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The article delves into the critical factors affecting the commercialization of organic photovoltaics (OPVs), focusing on the cost of active layer materials and their impact on the levelized cost of electricity (LCOE). It introduces a methodology to survey active layer material pairs for commercial applications, emphasizing the importance of device efficiency, lifetime, and cost. The study highlights the significant cost reduction achieved through optimized synthesis protocols for the acceptor material ITIC, demonstrating the potential for competitive LCOE values even at modest efficiency and lifetimes. The research underscores the need for scalable material synthesis and provides valuable guidance for selecting materials suitable for upscaling in the OPV industry.
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Abstract
The field of organic photovoltaics (OPV) has delivered significant performance increases through the development of donor polymers and non-fullerene acceptors (NFAs). However, these improvements have come at the expense of increased synthetic complexity, reduced scalability, and consequently higher cost. By contrast, the development of commercial OPV technology requires scalable donor–acceptor materials, which can achieve a competitive levelized cost of electricity (LCOE). As such, if OPV technology is to become commercially viable, synthetic accessibility, quantification of cost, and active layer contribution to LCOE need to be considered. This paper presents three case studies examining the cost of materials (COM) for two polymer donors (poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PBDB-T) and poly[2,2⁗-bis[[(2-butyloctyl)oxy]carbonyl][2,2′:5′,2″:5″,2‴-quaterthiophene]-5,5‴-diyl] (PDCBT)), and one non-fullerene acceptor (NFA) (3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC)). Published synthesis procedures for these materials were investigated to determine laboratory-scale COM. This analysis revealed that the NFA was significantly more expensive (~five-fold) than the cheapest donor material. Consequently, the ITIC synthesis was experimentally optimized (ITIC-Exp), delivering a significant (~six-fold) reduction in COM. Finally, bulk-scale COM was calculated based on established cost scaling laws for speciality chemicals. The effect of laboratory- and bulk-scale COM upon the LCOE for OPV modules printed at commercial scale was determined. This work highlights the finding that, at laboratory scale, a COM of $60 g−1 represents a reasonable active layer cost benchmark for competitive LCOE. This study further reveals that at bulk scale, a highly competitive LCOE ($0.13–$0.08) is achievable for the optimal donor–acceptor pair (PDCBT-DArP:ITIC-Exp) at modest efficiency (3–5%) and lifetime (3–5 years).
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Introduction
The field of organic photovoltaics (OPVs) has experienced rapid growth during the last decade. This rapid growth has led to a record number of active layer materials published, pushing power conversion efficiency (PCE) to just short of 20%.1‐4 However, despite these rapid advances in material development and in device efficiency, the challenge of commercialization remains. A methodology for surveying active layer material pairs for viability in commercial applications is thus sorely needed. It is well established that commercial viability for OPVs is governed by three key parameters: device efficiency, lifetime, and cost.5 Historically, a ‘10–10’ target (10% efficiency–10-year lifetime) has been proposed for commercial viability of OPV.6 However, this goal ignores the fact that the true criterion for OPV commercialization is the levelized cost of electricity (LCOE) produced. The cost of input materials, for the active layer, electrodes, substrate, and barrier film, is an important component of the LCOE.7‐9 For the active layer, this cost can be represented by the cost of materials (COM), i.e. the sum of the cost of the individual materials consumed during manufacturing, which is a key component for OPV commercialization. Indeed, the progress/viability of printable solar modules in terms of wider metrics such as LCOE is already attracting a broad audience, with numerous recent high-quality publications and reviews.10‐12 However, few studies have investigated OPV material synthesis of active layer components with respect to COM and bulk-scale viability. As such, further efforts are needed to address the lack of research on upscaling and development of effective materials with low synthetic complexity.
