Disruptive Durable All-Polymer Solar Cells (FY2019-000119-AS)

Project: Research project

Project Details


To date, light-weight, flexible bulk-heterojunction polymer solar cell (BHJ-PSC) advances have been dominated by polymer donor + fullerene acceptor blend active layers. However this situation has changed dramatically with the advent of specific classes of non-fullerene molecular acceptors, and cell performance metrics such as power conversion efficiencies (PCEs) have soared to ~16% (literature projected: 20-25%) with 17% recently achieved by these Pis at Northwestern U. (NU). Nevertheless, polymer-small molecule blend photovoltaic structures have intrinsic morphological, thermodynamic, environmental, and mechanical instabilties and weaknesses. In contrast, all-polymer solar cells (APSCs) based on donor polymer + acceptor polymer blends have received far less attention and offer many untapped advantages. To date, PCEs have recently surpassed (by a small amount) the 10% benckmark and the NU team has already achieved ~ 9%. Moreover, fundamental polymer science and these initial results argue that, if curent materials synthesis and processing challenges are addressed, APSCs will provide: 1) High, tunable light absorption; 2) High PCEs and other photovoltaic metrics, perhaps equalling those of polymer donor + fullerene acceptor blends; 3) Robust BHJ film morphologies; 4) Long-term thermal, oxidative, and mechanical stability; 5) Compatibility with environmentally benign large module manufacture. To advance APSCs to the next level and achieve these objectives will require an integrated synthesis, processing, and characterization effort integrating three tasks: Task 1. Synthesize new block copolymer acceptors. The objectives of this task are: (i) Achieve good miscibility with retention of polymer transport characteristics; (ii) Use quinoidal polymer blocks to enhance light harvesting, with the best structures to be prepared in di/triblock versions. (iii) The most promising acceptors from I and ii will be refined by 2D molecular mass mapping, then transitioned to module fabrication. Task 2. Process and characterize blends and fabricate APSCs. The objectives of this task are: (i) Use finite element fluid simulations (stream-line representation) of the flow fields between microstructured printing blades and the substrate resulting in Laminar, Extensional, and Mixed flows. (ii) Optimize shear fields to achieve favorable polymer conformational changes, alignment, and pure domain formation in the shear field. (iii) Use polymeric additives, procssing techniques to further optimize APSC blend domain size and purity as assessed by solar cell photovoltaic reponse and R-SoXS measurements. Task 3. Fabricate APSC modules and establish cell performance-mechanical stress correlations. The objectives of this task are: (i) Fabricate and characterize the performance of APSCs fabricated with the most promising polymer-polymer blends on flexible substrates, progressing to a goal of 30 cm2 modules. (ii) Achieve these objectives using environmentally benign solvents and processing additives. (iii) Evaluate the mechanical and environmental stability properties of both free-standing blend films and modules fabricated from them.
This integrated attack should produce new sets of understanding-based polymers and polymer blends, and processing methodologies for them, as discussed above, for unprecedented APSCs with PCEs (PCE = 15% on glass; PCE = 12% as 30cm2 module) and other cell metrics approaching those of the best polymer-small molecule blends and with mechanically durable modules and superior environmental stability.
Effective start/end date2/1/201/30/24


  • Office of Naval Research (N00014-20-1-2116)

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