PCE and average visible transmittance (AVT) can be improved simultaneously, and 10.37% PCE and 36.27% AVT demonstrate a remarkable light utilization efficiency (LUE) of 3.85%. Finally, the large area (10 × 10 cm2) ST-OSC module was fabricated and demonstrated a PCE of 8.17% and LUE of 2.5%, among the best-reported values for inverted module devices. The developed bilateral SAM strategy can be useful in developing high-performance OSCs of both opaque/translucent and rigid/flexible types for various practical applications.

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.

Solution Processed Semi-Transparent Organic Solar Cells Over 50% Visible Transmittance Enabled by Silver Nanowire Electrode with Sandwich Structure.

Photovoltaic windows with easy installation for the power supply of household appliances have long been a desire of energy researchers. However, due to the lack of top electrodes that offer both high transparency and low sheet resistance, the development of high-transparency photovoltaic windows for indoor lighting scenarios has lagged significantly behind photovoltaic windows where privacy issues are involved. Addressing this issue, this work develops a solution-processable transparent top electrode using sandwich structure silver nanowires, realizing high transparency in semi-transparent organic solar cells. The wettability and conducting properties of the electrode are improved by a modified hole-transport layer named HP. The semi-transparent solar cell exhibits good see-through properties at a high average visible transmittance of 50.8%, with power conversion efficiency of 7.34%, and light utilization efficiency of 3.73%, which is the highest without optical modulations. Moreover, flexible devices based on the above-mentioned architecture also show excellent mechanical tolerance compared with Ag electrode counterparts, which retains 94.5% of their original efficiency after 1500 bending cycles. This work provides a valuable approach for fabricating solution-processed high transparency organic solar cells, which is essential in future applications in building integrated photovoltaics.

Magnesium fluoride microcavity-based non-fullerene semitransparent organic solar cells with high peak transmittance and low efficiency loss rate

Microcavity-based semitransparent organic solar cells (ST-OSCs) have become a hot issue in the research field of green energy harvesting due to their wider potential applications in colored photovoltaic glass, building-integrated photovoltaics, and so on. However, for this kind of ST-OSCs, high photoelectric conversion efficiency (PCE) and high peak transmittance cannot usually be achieved simultaneously. To circumvent the problem, this paper proposes MgF2 microcavity with a structure of Au/Ag/MgF2/Ag for ST-OSCs so that high peak transmittance can be achieved at low cost of PCE. The device structure of ST-OSCs is Glass/ITO/ZnO/PTB7-Th: IEICO-4F/MoO3/Au/Ag/MgF2/Ag. By combining the high transmittance of MgF2 microcavities with the low absorption of IEICO-4F in the blue light, a colorful ST-OSCs with high blue light transmittance can be obtained. The IEICO-4F in the active layer shows strong optical absorption in the near-infrared wavelength region, but weak absorption in the visible region. The results demonstrate that the peak transmittance of ST-OSCs reached a high value of 48% at 440 nm and the PCE reached 10.4%. Such a high peak transmittance is achieved while the PCE reduction compared to the control opaque device is about 5%. The PCE loss rate at each peak transmittance is the lowest among the reported values for the similar ST-OSCs devices. By adjusting the thickness of MgF2, ST-OSCs with different colors can be obtained, the peak transmittance of which is over 32% and the PCE loss rate is less than 7.25%. This report provides a new approach to solve the trade-off between efficiency and transmittance of ST-OSCs.

Unraveling the Impact of Thickness on Active Layer Morphology and Device Performance of Semitransparent Organic Solar Cells: A Comprehensive Study

Unraveling the Impact of Thickness on Active Layer Morphology and Device Performance of Semitransparent Organic Solar Cells: A Comprehensive Study

In Situ Doping of the PEDOT Top Electrode for All-Solution-Processed Semitransparent Organic Solar Cells.

The development of an ideal solution-processable transparent electrode has been a challenge in the field of all-solution-processed semitransparent organic solar cells (ST-OSCs). We present a novel poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) top electrode for all-solution-processed ST-OSCs through in situ doping of PEDOT:PSS. A strongly polarized long perfluoroalkyl (n = 8) chain-anchored sulfonic acid effectively eliminates insulating PSS and spontaneously crystallizes PEDOT at room temperature, leading to outstanding electrical properties and transparency of PEDOT top electrodes. Doped PEDOT-based ST-OSCs yield a high power conversion efficiency of 10.9% while providing an average visible transmittance of 26.0% in the visible range. Moreover, the strong infrared reflectivity of PEDOT enables ST-OSCs to reject 62.6% of the heat emitted by sunlight (76.7% from infrared radiation), outperforming the thermal insulation capability of commercial tint films. This light management approach using PEDOT enables ST-OSCs to simultaneously provide energy generation and energy savings, making it the first discovery toward sustainable energy in buildings.