In this study, the LCOE and the overall cost contribution of the active layer to the final device/module are detailed, using a methodology that allows for surveying the viability of active layer material pairs in commercial applications. The published synthetic procedures of the three active layer materials poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5-b′]dithiophene))-alt-(5,5-(1′,3′-di-2-thienyl-5′,7′-bis(2-ethylhexyl)benzo[1′,2′-c:4′,5′-c′]dithiophene-4,8-dione))] (PBDB-T), poly[2,2⁗-bis[[(2-butyloctyl)oxy]carbonyl][2,2′:5′,2″:5″,2‴-quaterthiophene]-5,5‴-diyl] (PDCBT), and 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC), forming the two high-performing active layer pairs of PBDB-T:ITIC and PDCBT:ITIC, have been investigated to determine the material cost per gram. In a new, holistic approach, the ITIC synthesis costs were determined for both the literature procedure (ITIC-Lit) and cost-optimized protocol (ITIC-Exp), which was experimentally verified at greater than 10 g scale. This approach enabled a direct comparison between literature and experimental data and contributed to a more accurate COM. Bulk-scale material costs were estimated,13 and the LCOE for each active layer combination was calculated as a function of lifetime and PCE, according to the model published by Mulligan et al.14 Calculating the LCOE in this manner allows for a detailed investigation of the trends and demonstrates the interplay between active layer material PCE, lifetime, and cost. Finally, a comparison of printed OPV with other electricity generation technologies revealed that for the PDCBT:ITIC system, highly competitive LCOE values are calculated at modest efficiency, lifetimes, and COM.
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Experimental
2.1. Material Selection
To determine the active layer material pairing best suited to commercial scale-up for OPV production, the published synthetic methods of approximately 200 donor and acceptor materials were screened for synthetic complexity (as defined by Po et al.15), economic viability, and efficiency. For the ten most promising material combinations, a simple figure of merit (FOM) was then calculated (see Supplementary Information) to rank material combinations in terms of viability:
where η is the maximum reported efficiency of the material combination, and \({\omega }_{D}\) and \({\omega }_{A}\), and \({SC}_{D}\) and \({SC}_{A}\), are the mass fraction of the donor and acceptor materials in the device active layer and the synthetic complexity (SC) scores for the donor and acceptor materials (these are divided by the maximum SC index of 100 for the highest complex material), respectively.
Based on this FOM analysis and experimental tractability in our laboratory, active layer combinations of PBDB-T and PDCBT (as donor materials) and ITIC (as the acceptor material) were chosen for this study. These material combinations have the advantages of reported PCE over 10% and a low number of total synthesis steps.
2.2. Laboratory-Scale Devices
Small-scale devices utilizing a configuration of glass/ITO/PEDOT:PSS/PDCBT:ITIC (1:1)/ZnO/Al were fabricated and tested to obtain benchmarked device efficiencies for LCOE calculations. Full experimental details are provided in the Supplementary Information. This architecture was chosen since it is compatible with large-scale roll-to-roll processing by substituting the substrate and ITO electrode for PET with a silver grid (Ag) electrode.16,17
2.3. Cost Calculations
From the literature, PBDB-T, PDCBT, and ITIC can be prepared via 8–10-, 5–6-, and 5-step procedures, respectively, as outlined in the Supplementary Information.18‐28 Typically, more synthetic steps tend to correlate to increased synthetic complexity and in turn higher cost.29 It is therefore expected that the 5-step synthesis of PDCBT via direct arylation polymerization (PDCBT-DArP) will carry a lower cost than the 6-step synthesis route utilizing Stille coupling (PDCBT-Stille) as the polymerization method. The synthesis cost of these three materials was calculated according to published literature procedures, using estimations from Osedach et al.29 wherever weights and volumes could not otherwise be obtained. To easily track the origin of high-cost items/procedures, the calculated costs were divided into reaction (R) costs and purification/work-up (WU) costs.
