Efficient Semi‐Transparent Organic Solar Cells with High Color Rendering Index Enabled by Self‐Assembled and Knitted AgNPs/MWCNTs Transparent Top Electrode via Solution Process

Abstract

conversion efficiency (PCE) has already exceeded 16% enabled by advanced photovoltaic materials. [3][4][5][6] Although opaque OSCs exhibit high efficiency, their usage is limited because they demand dedicated space and additional installation work on the roof, like traditional silicon solar cells. Therefore, the transparent property of OSCs was exploited for semi-transparent photovoltaic modules to extend their application in power-generating windows for buildings and automobiles. To fabricate efficient semi-transparent OSCs (STOSCs) with high average visible transmittance (AVT), [7] several approaches have been attempted for improving the visible light transparency of active layer, including molecular energy level modulating in non-fullerene acceptors, [8][9][10][11][12] usage of low-band gap organic semiconductors to shift absorption to near-infrared region, [13] fabrication of active layer with fiber network structure [14] and so on.On the other hand, developing transparent electrodes (TEs) with high conductivity to reduce the absorption/reflection in visible light without degrading interfacial contact is also equally important to achieve high-performance STOSCs. [2] Evaporated thin metal-based top electrodes were most reported to date due to their high conductivity and transparency. [15][16][17] However, the high cost and strict conditions of vacuum-deposited TEs are not suitable for large-area device fabrication and contradict the aim of renewable energy. [18] Furthermore, the transmittance of evaporated thin metal is not uniform throughout the visible region, resulting in low color-fidelity in STOSCs. [19] Therefore, in the past decade, scientists have advocated to develop solution-processed TEs, such as conducting polymers, [20][21][22] Ag nanowires (AgNWs), [23][24][25][26] graphene, [27][28][29][30] and carbon nanotubes (CNTs). [31][32][33][34] Nonetheless, the sheet resistance of polymers-based and carbon-based TEs is relatively high and even the lowest reported values to date is larger than 50 Ω sq −1 . Moreover, the acid treatment at high temperature for the conductivity enhancement of polymers adversely damages the underlying layers of OSC, [35][36][37] and hence complicated transfer process is required to be used as top TEs. [38,39] In addition, the unsatisfactory vertical conductivity of carbon materials and the stability issue of AgNWs and conducting polymers make them unappealing to be used in STOSCs. Semi-transparent organic solar cells (STOSCs) have attracted tremendous attention in power-generating windows for buildings and automobiles.Although STOSCs based on vacuum-deposited thin metal films exhibited power conversion efficiency exceeding 10%, solution-processed top transparent electrode (TE) is desirable for large-area and low-cost fabrication of STOSCs. Here, we present a self-assembled and knitted Ag nanoparticles/multi-walled carbon nanotubes composite thin film by solution process as transparent top electrode for STOSC. The composite film exhibits an extremely low sheet resistance of 14...

Recent progress in organic solar cells based on non-fullerene acceptors: materials to devices

“…This ST-OSC achieved a PCE of 7% with a high AVT of 36% and a colour rendering index of 90. 228 We further improved the PCE to 13.19% with AVT of 24.56% by using a ternary blend of PBDB-TF, Y6 and our in-house designed BDC-4F-C8. 229 Hou et al reported PBDB-T donor with IEIC-4Cl.…”

Recent Applications of Carbon Nanotubes in Organic Solar Cells

“…Interestingly, the MWCNT-based devices managed to retain above 80% of their original PCE after storage for 10 days under environmental conditions, and also managed to maintain their initial PCE, above 90%, after 100 bending cycles, demonstrating their superior long-term environmental stability and excellent flexibility. Recently, a relatively high PCE of 7% has been obtained after introducing Ag nanoparticles (NPs) into MWCNT-based anodes of inverted OSCs ( Zhang et al, 2021 ), demonstrating the significance of nanocomposites towards enhancing the efficiency of devices. In similar studies, but with conventional OSCs based on MWCNTs ( Mugadza et al, 2017 ) and DWCNTs ( Zhang et al, 2018 ), as anodes, more stable devices with optimum PCEs of 0.68 and 1.71%, respectively, were fabricated.…”

Recent Progress on Emerging Transparent Metallic Electrodes for Flexible Organic and Perovskite Photovoltaics

“…[ 81 ] The formation of oxide phases on Cu surface is detrimental to the electrical conductivity of the subsequent CuNW network. [ 82 ] To tackle these issues, a viable strategy is to adopt a composite of NWs with other nanomaterials such as conductive polymers (e.g., poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) or its variants), [ 83,84 ] metal oxides, [ 85,86 ] metals, [ 26,87,88 ] carbon nanotubes, [ 89–91 ] graphene, [ 81,92 ] or GO. [ 93,94 ] Furthermore, the incorporation of other nanomaterials into a metal‐based electrode can also offer considerable enhancement in other performance aspects such as enhanced electrode stretchability/conductivity, reduced surface roughness, [ 77,95–97 ] and corrosion protection for the adjacent layers in the cells.…”