Foldable Semitransparent Organic Solar Cells for Photovoltaic and Photosynthesis

Abstract

solution-processability, and lightweight property. [1][2][3][4][5][6] Recently, the power conversion efficiency (PCE) of a single-junction device based on binary photoactive layer system had surpassed the 15-16% boundaries for opaque OSCs and 11-12% boundaries for semitransparent OSCs (ST-OSCs), all of which were fabricated on rigid glass substrates. [7][8][9][10][11][12][13][14] Though the PCE had increased remarkably on rigid glass substrates, development of OSCs on flexible substrates particularly for flexible ST-OSCs still lagged behind. [15][16][17][18] To date, the highest reported PCE for flexible ST-OSCs with average visible light transmittance (AVT) of over 20% was just over 10%. [19] Greater attentions should be focused on the development of flexible ST-OSCs due to its promising potentials as power-generating windows/roofs in building-integrated photovoltaics and photovoltaic vehicles. Additionally, one needs to consider the foldability properties of flexible ST-OSCs if advanced applications in 3D curved surfaces (e.g., future foldable roofs in multifunctional selfpowered greenhouse) are to be realized. This situation drove the current works for foldable-flexible ST-OSCs (hereafter referred to as FST-OSCs).Over the years, studies on ST-OSCs and/or FST-OSCs have centered around materials design of the photoactive layer (design of novel donor/acceptor). [6,20,21] Generally, photo active layer is designed to readily absorb solar irradiation in the nearinfrared (NIR) to infrared (IR) region while being partially transparent in the visible light region. These IR-absorbing photoactive layers are particularly favorable for agricultural applications (e.g., common greenhouse) as sunlight in the visible light region can be predominantly transmitted for plants growth. In fact, solar irradiation located in the visible light region (370-740 nm) is mostly responsible for photosynthesis processes in plants for growth. [22] Through this, ST-OSCs and/ or FST-OSCs for photovoltaic and photosynthesis can be realized, proving the future potential of semitransparent devices as windows/roofs in multifunctional self-powered greenhouse.FST-OSCs have several key parameters similar to its rigid counterparts, such as efficiency, transparency, color, and color rendering property. The main distinct feature of FST-OSCs is its mechanical stability against extreme mechanical Semitransparent organic solar cells (ST-OSCs) have attracted extensive attention for their potential greenhouse applications. Conventional ST-OSCs are typically based on indium tin oxide (ITO) electrodes which suffer from mechanical brittleness. Therefore, alternatives for ITO are required for realization of foldable-flexible ST-OSCs (FST-OSCs). Herein, flexible poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) electrodes are prepared as ITO alternatives via polyhydroxy compound (xylitol) microdoping and acid treatment. As a result, flexible opaque OSCs based on PBDB-T-2F:Y6 photoactive system yield a high efficiency of 14.20%. The desirable optic...

Novel Bimodal Silver Nanowire Network as Top Electrodes for Reproducible and High‐Efficiency Semitransparent Organic Photovoltaics

“…These features offer specific applications in transparent architectures, ranging from smart windows to roofs, buildings, and greenhouses, thus opening new markets for OPVs. [ 1–9 ] Despite the tremendous advancement in the power conversion efficiency (PCE) of OPVs in recent years due to the development of novel semiconducting materials and device engineering, solution‐processable transparent conductive electrodes (TCEs) have been one of the critical components to realize fully printable semitransparent organic photovoltaics (ST‐OPVs). In recent reports, thin metallic films (Al, Au, Ag) were commonly used as the transparent top electrodes for state‐of‐the‐art ST‐OPVs, which are based on energy‐intensive evaporation processes and not compatible with the low‐cost roll‐to‐roll fabrication in the ambient environment.…”

Recent Progress on Advanced Optical Structures for Emerging Photovoltaics and Photodetectors

“…To realize semitransparency in OPVs and PSCs, one can manipulate the coverage, [ 35–43,161–163 ] thickness, [ 10–17,44–48,164,165 ] or bandgap of the active layer [ 2,8,9,18–24,49,50,166–168 ] or replace the opaque metal electrode with light‐transmitting media (e.g., metal nanowires, [ 44,46,51–56,169–171 ] transparent conducting oxides, [ 43,57–61,167,168,172–180 ] transparent conducting polymers, [ 40,62,63,181–184 ] graphene, [ 54,64,164,185 ] and carbon nanotube [ 65,186–188 ] ). Although the most convenient way to fabricate an ST‐PV is to decrease the thickness of the top metal electrode and, thereby, increase its transparency, [ 35,39,40,47,58,66–72,124 ] there is always a trade‐off between conductivity and transparency.…”

“…[ 2,8,9 ] Using thin metallic electrodes (<20 nm) and active layers that mainly harvest ultraviolet (UV) and near‐infrared (NIR) light has led to high‐performance semitransparent PVs (ST‐PVs). [ 10–17 ] The integration of new structures with low‐bandgap active layer materials has provided high‐performance visibly transparent OPVs. [ 18–24 ] For instance, Yang et al demonstrated an ST‐OPV having a PCE of 12% and an average visible transmittance (AVT) of 20% using a thin Au/Ag electrode and a strategy of transparent hole‐transporting frameworks.…”

“…Plot of PCE with respect to AVT for ST‐OPVs and ST‐PSCs reported in the literature. [ 1,9–12,15,17,18,20–22,24,33–110 ] …”

Ternary All‐Small‐Molecule Solar Cells with Two Small‐Molecule Donors and Y6 Nonfullerene Acceptor with a Power Conversion Efficiency over Above 14% Processed from a Nonhalogenated Solvent

“…A great deal of attention has been paid to bulk heterojunction organic solar cells (BHJ-OSCs) due to their distinctive advantages of low cost, light weight, easy fabrication, and flexibility for wearable devices. [1][2][3][4][5][6][7] In the past four years, nonfullerene smallmolecule acceptors (NFSMAs) [8][9][10][11][12][13] have been explored as replacements for fullerene (PC 71 BM and PC 61 BM) acceptors and this change pushed the power conversion efficiency (PCE) into the range 16-18% on using conjugated polymers as donors. [14][15][16][17][18][19][20][21][22][23][24][25] However, there is significant inconsistency in the device performance and this is caused by the batch-to-batch variations in the molecular weight and polydispersity index of polymer donors, which remain major challenges for the development of polymer-based solar cells.…”