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The COM for all the active layer materials was calculated based on the consumption of reactants, reagents, catalysts, solvents, drying agents, and silica. However, costs for labour, electricity, washing consumables, equipment, glassware, filters and filter papers, and waste disposal were excluded from the calculations. The literature procedures were assumed to be linearly scalable, and material consumption was calculated per gram of final product for each of the steps in the published synthetic procedures. In the cases where information regarding the materials consumption was not available, estimates for extraction, column chromatography, drying, and recrystallization from Osedach et al., outlined in Table SI2, were used. Based on previous work conducted on the synthesis of P3HT, it was estimated that 3 L of each purification solvent is needed for the Soxhlet extraction of 100 g of polymer. For the complete list of the material consumption for both experimental and literature procedures, refer to the Supplementary Information.
Prices for materials were determined by collecting commercial quotes. The quotes were restricted to smaller quantities to better reflect the current cost at a laboratory scale (i.e. no bulk pricing). Preference was given to larger, well-known suppliers such as Merck, Bio-Strategy, and Thermo Fisher Scientific. Smaller suppliers with an established business relationship with the Centre for Organic Electronics were also given preference over unknown entities. A complete list of quotes, with prices given in original currencies, is provided in the Supplementary Information.
The COM of the active layer materials could then be calculated for both literature and experimental procedures by multiplying the price, as determined through the collection of commercial quotes, by the sum of the volume/weight of each of the reactants, reagents, catalysts, solvents, drying agents, and silica consumed per gram of final product synthesized. All calculated costs are in US dollars.
2.4. LCOE Calculations
LCOE calculations were conducted according to the method published by Mulligan et al. in 2014.14 All the values from this original publication were carried forward except for those related to synthetic equipment and active layer material costs. The costs for the active layer materials were updated according to the calculated material costs for ITIC-Lit, ITIC-Exp, PBDB-T, PDCBT-Stille, and PDCBT-DArP. The added synthetic complexity when switching from P3HT:PCBM to PBDB-T:ITIC or PDCBT:ITIC is estimated to incur equipment costs that are at least 150% higher, as the total number of reaction steps increases by 150% and the work-up steps increase by an even greater factor in the case of ITIC-Exp:PDCBT-DArP. To allow for a margin of error, it was assumed that equipment costs tripled when switching the active layer pair. This cost increase was used in the LCOE calculations for all active layer pairs to simplify the procedure.
Results and Discussion
3.1. Literature Material Costs at Laboratory Scale
The literature-based COM were calculated for ITIC (ITIC-Lit), PBDB-T, PDCBT-Stille, and PDCBT-DArP following the method described in the Experimental section, and the results are presented in Table I. ITIC-Lit was by far the most expensive out of the three materials, with a total cost of about $320 g−1, despite having the shortest synthesis route. This high cost is likely a result of the low overall yield of 10.54% for ITIC-Lit. For the donor polymers, higher overall yields of 23.92%, 30.83%, and 33.72% were calculated for PBDB-T, PDCBT-Stille, and PDCBT-DArP, respectively, and the lower $ g−1 costs for these materials reflect these higher yields.
Table I
Literature-based cost estimates for the acceptor ITIC and the donor polymers PBDB-T and PDCBT (Stille and DArP synthesis routes)
ITIC-Lit
PBDB-T
PDCBT-Stille
PDCBT-DArP
Synthesis steps
5
10
6
5
Reaction [$ g−1]
131.74
47.31
28.38
16.41
Work-up [$ g−1]
186.47
81.07
64.60
46.70
Total [$ g−1]
318.21
128.38
92.98
63.11
3.2. Experimental Cost Optimization of ITIC Synthesis at Laboratory Scale
The literature-based cost estimates (Table I) reveal that ITIC is the most expensive material (by approximately a factor of 3–5) and therefore offers the greatest potential for cost improvement through modification of the synthesis, since published literature procedures are not typically developed with a focus on cost. For example, our initial analysis of the literature synthesis of ITIC showed that disproportionally large volumes of solvents are used in key purification processes (column chromatography, washings, extractions, and precipitations).
