A Commercial Benchmark: Light‐Soaking Free, Fully Scalable, Large‐Area Organic Solar Cells for Low‐Light Applications

Abstract

Low‐light applications provide an exciting market opportunity for organic solar cells (OSCs). However, so far, studies have only considered OSCs of limited commercial viability. Herein, the applicability of a fully‐scalable, flexible, inverted non‐fullerene acceptor (NFA) containing OSC is demonstrated by showing its superior performance to silicon under low‐light, achieving 40 µW cm−2 maximum power output at 1300 lx illumination. The effect of parasitic resistance and dark current on low‐light performance are identified. Furthermore, an atmosphere sensitive light‐soaking (LS) effect, critical for low‐light performance and resulting in undesirable S‐shaped current‐voltage characteristics, is analyzed. By employing different interlayers and photoactive layers (PALs) the origin of this LS effect is identified as poor electron extraction at the electron transport layer (ETL)/PAL interface when the common ETL ZnO is used. Two strategies are implemented to overcome the LS effect: replacement of ZnO with SnO2 nanoparticles to reduce ETL sub‐gap electron trap states or tuning the NFA energy levels to optimize interfacial energetics. Finally, the commercial viability of these LS‐free devices is demonstrated by fabricating fully printed large‐area modules (21.6 cm2) achieving a maximum power output of 17.2 µW cm−2, providing the most relevant example of the currently obtainable performance in commercial low‐light OSCs.

Indoor Organic Photovoltaics for Self‐Sustaining IoT Devices: Progress, Challenges and Practicalization

“…Recently, Luke et al investigated the low light IOPVs device performance of commercially feasible inverted device architecture, employing all solution processed R2R fabrication technique and relatively low-cost polymer (P3HT) donor and NFA (O-IDTBR) acceptor as active layer materials. [104] This is particularly important as thick layers are easier to manufacture by R2R processes (Figure 9a). Their results suggested that screening of possible low light OPV devices using 1 sun illumination is not appropriate, as some OPV devices that perform well at low light intensities may appear to not work well under standard illumination conditions.…”

“…Although, such interfacial reaction mechanisms can be stopped through effective passivation of metal ion doping or interfacial modification, the development of suitable interlayers with excellent performance and stability are prerequisite for the progress of high-performance and stable OPV devices. [104,114,115] Cui et al demonstrated the device stability of PBDB-TF:IO-4Cl based conventional OPV cell under continuous indoor light illumination (Figure 10a,b). [2] The OPV cells maintained their initial PCE after 1000 h that exhibits a great potential of OPVs for indoor applications with excellent device performance and operational stability.…”

Comparing and Quantifying Indoor Performance of Organic Solar Cells

“…Unfortunately, most publications lack in absolute data and only provide the relative spectral irradiance of their LED, [14,15,17,21,25,26,33,63] which is much easier to obtain, in some cases not even relative light source spectra are given. [24,34,64] Hence, in many publications the illuminance is determined by a lux meter [15,16,21,25,29,30,32] and then the input power density is calculated with the measured illuminance and the relative spectra of the light source. The lux meter, however, only really measures relative photon densities and converts those to irradiance values using an assumption about the spectral shape of the light source.…”

“…Although efficiencies for indoor organic photovoltaics (iOPV) [ 14–35 ] and other emerging indoor photovoltaics (iPV) technologies such as halide perovskites [ 36–43 ] or dye‐sensitized solar cells [ 44–50 ] have improved substantially, it is hard to quantify progress and determine champion solar cells due to a lack of standardized comparison methods. [ 12,51,52 ] Different authors use different conditions to evaluate the performance of their devices.…”

All-polymer indoor photovoltaic modules

“…To realize wireless and battery-free self-powered sensor nodes for practical applications, IPV is an attractive option because it harvests light energy from ambient conditions and generates electricity with high power output. Among the various IPV technologies, organic photovoltaic is most suitable because of its advantages of solution processing, flexibility, and the adjustable absorption spectra ( Song et al., 2020 ; Zhu et al., 2021 ; Luke et al., 2021 ; Ma et al., 2021b ; Cui et al., 2020a ). In the past several years, great progress has been made in organic IPV.…”