Improved Light Utilization Efficiency for an ITO‐Free Semitransparent Organic Solar Cell Using a Multilayer Silver Back Electrode as Infrared Mirror

Semitransparent organic solar cells (STOSCs) exhibit promising application as power‐generating windows in buildings and agricultural greenhouses. Due to unique optical properties of organic semiconductors, they can efficiently absorb near‐infrared light while maintaining a high degree semitransparency in the visible range. Since power conversion efficiency (PCE) and average visible transmission (AVT) frequently stand in a trade‐off relationship, a major challenge in improving the overall performance of STOSCs is maximizing the product of both, called light utilization efficiency (AVT × PCE = LUE). Herein, using multiple layers of aluminium‐doped ZnO (AZO) and silver as an infrared reflecting back electrode, in order to increase current generation while maintaining high visible transparency, is proposed. Using optical modeling, the optimal layer thickness of the AZO layer sandwiched between two Ag layers is determined, leading to an increased photocurrent generation of up to 10%. Simultaneously, experimental findings show that the fill factor decreases with an increasing AZO layer thickness. By adjusting the thickness of the photoactive layer, the blend concentration, and improving the top electrode material the thus‐far highest reported LUE for indium tin oxide‐free STOSCs is attained, reaching 4.0% with a PCE of 8.7% and an AVT of 46.3%.

A Review of the Improvements in the Performance and Stability of Ternary Semi-Transparent Organic Solar Cells: Material and Architectural Approaches

In the past decade, considerable efforts have been made to develop semi-transparent organic solar cells (ST-OSCs). Different materials and architectures were examined with the aim of commercializing these devices. Among these, the use of ternary active layers demonstrated great promise for the development of efficient semi-transparent organic solar cells with the potential for future applications, including but not limited to self-powered greenhouses and powered windows. Researchers seek alternative solutions to trade-off between the power conversion efficiency (PCE) and average visible transmittance (AVT) of ST-OSCs, with photoactive materials being the key parameters that govern both (PCE) and (AVT), as well as device stability. Several new organic materials, including polymers and small molecules, were synthesized and used in conjunction with a variety of techniques to achieve semi-transparent conditions. In this review paper, we look at the working principle and key parameters of semi-transparent organic solar cells, as well as the methods that have been used to improve the performance and stability of ternary-based semi-transparent organic solar cells. The main approaches were concluded to be spectral enhancement and increments in the transparency of the active layer through band gap tuning, utilizing novel organic semi-conductors, optical engineering, and the design architecture of the active layers.

Semitransparent Organic Solar Cells with Superior Thermal/Light Stability and Balanced Efficiency and Transmittance

Semitransparent organic solar cells show attractive potential in the application of building‐integrated photovoltaics, agrivoltaics, floating photovoltaics, and wearable electronics, as their multiple functionalities of electric power generation, photopermeability, and color tunability. Design and exploration of semitransparent organic solar cells with optimal and balanced efficiency and average visible light transmittance and simultaneously high stability are in great demand. In this work, based on a layer‐by‐layer‐processed active layer and an ultrathin metal electrode, inverted semitransparent organic solar cells (ITO/AZO/PM6/BTP‐eC9/MoO3/Au/Ag) were fabricated. Optimal and balanced efficiency and average visible light transmittance were demonstrated, and simultaneously promising thermal and light stability were achieved for the obtained devices. The power conversion efficiency of 13.78–12.29% and corresponding average visible light transmittance of 14.58–25.80% were recorded for the ST‐OSC devices with 25–15 nm thick Ag electrodes, respectively. Superior thermal and light stability with ~90% and ~85% of initial efficiency retained in 400 h under 85 °C thermal stress and AM1.5 solar illumination were demonstrated, respectively.

Molecular design of cost-effective donor polymers with high visible transmission for eco-friendly and efficient semitransparent organic solar cells

Photoactive layer materials that overcome the trade-off between power conversion efficiency (PCE) and average visible transmittance (AVT) are required to prepare successful high-performance semitransparent organic solar cells (ST-OSCs). Among 12 novel cost-effective D–π=A polymers with high visible light transmission, P(3IN = 0.3)(3IN2F = 0.5)(BDD = 0.2) achieved a PCE of 14.0% and high stability in an eco-friendly solvent-processed OSC with BTP-eC9. This blend film exhibited an AVT of 62.1% and a color rendering index of 95.0, demonstrating the high potential for ST-OSCs. The ternary OSC with PM6 greatly enhances the PCE to 17.3%. Binary and ternary ST-OSCs achieve light utilization efficiencies (LUEs) of 4.38% and 4.04%, respectively, demonstrating the potential of the D–π=A structure. Under a 3000 K light-emitting diode light at 958 lx low illuminance, PCEs of 12.4% and 15.7% are obtained for binary and ternary ST-OSCs, respectively, and the indoor LUEs (LUIEs) of ST-OSCs are greatly enhanced to 5.52% and 5.48%, respectively. Air-processed eco-friendly ternary ST-OSC module (4.7 cm2) achieves not only a PCE of 12.1% and LUIE of 3.90% under 958 lx, but also color coordinates of (0.290, 0.323) and an infrared radiation rejection rate of 87.5%, meeting the civil engineering specifications for windows. This ST-OSC module can be a substitute power source of the thermo-hygrometer in real time, even operate at 195 lx, which paved the way towards zero-energy indoor and outdoor electrical devices as well as windows for buildings and vehicles.