To address this issue, a framework for the cost optimization of the synthesis was developed based on the reaction scheme and the material purification (Fig. 1). Optimization of the purification processes was prioritized within the framework, reflecting their high contribution to the overall cost. For each process, a hierarchy of controls were explored, from elimination (e.g. of purification or low yield reaction steps) to substitution/prioritization (e.g. with lower cost purification of later reaction steps) to optimization (e.g. of solvent concentrations for purification and reactions).
Fig. 1
Visualization of the hierarchy of actions, with the targeted procedures in the top of each box and subsequent actions presented in order of importance underneath. The flow chart reads left to right for the targeted procedures and top to bottom for the related actions.
The framework was then applied to the 5-reaction-step synthesis of ITIC (Fig. 2). The major changes resulting from this process are summarized in Table II. For example, reaction steps 1, 2, 3, and 5 were conducted at higher concentrations, thereby reducing the volume of solvent needed. In addition, the chromatography processes used in reaction steps 1, 2, and 5 were optimized, significantly reducing the amount of both mobile and stationary phase compared to the literature procedure. The crude material obtained in step 3 was carried forward to step 5 in the reaction sequence, eliminating a purification step. 1H nuclear magnetic resonance (NMR) of the step 4 crude material did not show any impurities, and so the crude was also carried forward, eliminating the need for another purification step.
Fig. 2
Synthesis scheme for ITIC-Exp following experimental optimization according to the presented optimization framework.
Summary of the major changes to the synthesis procedures as well as the differences in yield between experimental and literature procedures
ITIC reaction step
Yieldlit (%)
Synthesis procedure change
Yieldexp (%)
Reaction
Purification
1
83
Concentrated reaction solution
Optimized chromatography
96.4
2
65
Concentrated reaction solution
Optimized chromatography
58.1
3
93
Concentrated reaction solution
Eliminated (crude carried forward)
n/a
4
85
No change
n/a
100
5
21
Concentrated reaction solution and lowered equivalent of reactant
Optimized chromatography
n/a
3 and 5
19.5
59.8
Overall
10.5
33.5
Overall, a yield of 33.5% was achieved for the optimized synthesis of ITIC, significantly higher than the reported literature yield of 10.5%. A comparison of the in-house synthesized ITIC-Exp to the commercially acquired ITIC-1M with 1H NMR revealed identical spectra with no apparent impurities (see Supplementary Information).
A cost analysis of the revised ITIC synthesis reveals a significantly reduced material cost of $58.21 g−1, which is about six times lower than the calculated literature cost ($318.21 g−1), demonstrating that optimization of experimental procedures can be highly effective in reducing material costs. The largest single contribution to this cost discrepancy is the difference in yield across reaction steps 3 to 5, with the literature yield less than a third of the revised value reported here. It is however remarkable that when the yields of the literature procedures for step 3 and step 5 are entered into the model for ITIC-Exp a low cost of $166.07 g−1 and an overall yield of 11.76% is achieved. This cost still represents a significant reduction (~50%) compared to the literature procedure and is the result of reduced solvent consumption due to optimization of the purification steps. It can thus be concluded that solvent use is a significant cost driver regardless of yield and that a combination of improved yield and experimental improvements contribute to the significant COM reduction.
In order to compare our data with commercial pricing, quotes from both larger companies and niche manufacturers were acquired, with pricing varying significantly for the speciality materials. Specifically, the quoted prices for ITIC started at $560 g−1 with the most expensive costing $6338 g−1. For PBDB-T and PDCBT the quotes ranged from $1450 g−1 to $4387 g−1 and $1450 g−1 to $4448 g−1, respectively. As such, it would appear that the COM only contribute to a small portion of the overall commercial price.
Calculated Bulk Material Costs
The commercialization of OPV necessarily involves the bulk synthesis of speciality materials, and thus the bulk material costs are an important factor in determining the overall commercial viability of the technology. One approach to determining the bulk material costs for the active layer donor and acceptor materials is to model a full chemical synthesis plant and associated chemical reactions needed to produce each material at scale. Previously, this approach was taken by Mulligan et al., who showed that at the 100-tonne-per-annum scale, the anticipated bulk material costs for P3HT and PCBM were $1.18 g−1 and $13.70 g−1, respectively.9
An alternative approach for calculating bulk costs of speciality materials is to follow the methodology developed by Hart and Sommerfeld.13 This methodology allows for the bulk selling price of speciality chemicals to be estimated from a single data point using Equation 2.
In this equation, PB is the estimated bulk price, P1 is the unit price in $ kg−1 and Q1 is the quoted amount in grams. For this model, QB is the bulk quantity of 60 lb (27,216 g) and bavg is a constant of − 0.75.13
Applying this methodology to the presented cost analysis data, the bulk cost of the active layer materials can be estimated. For this estimate the bulk price and unit price have been replaced with bulk cost (CB) and unit cost (C1), with the assumption that the cost price scales similarly to selling price. Q1 was set to 100 g to reflect the size of large laboratory-scale batches. Both the laboratory-scale and bulk costs for each material are presented in Table III and show that at bulk-scale a much lower cost of $0.87 g−1 and $0.94 g−1 is reached for ITIC-Exp and PDCBT-DArP, respectively, a significant decrease from the laboratory-scale scenario.
Table III
Summary of cost estimations for both laboratory-scale and bulk-scale manufacturing of ITIC-Exp, ITIC-Lit, PBDB-T, PDCBT-Stille, and PDCBT-DArP. The quoted amount, or in this case laboratory-scale, Q1 was set to 100 g and the bulk-scale, QB to 27,216 g. These two constants are not included in the table
ITIC-Exp
ITIC-Lit
PBDB-T
PDCBT-Stille
PDCBT-DArP
Laboratory-scale [$ g−1]
58.21
318.21
128.38
92.98
63.11
Bulk-scale [$ g−1]
0.87
4.75
1.92
1.39
0.94
Benchmarking Photovoltaic Performance of Experimentally Optimized ITIC
In order to benchmark the experimentally optimized ITIC material, the solar cell device performance of the PDCBT:ITIC active layer devices was measured using both commercial (ITIC-1M) and in-house synthesized ITIC (ITIC-Exp). All devices were fabricated in a roll-to-roll compatible device configuration of glass/ITO/PEDOT:PSS/PDCBT:ITIC (1:1)/ZnO/Al, using commercial PDCBT donor polymer. The device data tabulated in Table IV show that the hero devices achieved power conversion efficiency (PCE) of 7.25% and 6.94% for ITIC-1M and ITIC-Exp, respectively. A box plot showing variations in device parameters and the current density–voltage (J–V) curves for the hero devices are shown in Figure SI2 and Figure SI3, respectively. For the hero devices, a short-circuit current density (JSC) of 13.0 mA cm−2 was measured for ITIC-Exp, with a slightly lower JSC of 12.4 mA cm−2 measured for ITIC-1M. For the average device data, the lower current combined with a reduced fill factor (FF) resulted in the PCE for the ITIC-Exp material being marginally below that of its commercial counterpart. However, a good match in open-circuit voltage (VOC) over the 10 devices is observed, consistent with the ultraviolet–visible (UV–Vis) results (Supplementary Information). Overall, the performance of the two ITIC materials is in good agreement, validating the purity of the ITIC-Exp material.
Table IV
Device characteristics for PDCBT:ITIC for commercially sourced PDCBT and varying ITIC batches. Data are presented for hero devices, with the mean values with standard deviation given in parentheses. The mean and standard deviation values were calculated for a minimum of 10 devices
Active layer
JSC (mA/cm2)
(FF)
VOC (V)
PCE (%)
PDCBT:ITIC-1M
12.4 (11.7 ± 1.3)
0.63 (0.58 ± 0.05)
0.92 (0.91 ± 0.01)
7.3 (6.2 ± 0.5)
PDCBT:ITIC-Exp
13.0 (10.7 ± 1.0)
0.58 (0.55 ± 0.02)
0.92 (0.91 ± 0.01)
6.9 (5.4 ± 0.6)
LCOE
Mulligan et al. provided a detailed assessment of the LCOE of OPV modules [2015] based on a techno-economic assessment (TEA) of an industrial manufacturing plant for OPV donor and acceptor materials [2014]. The attractiveness of this model is that it then uses the bulk COM of the speciality donor and acceptor pair as an input to calculate module cost and, consequently, LCOE as a function of module efficiency (η) and lifetime (τ). Unlike the work published by Mulligan et al., where a factory producing 100 tonnes per annum was modelled, this work determines the COM by calculating the laboratory-scale cost of speciality donor and acceptor materials and then applies the adjustment for large-scale synthesis proposed by Hart and Sommerfeld (Fig. 3).
Fig. 3
Flow schematic of the LCOE model as a function of power conversion efficiency and lifetime (LCOE(η, τ)) developed by Mulligan et al.9 In the original work, the bulk COM was calculated by modelling a synthetic industrial plant (‘industrial plant model’), whereas in this work the bulk COM is determined using the Hart and Sommerfeld cost scaling ('cost estimate model’).
The calculated LCOE for modules utilizing the lowest-cost donor–acceptor active layer (PDCBT-DArP:ITIC-Exp) is presented in Fig. 4, as a function of module efficiency and lifetime for both laboratory-scale ($60.66 g−1 active layer) and bulk-scale ($0.91 g−1 active layer) COM (device architecture described in Supplementary Material, Figure S11). As first demonstrated by Mulligan et al., the effect of increasing efficiency and lifetime quickly diminishes for values exceeding 5% and 5 years, respectively.14 Moreover, comparing Fig. 4A and B, we see that the effect of the reduced COM of the bulk-scale active layer upon the absolute LCOE values also decreases with increasing module efficiency and lifetime. This observation highlights the fact that, in this case for printed OPVs, above a threshold of around 3–5% efficiency and 3–5-year lifetime, the other contributors to the LCOE (e.g. balance of systems) dominate.
Fig. 4
Effect of varying efficiency and lifetime on LCOE ($ kWh−1) for (A) laboratory-scale PDCBT-DArP:ITIC-Exp donor–acceptor COM and (B) bulk-scale PDCBT-DArP:ITIC-Exp donor–acceptor COM. The shaded regions of the table correspond to LCOE cost thresholds as follows: LCOE > $0.20 kWh−1 (red-shaded region), $0.20 kWh−1 < LCOE < $0.10 kWh−1 (yellow shaded region) and $0.10 kWh−1 > LCOE (green shaded region) to guide the eye (Color figure online).
As shown in Fig. 5, the bulk-scale LCOE results compare favourably with those for other electricity generation technologies. Figure 5 shows the LCOE for bulk-scale PDCBT-DArP:ITIC-Exp donor–acceptor COM for efficiencies of 2, 3, 5, and 10% and lifetimes of 2, 3, 5, and 10 years. These values are compared against the latest US-focused LCOE data taken from the 2023 Lazard report.30 Printed OPV devices with 3% efficiency and 3-year lifetime (upper red dashed line) compete favourably with residential conventional rooftop PV and nuclear- and gas-powered electricity generation. Further, by improving efficiency and lifetime to 5% and 5 years, respectively (lower red dashed line), printed OPVs begin to compete with wind and PV generation at utility scale. Given that printed OPV is a behind-the-meter technology, the comparison is made more favourable when transmission costs for utility-scale electricity are included, since these costs are not included in the scope of the Lazard report.
Fig. 5
US-focused LCOE data for various electricity generation technologies 30 compared with that of printed OPV technology with bulk-scale PDCBT-DArP:ITIC-Exp active layer for various power conversion efficiencies. The boundaries of the shaded OPV regions correspond to the LCOE values for 2-, 3-, 5- and 10-year lifetimes. The upper dashed red line shows the LCOE value for a printed OPV with 3% efficiency and 3-year lifetime. The lower dashed red line shows the LCOE value for a printed OPV with 5% efficiency and 5-year lifetime (Color figure online).
Overall, this work demonstrates that OPV active layer materials do not necessarily need to have the highest efficiency, longest lifetime, or lowest synthetic cost to be commercially viable. Indeed, based upon the model, active layer material combinations of $60 g−1 or cheaper that achieve 3–5% efficiency or better and last for 3–5 years or longer can deliver competitive LCOEs. Specifically, at $60 g−1, active layer materials achieve LCOEs of $0.19 and $0.11 for efficiency/lifetime combinations of 3%/3 years and 5%/5 years, respectively. These LCOE values lie within the range for rooftop PV at the higher end and are cheaper than gas/nuclear and within the LCOE range of coal at the lower end.
Thus, this study provides a reasonable target benchmark cost for active layer material combinations, with only modest efficiencies at laboratory scale. While for some OPV materials this target is already achievable, this paper shows that for a synthetically complex material such as ITIC, this target cost can be achieved through judicious optimization of the synthetic protocols. However, for a truly commercial-scale OPV technology, these materials must be capable of synthesis at bulk scale, whereupon further reductions in LCOE may be achieved. As such, this work highlights that a key criterion for commercial viability is the scalability of OPV material synthesis, and thus, increased effort is required to develop the at-scale synthesis of donor polymers and non-fullerene acceptor materials. Furthermore, these research efforts are likely to focus on low- to mid-complexity materials that have clear paths to upscaling, thereby excluding more complex materials, e.g. Y6, from any near-term commercialization efforts. This in turn implies that, as previously stated, the chase after record efficiencies is misguided, and may even prove detrimental to future commercialization efforts.
Conclusion
The material costs for ITIC-Lit, PBDB-T, PDCBT-Stille, and PDCBT-DArP were calculated using published literature procedures, and the COM was also determined experimentally for ITIC-Exp. The large cost discrepancy between ITIC-Lit ($318.21 g−1) and ITIC-Exp ($58.21 g−1) was attributed to differences in yields as well as significant experimental improvements for ITIC-Exp. The calculated cost data show that the most promising active layer pair combination was PDCBT-DArP:ITIC-Exp. Consequently, small-scale devices were manufactured utilizing a roll-to-roll compatible device configuration, with commercially acquired PDCBT and ITIC (ITIC-Exp) for benchmarking purposes. A highest PCE of 6.94% was achieved for the hero device, which agreed with reference devices made with commercially acquired ITIC.
The material costs for the PDCBT-DArP:ITIC-Exp active layer pair were used to calculate the LCOE as a function of lifetime and efficiency and show that LCOEs competitive with existing electricity generation technologies can be achieved, even for laboratory-scale synthesis costs of these materials. These calculations reveal that active layer material cost of ~ $60 g−1 coupled with modest module efficiencies (3–5%) and lifetimes (3–5 years) yields LCOE values that are competitive with most existing electricity generating technologies. Interestingly, improvements in the LCOE rapidly tapered off with increasing PCE and lifetime as well as COM.
As such, this work demonstrates that the commercialization of organic photovoltaics does not rely on high efficiencies, long lifetimes, or low COM, but instead on the viability of large-scale manufacturing of the active layer materials. Indeed, materials that are easily synthetically accessible with low synthetic complexities and moderate efficiencies appear to be the most likely candidates for commercialization of OPV.
Importantly, the results presented in our paper provide the first objective guide to the choice of what materials are suitable for upscaling. This guidance is an important contribution when considering the significant time and resources that are required to commercialize a new technology. In the case of OPV the cost of materials and consumables alone make this a daunting task and hence careful selection of target materials is required.
Acknowledgments
This work was performed in part at the Materials Node (Newcastle) of the Australian National Fabrication Facility (ANFF), which is a company established under the National Collaborative Research Infrastructure Strategy to provide nano- and microfabrication facilities for Australia’s researchers.
Conflict of interest
The authors declare that they have no conflict of interest.
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